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Feed Additives
Dairy Nutrition Management
0749-0720/91 $0.00
+ .20
Feed Additives
Michael Francis Hutjens, BS, MS, PhD*
A feed additive can be defined as a feed ingredient or group of feed compounds that produces a desirable animal response in a nonnutrient role (such as a protein, mineral, or vitamin). Some feed additives may contain nutrients (such as sodium in sodium bicarbonate or methionine in zinc methionine) . Feed additives have gained attention and use due to higher milk yields, emphasis on milk components (especially milk protein), greater stress on milk cows, new research results, and extensive advertising by manufacturers. A 1983 field survey (Richetts R, personal communication, 1987) of additives used in herds producing over 9090 kg of milk found buffers, yeast, beta-carotene, niacin, methionine, and no additives were used on 62,17,16,3 and 10% of the farms, respectively. A 1987 survey of New York DHI (Dairy Herd Improvement) herds is summarized in Table 1 (Chase LE, personal communication). Feed additives are not a must or guarantee for higher milk yield or improved herd health. I
EVALUATING FEED ADDITIVES One method for evaluating a feed additive is to determine whether it satisfies four key factors: response, returns, research, and results. 28 Response refers to expected or performance changes the user could expect when a feed additive is included. • • • • • • • • •
Increase milk yield (peak milk and/or milk persistency) Increase in milk components (protein and/or fat) Increase dry matter intake Maintain a desirable rumen pH Stimulate rumen microbial synthesis of protein and/or volatile fatty acid (VFA) production Increase rate of passage or How of nutrients out of the rumen Improve fiber digestion in the rumen Stabilize rumen environment Improve growth (gain and/or feed efficiency conversion)
*Professor of Animal Sciences and Extension Dairy Specialist, Department of Animal Sciences, University of Illinois College of Agriculture, Urbana, Illinois Veterinary Clinics o/North America: Food Animal Practice-Vol. 7, No.2, July 1991
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I!!!!
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MICHAEL FRANCIS HUTJENS
Table 1. Use o/Feed Additives in 5700 Herds Whose Records are Processed at the New York DHI Computing Facility CURRENTLY
DISCONTINUED
USING
USING
PRODUCT
(%)
(%)
Buffers Ionophores Yeast Niacin Isoacids
67.6 35.4 17.2 14.4 13.0
23 8 49 30 62
• Minimize weight loss • Reduce heat stress effects • Improve health (such as less ketosis, reduced acidosis, or improved immune response) The veterinarian, consultant, nutritionist, or dairy manager should determine which responses to expect before adding the additive. Returns reflect the profitability of using a selected additive. If milk improvement is the measurable response, Table 2 can be used to determine break-even points. For example, a veterinarian recommends an additive that raises feed costs $0.10 per day. If milk is valued at $0.12 per 0.45 kg, every cow must produce 0.4 kg more milk to cover the added cost associated with the additive. Another consideration is if all cows receive the additive, but only those cows fresh fewer than 100 days respond. These responding cows must cover the additive costs for all cows (responsive and nonresponsive cows). For some responses (such as improved health or reduced stress) it is difficult to determine an objective economic value or an economic value that will be returned in the next lactation. One guideline is that an additive should return two dollars or more for each dollar invested in the additive; this covers nonresponsive cows and field conditions that could minimize the anticipated response. Other dairy managers feel the economic response to an additive must only cover the cost of the additive to be justified. Research is essential to determine whether experimentally measured responses can be expected in the field. Studies should be conducted under controlled and unbiased conditions, have statistically analyzed results (to determine whether the differences are reproducible), and be conducted under experimental designs that are similar to field situations (feed ingredients, feed delivery systems, level of milk yields, and various stages of lactation).
Table 2. Break-even Milk-yield Responses to Cover Additive Cost MILK PRICE
Additive Cost ($/cow/day)
10
0.02 0.06 0.10 0.30
0.1 0.3 0.5 1.4
($/45
ICG)
12 14 Milk increase needed (kg/day)
0.1 0.2 0.4 1.1
0.1 0.2 0.3 1.0
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FEED ADDITIVES
Results obtained on individual farms are the economic payoff. Dairy managers and veterinarians must have a data base to compare and measure responses. Several tools to measure results include DHI milk records (peak milk, persistency, milk components, and milk curves), reproduction summaries, somatic cell count data, dry matter intake, heifer growth charts, and herd health profiles that will allow critical evaluation of a selected additive. The remainder of this article discusses feed additives applying the four key factors. Veterinarians should be able to objectively decide when and how to select and use various products. BUFFERS The ruminant animal has a complex acid-base regulating system, with the rumen varying in pH from 5.5 to 7. Rumen pH has been directly related to rumen VFA concentrations, a function of rumen microbial degradation of organic matter, water flux across the rumen, rumen flow rates, saliva flow, and feed acidity. If rumen pH is not optimal, dry matter intake will decrease, acidosis can cause health problems, and microbial yield of protein and energy decreases. The addition of dietary buffers to control rumen pH can be justified if bunk management and nutritional factors cause low pH. Successful applications 14 Qf buffers result in higher feed intake, increased milk yield, and favorable milk composition (Table 3). Evaluating Buffer Compounds Buffers are widely used in dairy feeding programs. Chemically, buffers are a combination of a weak acid and its salt. Such combinations resist changes in pH or hydrogen ion concentration. To function properly, the buffer must be water soluble (calcium carbonate is not) and its equivalence point (pKa) must be near the physiologic pH of the rumen. Sodium bicarbonate is a true buffer, with a pKa of 6.25. Other compounds, called alkalinizing or neutralizing agents, increase the pH of the rumen fluid; one example is magnesium oxide. Several commonly used products are discussed and summarized in Table 4. 14,53 Sodium bicarbonate (bicarb) is a white crystalline compound derived from soda ash. It is 99% sodium bicarbonate (NaHC0 3 ) and GRAS listed (generally recognized as safe). The pH of a 1 % solution is 8.4 and it buffers at a pH of 6.2. Soda ash is produced from trona mineral. Bicarb is widely used as a buffer and has been thoroughly researched. Research has shown it to increase rumen pH and osmolarity, produce a more desirable rumen fermentation, and increase rumen fluid outflow. Sodium sesquicarbonate is a relatively new product sold under the trade name S-Carb (FMC Agricultural Chemical Group, Philadelphia, PA). It contains a mixture of sodium bicarbonate and sodium carbonate (an alkalinizing agent). The pH of a 1% solution is 9.9. It is a white, needlelike crystal product and GRAS listed. Six published experiments with sodium sesquicarbonate reported an increase of 1.6 kg milk and 0.23% milk fat compared to control COWS. 53 The price of sodium sesquicarbonate is typically lower than sodium bicarbonate. Alkaten (Church and Dwight Co., Inc., Princeton, NJ) is sodium sesquicarbonate, but contains about 6% inert materials, is slightly lower in sodium, and is not as refined. Trona also is sodium sesquicarbonate, but contains 10% inert material (dolomitic marlstone, shale, shortite, mudstone, and other products). Research work on trona has been limited. The presence of substantial amounts of foreign material in trona should be monitored in future experiments.
~
c:J1
00
+0.1 -1.1
+0.3 +0.6
3 6 11 9
+0.2 +0.2 +0.6 -0.1 0 +0.3
55 14 17 8 3 8
(NUMBER)
From Erdman RA: Dietary buffering requirements of the lactating dairy cow.
Magnesium oxide Adequate forage Low forage
Potassium carbonate Potassium bicarbonate
Sodium bicarbonate Adequate forage Low forage Corn silage Alfalfa hay Alfalfa/grass silage Alfalfa silage & corn silage
COMPOUNDS
STUDIES
Milk Yield (kg)
+0.05 +0.15
+0.16 +0.95
-0.01 +0.04 -0.02 -0.06
+0.05 +0.22 +0.07 -0.07 +0.04 NA
(units)
pH
Rumen
-0.04 +0.06 -0.02 NA +0.01 +0.04
Milk Protein (%)
CHANGES FROM CONTROLS
J Dairy Sci 71:3246, 1988; with permission.
+0.16 +0.35
+0.40 +0.45
+0.1 +0.28 +0.16 +0.03 -0.03 +0.10
Fat Test (%)
Table 3. Production Comparisons of Various Compounds from Published Research Studies with Different Forage Sources
-0.1 -1.8
+1.3 -0.1
+0.2 -0.1 +0.5 -0.1 +0.2 +0.2
Dry Matter (kg)
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Table 4. Composition and Characteristics of Buffers and Alkalinizing Agents for Ruminant Animals ITEM NaHC03 (%) N~C03 (%)
NAHC03
S-CARB
ALKATEN
TRONA
100.0
37.0 47.0
34.8 43.8
33.6 42.2
16.0 30.4
14.9 6.1 28.5
14.0 10.0 26.0
6.25
6.25 10.25
6.25 10.25
6.25 10.25
7
13
13
13
Source dependent
12
13
13
11
50
Water of hydration (%) Inert material (%) Sodium (%) Magnesium (%) pKa Solubility (g/100 mL) Acid-consuming (mEqJkg)
27.4
MGO
54 None
From Erdman RA: Dietary buffering requirements of the lactating dairy cow. J Dairy Sci 71:3246, 1988; Staples CR, Lough DS: Efficacy of supplemental dietary buffers for lactation cows. In Florida Nutrition Conference Proceedings, 1987; with permission.
Magnesium oxide (mag ox) is used as a source of magnesium (54%) and as an alkalinizing agent. Mag ox appears to regulate rumen fermentation and improve uptake of milk fat precursors by the mammary gland. 3 Solubility, heat treatment, and particle size can affect the action of mag ox. Calcium carbonate (limestone or CaC03 ) has little if any buffering action in the rumen. It can increase fecal pH when high starch diets are fed by increasing starch digestion in the small and large intestines and improving starch-splitting enzyme activity. Adding limestone to diets above 0.6 to 0.8% calcium has provided little beneficial effect. 12 Sodium bentonite, a clay mineral, is used as a pellet binder by the feed industry and is found in some buffer packs. It can prevent milk fat depression by shifting VFA patterns. It also swells in the rumen (5 to 20 times its size), adsorbs and exchanges minerals and ammonia, and may add bulk to the ration. Several other products are being used as buffers or in buffer packs. Potassium carbonate, potassium bicarbonate, magnesium carbonate, and sodium carbonate provide action similar to sodium bicarbonate. Potassium salts can be beneficial under heat stress and in low potassium diets, but are more expensive and less available commercially. The carbonate forms are alkalinizing agents and are generally unpalatable. Suggested levels of buffers and alkalinizers are listed in Table 5. Palatability of most buffers is low and requires careful management to avoid reduced feed intake. Buffer Use Strategies The key question in buffer usage is when dairy managers and nutritionists can expect an economically favorable response to buffers. The following is a list of conditions in which a positive response to buffers may be anticipated. 1. High corn silage diets. These are high in moisture (60 to 70%) and fermentable carbohydrate (over 30%) and low in pH (3.9 to 4.2). Optimal silage pH is 5.6 for maximum intake. 39,49 Corn silage has a shorter particle size
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MICHAEL FRANCIS HUTJENS
Table 5. Feeding Recommendations of Commonly Used Products for Lactating Cows PRODUCT
Sodium bicarbonate Sodium sesquicarbonate Magnesium oxide Sodium bentonite Calcium carbonate Potassium carbonate
LEVEL (G/DAY)
110-225 160-340 50-90 450-900 115-180 270-410
From Hutjens MF: Applications of rumen buffers and buffer packs in dairy nutrition. In Applications of Nutrition in Dairy Practice. Wayne, NJ, American Cyanamid, 1988, p 44; with permission.
due to more precise chopping and requires less salivation due to its wet nature. Buffering capacity of corn silage from pH 4 to 9 is 476 mEqfkg dry matter compared with alfalfa hay at 822 mEqfkg and timothy hay at 511 mEqfkg dry matter.l4 2. Wet rations. Diets with over 50% moisture depress total dry matter intake 6 to 9% if the wet feed has been fermented. Water per se does not depress dry matter intake (as with pasture or green chop). 3. Lower fiber rations. Those below· 19% acid detergent fiber (ADF) depress rumination and lead to rumen acidosis. Maryland researchers 14 suggest that a 1% increase in ADF (above 14%) increases fat test 0.145 percentage points and 108 g of bicarb and 54 g mag ox can raise fat test 0.145 percentage points. 4. Low hay consumption. Hay will stimulate saliva production, increase chewing and ruminating time, and reduce total ration moisture. A diet of medium quality hay will result in 27.1 L of saliva per kilogram of dry matter. 14 5. Haylage chopped too short. This will reduce total chewing time, increase rate of passage, and lower fiber digestion in the rumen. Alfalfa silage diets resulted in 14.3 L of saliva per kilogram of dry matter. 14 6. High concentrate intake. Concentrate replaces forage in the diet and, thus, fiber levels are reduced. Maryland workers 14 summarized data from cows fed a diet containing 30% forage. These cows produced 199 g less sodium bicarbonate equivalent (in saliva) than cows fed a diet with 70% forage. 7. Large concentrate meals. Concentrate feeding patterns (over 3 kg per meal) can result in "slug" fermentation patterns, which lower rumen pH and increase the total time during which rumen pH remains below 6. 8. Small concentrate particle size. Concentrate form is important because small particle size results in a rapid digestion of fermentable carbohydrate and alters the rate of feed passage in the rumen. 9. High-moisture grain. Grain moisture will affect solubilization of carbohydrate and nitrogen fractions and depress intake, especially at higher moisture levels (over 30% moisture). 10. High concentrations of soluble or fermentable carbohydrate. This affects the amount and rate of rumen carbohydrate degradation, fiber digestion, rumen pH, and VFA patterns. 11. Low fat test. Fat test variation of individual cows may be a problem concealed by a normal herd average test. If protein percentages exceed fat percentages by 0.4 units or Holstein cows test below 2.5% milk fat, abnormal rumen VFA and pH patterns can be expected. 30 12. Heat stress. A combination of heat, humidity, radiation, and air move-
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FEED ADDITIVES
ment can depress dry matter intake, shift feed consumption patterns, and affect blood mineral balance, which can be corrected with a buffer. 13. Low dry matter intake. Feed intake should be monitored at all times. A decline of 1 kg could be related to several other factors that a buffer could correct. Economic Responses Pennsylvania researchers 7 summarized 18 research reports in which cows received 0.75% sodium bicarbonate in the ration dry matter. Using applied neoclassical statistics and this data, they determined the cost to dairy managers of making the wrong decision. A type one error is using sodium bicarbonate in situations where it will not give a response. A type two error is not using sodium bicarbonate when it will give a response. With milk valued at $0.28fkg and feed priced at $0.15/kg, a type one error costs $0.04 per cow per day and a type two error costs $0.30 per cow per day. A summary of24 research studies from 1975 through 1985 involving 2087 cows found an increase of 1 kg of 3.5% milk fat in buffer-treated cows compared with control animals. 13 The economic response was $2.30 for each dollar invested in sodium bicarbonate. The average intake was 150 g of sodium bicarbonate per day (1.43% of the grain mixture). A telephone market survey13 of 500 dairy producers reported fat tests increased (61 %) and milk yield increased (6%) when sodium bicarbonate was fed. Of the dairy farmers using buffers, 95% were satisfied with results and 78% were continuous users. Another study,30 which involved 2684 DRI dairy farmers in nine midwest states, found 54.5% used buffers and cows produced 571 kg more milk per cow annually compared with herds not feeding buffers. NIACIN Niacin (B3) is a generic term for nicotinic acid, nicotinamide, and other compounds that have similar biologic activity. The major biologic function of niacin is its role in the coenzyme system NAD+/NADP+. Over 40 biologic reactions involve the transfer of hydrogen via this coenzyme system in carbohydrate, lipid, and protein metabolism, ATP formulation, and enzyme regulation. Dietary niacin sources are variable, with low biologic availabilities, especially in nonruminants. 31 Rumen microbes can synthesize niacin, but this source could be limited in early lactation due to ration ingredient changes postpartum and rumen environmental shifts (higher concentrate levels with lower rumen pH values). Milk Production Results A number of research studies have been conducted to determine the effe6t of niacin supplementation on milk yield and composition (Table 6). The current Table 6. Production Response to Supplemental Niacin INCREASE OVER CONmOLS
NUMBER OF DIETS
Normal Added fat
STUDIES
Milk
Milk Fat
Milk Protein
19 5
(kg) +0.76 -0.36
(%) +0.156 -0.044
(%) +0.06 +0.10
From Hutjens MF: Niacin in dairy cattle. NFIA Nutrition Institute Proceedings, 1990; with permission.
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MICHAEL FRANCIS HUT]ENS
recommended level is 6 g per cow fed 2 weeks prepartum and continued to peak dry matter intake (80 to 120 days postpartum). European researchers13 have successful used 3 g per cow while field recommendations approach 10 to 12 g per day. Kansas data44 indicated milk yield improvement when niacin was increased from 3 to 6 g, but not at 12 g per head per day. New Hampshire researchers 46 summarized several research results with niacin and reported a benefit to cost ratio of 6: 1 ($0.39 return in milk yield for an investment of $0.06 per cow for 6 g per day). California35 and Illinois 17 researchers have also reported favorable economic responses with supplemental niacin (over $0.11 greater income over feed costs per cow per day). Mode of Action With Niacin Improved energy balance in early lactation has been reported. Body fat mobilization was reduced, lowering free fatty acids, lowering beta-hydroxybutyric acid (ketone body), and maintaining higher blood glucose levels. Reduced cyclic adenosine monophosphate has been reported in human and rat studies. Illinois data33 indicated favorable blood metabolite concentrations in cows fed niacin in early lactation (2 to 5 weeks postpartum). Schwab 46 reported significant reductions in subclinical and clinical ketosis. German, Wisconsin, and Illinois data19,22,32,45 support this mode of action as niacin appeared to "normalize" weight loss. Increased dry matter intake (0.8 kg per cow) has been reported by Kansas researchers 44 with added niacin in soybean meal (natural protein) based diets. An increase of 1 kg of dry matter can support 2 kg of higher milk yield or minimize weight loss by improving the cow's energy status. The higher dry matter - intake response could be related to reduced subclinical ketosis. Indiana50 and Kansas researchers 44 suggested that niacin had an effect on rumen fermentation, increasing synthesis of microbial protein and reducing rumen concentration of urea nitrogen. Wisconsin 1 workers found no microbial growth response to niacin in three experiments in controlled in vitro incubations, suggesting sufficient endogenous niacin was present to support microbial growth. Horner 26 reported niacin increased microbial protein synthesis (especially protozoal protein) and enhanced propionate production (improved glucose balance and reduced ketosis risk). Illinois workers 17 also reported increased numbers of entodiniomorph protozoa populations in rumen contents in cattle fed niacin. While the role of niacin in improving microbial growth is controversial, data suggest niacin should be fed (not injected) to gain potential rumen responses. Improvements in milk protein yield associated with niacin feeding are summarized in Table 6. Niacin-supplemented COWS 17,27,31 had higher milk protein concentrations, which were associated with reversal of the milk-protein depressing effects of fat feeding (cottonseed, soybeans, or calcium salts of fatty acids). Possible explanations for niacin's beneficial effect on milk protein concentrations in fat-supplemented diets include greater microbial synthesis of protein (depressed by fat feeding) or increased plasma glucose and insulin due to niacin supplementation. If insulin plays a role in mammary casein synthesis, niacin's effect of increasing plasma insulin might contribute to increases in milk protein. Plasma tryptophan (an amino acid and niacin precursor) was higher in cows fed niacin. Availability of tryptophan could be limiting for milk protein synthesis if large amounts of tryptophan are required to meet the cow's niacin requirements. Wisconsin workers 51 also reported beneficial responses in milk protein to supplemental niacin, especially in fat-supplemented rations.
533
FEED ADDITIVES
Field Applications With Niacin Supplementation After reviewing niacin research results and observing field responses, the following points should be considered by dairy producers and veterinarians. 30 1. Target animals that may respond economically include high-producing herds (over 8181 kg per cow) and cows (over 9091 kg), cows in negative energy balance, ketosis-prone cows, heavy dry cows, and cows experiencing low dry matter intake in early lactation. These target animals are in negative energy balance and may respond to niacin with improved lipid metabolism. 2. Heavier dry cows. Those with body condition scores of 3, 4, and 5 have optimal response. Illinois 32 and New Hampshire 46 data indicate thin cows are less responsive (cow numbers in these studies are limited). Under field conditions, separating close-up dry cows by body condition for niacin supplementation is not practical. Niacin can be fed to all cows if an adequate percent of target animals exist in the herd. 3. To maintain higher blood niacin levels at parturition and to minimize fatty liver formation, niacin should be supplemented 1 to 2 weeks prepartum to 10 to 12 weeks postpartum. Blood and milk data33 indicate significant responses in early lactation (2 to 6 weeks postpartum). 4. Both forms of niacin (nicotinic acid and nicotinamide) are biologically effective in dairy cattle. 33 5. Added fat (cottonseed, soybeans, and protected fat) can depress milk protein test by 0.1 to 0.2 percentage points. 31 Milk protein recovery responses with added niacin and fat are variable and should be evaluated on a farm-byfarm basis. 6. Levels of 6 to 8 g of added niacin appear adequate. Higher levels should be evaluated on a cost versus response basis. 7. Niacin can be added to a ruminant-stress pack along with buffers, trace minerals, vitamins, and antibiotics. Nocek41 reported a significant increase in milk yield (1.2 kg per cow in the first 90 days postpartum), higher income over feed costs, a decrease in cystic ovaries, and fewer days to first heat with a stress pack containing niacin. Niacin is not palatable and should be incorporated with a palatable carrier (such as distillers grain or molasses) at a rate of 6 g of niacin with 115 g or more of the carrier feed.
ANIONIC SALTS Anionic salts (ammonium chloride, ammonium sulfate, aluminum sulfate, magnesium sulfate, or calcium chloride) cause rations to be more acidic, increasing absorption of dietary calcium and stimulating mobilization of bone calcium. 42 When more blood calcium is available, the cow is able to maintain blood calcium levels when the calcium drain due to milk synthesis occurs. Canadian workers6 reported 48% milk fever when cationic (control) diets were fed and no milk fever with anionic diets. Colorado researchers 42 reported a 13% decrease (from 17 to 4%) when cows received anionic salts with calcium intakes as high as 150 g per day. Feeding 100 g ammonium chloride and 100 g magnesium sulfate for 2 to 3 weeks prepartum has resulted in favorable responses in the field (reduced milk fever and hypocalemia, less retained placenta, and higher dry matter intake postpartum). Anionic salts are unpalatable, should be mixed with 200 to 454 g of a palatable carrier (such as distillers grain, molasses, or heated soybeans), and be pelleted to avoid separation.
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MICHAEL FRANCIS HUT}ENS
Additional research is needed to determine optimal combinations of anionic salts, levels, and duration of feeding. ASPERGILLUS ORYZAE
Aspergillus oryzae (AO) is a fermentation extract produced from a selected strain of enzyme-producing AO and is marketed under the tradename Amaferm (Bioenzyme Enterprises, Inc., St. Joseph, MO). The fungal additive has its main effect in the rumen, increasing cellulolytic bacteria, shifting VFA fermentation patterns, and stabilizing ruminal pH. Milk yield responses summarized from seven research studies were 28.5 kg for AO-supplemented animals compared with 27.3 kg for control cows (Hallada CM, personal communication, 1990). Arizona researchers 54 reported animals in hot environmental conditions had reduced body temperatures when AO was fed. Additional research is needed to evaluate which type of diet will have optimal economic responses and its role with other rumen additives (such as yeast and buffers). BACTERIAL DIRECT-FED MICROBIALS Bacterial direct-fed microbials (BDFM) or probiotics are microorganisms that have been selected for their ability to assist in maintaining a bacterial balance in the host animal's digestive tract during stressful or disease situations (Hallada CM, personal communication, 1990). Methods BDFM bacteria use to "balance" microHora are complex and unclear, but the following points should be considered. • Production of organic acids, hydrogen peroxide, and/or antibiotics could destroy undesirable microbes. • Lowering the oxidation/reduction potential could limit oxygen availability to pathogens. • The production of beneficial enzymes could improve nutrient availability. • Detoxification of harmful metabolites could improve animal health. Selected BDFM should be able to grow rapidly, colonize in the digestive tract, survive low stomach pH, remain viable during storage, and be compatible with specified antibiotic therapy. General groups of BDFM approved by the FDA include bacillus, bifidobacterium, streptococcus, bactereoeles, lactobacillus, pediococcus, and several other bacterial groups (Hallada CM, personal communication, 1990). Several forms of BDFM are available, including powders (for feed or liquid incorporation), boluses, pastes, and liquids. Additional research to determine optimal combinations, efficiency, target animals, number of colony-forming units per animal or unit of body weight, and economic response are needed before BDFM recommendations can be warranted. BETA-CAROTENE Beta-carotene is a biologic precursor of vitamin A, occurring naturally in feedstuffs (such as alfalfa and corn). Significant loss of beta-carotene occurs during storage of feedstuffs. The NRC (National Research Council) established a beta-carotene requirement of 19 mg of carotene per 100 kg liveweight per
535
FEED ADDITIVES
day.40 However, its additive role is through reproductive improvement and mastitis reduction. One specific role of beta-carotene is regulating host defense in blood lymphocytes through a receptor-binding protein mechanism. 9 Adding 300 mg of beta-carotene reduced milk somatic cell counts compared to unsupplemented coWS. IO ,43 The ability of blood neutrophils to phagocytize and kill bacteria was enhanced in beta-carotene - supplemented cOWS. 9 ,11 Early European research with beta-carotene supplementation improved reproductive performance, with fewer services per conception, fewer days open, and high blood progesterone. 4 However, recent studies have reported no improvement in reproductive performance, blood hormonal levels, or somatic cell counts. 2,5,38 Grave-Hoagland et a1 20 reported that beta-carotene is related to bovine luteal function in vitro during the winter when plasma beta-carotene levels were lower, but that no response occurred in the summer. Folman et al l8 reported that high carotene intake may have adverse effects on dairy cow fertility. Cows fed 500 mg carotene prepartum and 700 mg postpartum had a conception rate (all inseminations) of 27.9% compared to controls of 53.9%, with older cows (fourth and later lactation cows) more adversely affected. The response to beta-carotene is varied, with the immune response and mastitis control requiring further research effort. Beta-carotene is not recommended to improve reproduction when cows receive traditional feedstuffs and supplemental vitamin A.
CHOLINE Choline is usually classified as a B vitamin, but does not fit in the traditional role of a vitamin. Its roles in dairy nutrition include minimizing fatty liver formation, improving neurotransmission, and serving as a methyl donor.I5 The lack of response to dietary choline is due to extensive rumen degradation, estimated to be 85 to 95% of supplemental choline. 16,47 Thus, dietary sources and supplementation are not benencial. 48 Erdman l5 summarized five studies from Wisconsin 21 and Maryland l5 when choline was postruminally infused (15 to 90 g per day). The average milk response to choline was + 1.0 kg per day, +0.17 percent, and + 1.5 kg per day for milk, fat percent, and fat-corrected milk, respectively. The primary mechanism of interest in dairy cows is choline's effect on triglyceride transfer from the liver, especially in early lactation when free fatty acids from adipose tissue are mobilized and formed into lipoproteins, requiring choline-containing phospholipids. Choline could also spare methionine, which otherwise would be used for choline synthesis (10 g of choline would provide the equivalent methyl groups found in 44 g of methionine). Diets low in methionine may be improved by adding 30 g of rumen-protected choline. Choline will be more difficult to protect in the rumen than amino acids because it is extremely hygroscopic. Additional research on protected choline and its direct and indirect roles is needed before it can be recommended.
IONOPHORES Monensin (common brand name is Rumensin [Elanco, Indianapolis, IN]) and lasalocid (common brand name is Bovatec [Hoffman-LaRoche Inc., Nutley, NJ]) are antibiotics that can change rumen fermentation patterns. The initial
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MICHAEL FRANCIS HUTJENS
research was conducted with beef cattle. In trials with monensin involving dairy animals, growth improvement ranged from 6 to 14% with no negative effects on reproduction, calving ease, or calf size. Pennsylvania data28 indicated heifers calved 38 days earlier due to improved growth and feed efficiency, resulting in a savings of $62.00. The cost of monensin was 1.2¢ per day or $5.00 per animal, resulting in a benefit to cost ratio of 12: 1. Lasalocid research has similar growth improvement and feed efficiency responses. Lasalocid can be fed to animals below 180 kg and is associated with fewer feed reduction problems when initially fed compared with monensin. Both lasalocid and monensin are labeled as coccidiostats. The modes of action for ionophores include a shifting of VFA and decreasing methane production in the rumen, improving growth and feed efficiency, sparing dietary protein, and changing rumen fill and rate of passage. The benefit of ionophores as coccidiostats is improved growth and health in young animals.
METHIONINE HYDROXY ANALOG Methionine is an essential sulfur-containing amino acid which can be involved in the formation of lipoproteins in the liver. McCarthy37 successfully injected methionine intravenously into cows suffering from ketosis, correcting the disorder. Methionine hydroxy analog (MHA) is chemically similar to methionine and was considered resistant to microbial degradation. However, Wisconsin workers 34 found 99% of MHA was degraded or altered in the rumen. Most of the published research36 with MHA has shown limited improvement in milk yield, but increased milk fat and fat-corrected milk. Minnesota workers 36 conducted three lactation studies in which milk-fat production was improved 10% with 25 to 30 g MHA. Similar results were obtained with 20 g methionine. Factors resulting in positive response to MHA include stage of lactation (first 100 days postpartum), level of milk production (over 23 kg milk), dosage (0.15% MHA of ration dry matter or 30 g), high concentrate diets (over 50%), and lower levels of dietary protein (less than 15%). The possible modes of action include lipoprotein synthesis, increased cellulose digestion, higher rumen protozoa counts, and increased acetate-to-propionate ratio. 36 Rumen responses could explain similar responses with MHA or methionine. Minnesota researchers 36 calculated a net profit of $0.19 per cow per day or $21.25 per cow (fed for 16 weeks postpartum, $0.10 for MHA per day, $13.00 per 45 kg of milk, and $0.17 fat-test differential). MHA can be found in commercial buffer and stress packs. The research with MHA has been variable, with cost a concern. YEAST CULTURE Yeast culture is a live culture of yeast (a fungi) and the media on which it was grown. It is dried so as to preserve the fermenting capacity of the yeast. Several other types of yeast products are available from fermentation processes (such as brewers and distillers yeast). A summary of seven yeast studies 29 concluded that cows fed yeast averaged 25.1 kg of 4% fat-corrected milk compared to control cows at 23.5 kg. However, results are variable and inconsistent. Early lactation cows had a significant increase in milk yield while midlactation cows had no response. 23 Milk composition (fat and protein levels)
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FEED ADDITIVES
response is also variable. Erdman and Sharman 16 reported no effect of yeast culture on milk fat percent, but a slight increase in milk protein content. The main effect of yeast culture is to stabilize the rumen environment. Concentrations of cellulolytic and anaerobic bacteria were higher in in vitro and in vivo systems. 29 Rumen pH has been elevated in some studies with yeast cultures, but pH changes are not consistent. A decrease in acetate-to-propionate ratio has also been observed, which would favor milk protein synthesis. A reduction in rumen lactic acid concentrations has been reported. 55 Higher dry matter intakes were reported by Florida23 and English workers,55 while other studies showed no difference. 55 Yeast cultures are being studied to determine mode of action, optimum level, and correct stage of lactation during which to feed. Early lactation (2 weeks prepartum to 8 weeks postpartum) appears to be the optimum time to feed yeast culture to stabilize the rumen environment as cows are shifted from dry cow to high-energy diets. 29 Various forms and concentrations of yeast culture products are commercially available.
ZINC METHIONINE Zinc methionine is a compound composed of zinc and methionine. The additive is resistant to degradation by rumen microbes. 24 Zinc methionine was absorbed to a similar extent compared to zinc oxide, but zinc methionine appears to be metabolized differently after absorption with lower urinary excretion and slower rate of decline in plasma zinc. 52 In eight lactation studies in Washington, Colorado, Britain, Illinois, New York, and Arkansas, somatic cell counts averaged 320,000 and 217,000, and milk yield was 30.3 kg and 31.8 kg for control and zinc-supplemented cows, respectively (Schugal LM, personal communication, 1988). However, Ohio researchers found zinc methionine supplementation did not have an effect on wound healing, mastitis, immune response, or plasma zinc levels. 25 Zinc methionine has been reported in the field to harden hoof surfaces and reduce foot disorders. Several concentrations of zinc methionine are commercially available (feed labels must be checked to avoid excessive consumption). The product can be fed under field conditions when a response can be expected, but the effects should be monitored. CONCLUSION Interest in feed additives will continue. Isoacids (a group of short-chain and branch-chain VFA needed by fiber-digesting bacteria) are examples of an additive that was used in the early 1980s, but whose use has since declined because of cost, handling limitations, and research indicating alternative sources of isoacids are synthesized from protein. New additives will appear that can improve milk and growth performance. Table 7 summarizes dairy additives, their level of inclusion, cost per animal per day, and field status ("recommended" refers to additive inclusion as needed, "experimental" indicates additional research and study are warranted, "evaluative" suggests use with careful monitoring in specific situations, and "not recommended" reflects a lack of economic response or research from which to recommend current use.) The status of these additives will change as additional research and field experiences occur.
538
MICHAEL FRANCIS HUTJENS
Table 7. Guidelines and Considerations for Dairy Feed Additives COST ADDITIVE
Anionic salts Aspergillus oryzae Bentonite Beta carotene Buffers Sodium bicarbonate Sodium sesquicarbonate Magnesium oxide Choline Ionophore Isoacids Methionine hydroxy analog Niacin Probiotics (BDFM) Yeast culture Zinc methionine
LEVEL
($/DAY)
STATUS
200 g 3g 454-600 g 200-300 mg
0.18 0.05 0.06 0.30
Experimental Experimental Evaluative Not recommended
110-225g 160-340 g 50-90 g 30 g
0.06 0.05 0.02 0.10
Recommended Recommended Recommended Not recommended
0.02 0.20 0.10
Recommended Not recommended Not recommended
50-200 mg 90 g 30 g 6-12 g Varies 10-120 g 5g
0.06-0.12 0.03-0.18 0.06 0.02
Recommended Experimental Evaluative Evaluative
REFERENCES 1. Abdouli H, Schaefer DM: Impact of niacin and length of incubation on protein synthesis, soluble to total protein ratio, and fermentation activity of ruminal microorganisms. J Anim Sci 62:244, 1986 2. Akordor FY, Stone JB, Walton JS, et al: Reproductive performance of lactating Holstein cows fed supplemental beta carotene. J Dairy Sci 69:2173, 1986 3. Armentano LE, Solorzano LC: Buffers for dairy cattle: Mechanisms of action as a basis for formulating buffer mixtures. Nutri News 1:2, 1989 4. Bindas EM, Gwazdauskas FC, Aiello RJ, et al: Reproductive and metabolic characteristics of dairy cattle supplemented with beta carotene. J Dairy Sci 67:1294, 1984 5. Bindas EM, Gwazdauskas FC, McGilliard ML, et al: Progesterone response to human chorionic gonadotropin in dairy cattle supplemented with beta carotene. J Dairy Sci 67:2978, 1984 6. Block E: Manipulating dietary anion and cation for prepartum dairy cows to reduce incidences of milk fever. J Dairy Sci 67:2939, 1984 7. Chalupa W, Ferguson JD, Galligan DT: Feeding the high producing cow. In Am Soc Agric Engineers Proceedings, Harrisburg, 1990, p 14 8. Chase LE: Yeast in dairy cattle feeding program. In Proceedings of the Cornell Nutrition Conference, Syracuse, NY, 1989, P 121 9. Chew BP: Beta carotene and vitamin A nutrition on animal health. In NFIA Nutrition Institute Proceedings, Kansas City, MO, 1990 10. Chew BP, Johnson LA: Effect of supplemental vitamin A and beta carotene on mastitis in dairy cows. J Dairy Sci 68(Suppl 1):191, 1985 11. Dahlquist SP, Chew BP: Effects of vitamin A and beta carotene on mastitis in dairy cows during the early dry period. J Dairy Sci 68(Suppl 1):191, 1985 12. Davis CL: The use of buffers in the ration of lactating dairy cows. In Regulation of Acid-Base Balance. Piscataway, NJ, Church and Dwight, 1979, p 51 13. Downer JV, Cummings KR: A 10 year review of lactation studies. J Dairy Sci 70(Suppl 1):198, 1987 14. Erdman RA: Dietary buffering requirements of the lactating dairy cow. J Dairy Sci 71:3246, 1988 15. Erdman RA: Choline nutrition in dairy cattle. In NFIA Nutrition Institute Proceedings, Kansas City, MO, 1990, P 1 16. Erdman RA, Sharman BK: Effect of yeast culture and sodium bicarbonate on milk yield and composition in dairy cows. J Dairy Sci 72:1929, 1989
FEED ADDITIVES
539
17. Erickson PS: Niacin-lipid interactions in dairy cows (Doctorate Thesis). University of Illinois, Urbana, IL, 1989 18. Folman Y, Ascarelli I, Kraus D, et al: Adverse effects of beta carotene in diet on fertility of dairy cows. J Dairy Sci 70:357, 1987 19. Fronk TJ, Schultz LH: Oral nicotinic acid as a treatment for ketosis. J Dairy Sci 62: 1804, 1979 20. Grave-Hoagland RL, Hoagland TA, Woody CO: Effect of beta carotene and vitamin A on progesterone production by bovine luteal cells. J Dairy Sci 71: 1 058, 1988 21. Grummer RR, Armentano LE, Marcus MS: Lactation response to short-term abomasal infusion of choline, inositol, and soy lecithin. J Dairy Sci 70:2518, 1987 22. Harmeyer J, Grabe CV: The effect of niacin supplement on ketogenesis on the dairy cow. Deutsche Tierarztliche Wochenschrift 88:401, 1986 23. Harris B Jr, Lobo R: Feeding yeast culture to lactating dairy cows. J Dairy Sci 71(Suppl 1):276, 1988 24. Heinrichs AJ, Conrad HR: Rumen solubility and breakdown of metal protein compounds. J Dairy Sci 66 (Suppl 1):47, 1983 25. Heinrichs AJ, Todhunter DA, Murray FA, et al: Zinc-methionine supplementation for dairy cows - a study of effects on plasma zinc, wound healing, mammary health, and immune responses. Ohio State Research Circular 281, 1984 26. Horner JL, Coppock CE, Moya JR, et al: Effect of niacin and whole cottonseed on ruminal fermentation, protein degradability, and nutrient digestibility. J Dairy Sci 71:1239, 1988 27. Horner JL, Coppock CE, Schelling GT, et al: Influence of niacin and whole cottonseed on intake, milk yield and composition, and systemic responses of dairy cows. J Dairy Sci 69:3087, 1986 28. Hutjens MF: Apply the 4 R's to feed additives. Dairy Herd Management, November, 1988 29. Hutjens MF: Feeding the high producing dairy cow: A role for natural additives. In Biotechnology in the Feed Industry. Alltech Technical 4th Proc, Lexington, KY, 1988, p 37 30. Hutjens MF: Applications of rumen buffers and buffer packs in dairy nutrition. In Application of Nutrition in Dairy Practice. Wayne, NJ, American Cyanamid, 1988, p 44 31. Hutjens MF: Niacin in dairy cattle. In NFIA Nutrition Institute Proceedings, Kansas City, MO, 1990 32. Jaster EH, Hartnell GF, Hutjens MF: Effect of feed supplemental niacin on milk production in six dairy herds. J Dairy Sci 66:1046, 1983 33. Jaster EH: Nicotinic acid or nicotinamide for lactating dairy cows. In Proceedings of the Degussa Technical Symposium, Atlanta, GA, 1988, p 3 34. Jones BA, Mohamed OE, Prange RW, et al: Degradations of methionine hydroxy analog in the rumen of lactating cows. J Dairy Sci 71:525, 1988 35. Kutches AJ: The influence of niacin supplementation on milk and fat production in early lactation. Special report. Lonza, Inc, Fair Lawn, NJ, 1983 36. Lundquist RG, Bhargara PK, Linn JG, et al: Methionine hydroxy analog for lactating dairy cattle. In Proceedings of the Minnesota Nutrition Conference, Minneapolis, MN 1982, P 31 37. McCarthy RD, Potter GA, Griel LC: Bovine ketosis and depressed fat test in milk: A problem of methionine metabolism and serum lipoprotein aberration. J Dairy Sci 51:459, 1968 38. Marcek JM, Appell LH, Hoffman CC, et al: Effect of supplemental beta carotene on incidence and responsiveness of ovarian cysts to hormone treatment. J Dairy Sci 68:71,1985 39. Ndwiga CA, Erdman RA, Vandersal JH, et al: Effect of type and site of acid neutralization on voluntary intake of corn silage by dairy heifers. J Dairy Sci 73:1561, 1990 40. National Research Council Committee: Nutrient Requirements of Dairy Cattle, ed 6. National Academy of Sciences, Washington, DC, 1989, p 43 41. Nocek]E, Vanderslice OL, English JE, et al: Evaluation of a nutritional supplement for dairy cows in early lactation. J Dairy Sci 66(suppl1):D16, 1986 42. Oetzel GR, Olson JD, Curtis CR, et al: Ammonium chloride and ammonium sulfate for prevention of parturient paresis in dairy cows. J Dairy Sci 71 :3302, 1988
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MICHAEL FRANCIS HUT]ENS
43. Rakes AH, Owens MR, Britt JH, et al: Effects of adding beta carotene to rations of lactating cows consuming different forages. J Dairy Sci 68:1732, 1985 44. Riddell DO, Bartley EE, Dayton AD, et al: Effect of nicotinic acid on microbial protein synthesis in vitro and on dairy cattle growth and milk production. J Dairy Sci 64:782, 1981 45. Schultz LH: Niacin in dairy rations. In Pacific N.W. Nutrition Conference Proceedings, Corvallis, OR, 1983 46. Schwab CG: Supplemental niacin for lactating dairy cows. In Proceedings of the 24th Annual New England Dairy Feed Conference, Concord, NH, 1983 47. Sharma BK, Erdman RA: Effects of dietary and abomasally infused choline on milk production responses of lactating dairy cows. J Nutr 119:248, 1989 48. Sharma BK, Erdman RA: In vitro degradation of choline from selected feedstuffs and choline supplements. J Dairy Sci 72:2772, 1984 49. Shaver RD, Erdman RA, Vandersal JH, et al: Effects of silage pH on voluntary intake of corn silage. J Dairy Sci 67:2045, 1984 50. Shields DR, Schaefer DM, Perry TW: Influence of niacin supplementation and nitrogen source on rumen microbial fermentation. J Anim Sci 57:1576, 1983 51. Skaar TC, Grummer RR, Dentine MR, et al: Seasonal effects on prepartum and postpartum fat and niacin feeding on lactation performance and lipid metabolism. J Dairy Sci 72:2028, 1989 52. Spears JW: Zinc methionine for ruminants: relative bioavailability of zinc in lambs and effects on growth and performance of growing heifers. J Anim Sci 67:835, 1989 53. Staples CR, Lough DS: Efficacy of supplemental dietary buffers for lactation cows. In Florida Nutrition Conference Proceedings, Gainesville, FL, 1987 54. Wallentine MV, Johnston NP, Andus D, et al: The effect of feeding Aspergillus oryzae culture-vitamin mix on the performance of lactating dairy cows during periods of heat stress. J Dairy Sci 69(Suppl 1}:189, 1986 55. Williams PEV: The mode of action of yeast culture in ruminant diets: A review of the effect on rumen fermentation patterns. In Biotechnology in the Feed Industry. Alltech Technical 5th Proceedings, Lexington, KY, 1989, p 65 Address reprint requests to Michael Francis Hutjens, BS, MS, PhD University of Illinois 315 Animal Sciences Laboratory 1207 West Gregory Drive Urbana, IL 61801
0749-0720/91 $0.00
+ .20
Feed Additives
Michael Francis Hutjens, BS, MS, PhD*
A feed additive can be defined as a feed ingredient or group of feed compounds that produces a desirable animal response in a nonnutrient role (such as a protein, mineral, or vitamin). Some feed additives may contain nutrients (such as sodium in sodium bicarbonate or methionine in zinc methionine) . Feed additives have gained attention and use due to higher milk yields, emphasis on milk components (especially milk protein), greater stress on milk cows, new research results, and extensive advertising by manufacturers. A 1983 field survey (Richetts R, personal communication, 1987) of additives used in herds producing over 9090 kg of milk found buffers, yeast, beta-carotene, niacin, methionine, and no additives were used on 62,17,16,3 and 10% of the farms, respectively. A 1987 survey of New York DHI (Dairy Herd Improvement) herds is summarized in Table 1 (Chase LE, personal communication). Feed additives are not a must or guarantee for higher milk yield or improved herd health. I
EVALUATING FEED ADDITIVES One method for evaluating a feed additive is to determine whether it satisfies four key factors: response, returns, research, and results. 28 Response refers to expected or performance changes the user could expect when a feed additive is included. • • • • • • • • •
Increase milk yield (peak milk and/or milk persistency) Increase in milk components (protein and/or fat) Increase dry matter intake Maintain a desirable rumen pH Stimulate rumen microbial synthesis of protein and/or volatile fatty acid (VFA) production Increase rate of passage or How of nutrients out of the rumen Improve fiber digestion in the rumen Stabilize rumen environment Improve growth (gain and/or feed efficiency conversion)
*Professor of Animal Sciences and Extension Dairy Specialist, Department of Animal Sciences, University of Illinois College of Agriculture, Urbana, Illinois Veterinary Clinics o/North America: Food Animal Practice-Vol. 7, No.2, July 1991
525
I!!!!
526
MICHAEL FRANCIS HUTJENS
Table 1. Use o/Feed Additives in 5700 Herds Whose Records are Processed at the New York DHI Computing Facility CURRENTLY
DISCONTINUED
USING
USING
PRODUCT
(%)
(%)
Buffers Ionophores Yeast Niacin Isoacids
67.6 35.4 17.2 14.4 13.0
23 8 49 30 62
• Minimize weight loss • Reduce heat stress effects • Improve health (such as less ketosis, reduced acidosis, or improved immune response) The veterinarian, consultant, nutritionist, or dairy manager should determine which responses to expect before adding the additive. Returns reflect the profitability of using a selected additive. If milk improvement is the measurable response, Table 2 can be used to determine break-even points. For example, a veterinarian recommends an additive that raises feed costs $0.10 per day. If milk is valued at $0.12 per 0.45 kg, every cow must produce 0.4 kg more milk to cover the added cost associated with the additive. Another consideration is if all cows receive the additive, but only those cows fresh fewer than 100 days respond. These responding cows must cover the additive costs for all cows (responsive and nonresponsive cows). For some responses (such as improved health or reduced stress) it is difficult to determine an objective economic value or an economic value that will be returned in the next lactation. One guideline is that an additive should return two dollars or more for each dollar invested in the additive; this covers nonresponsive cows and field conditions that could minimize the anticipated response. Other dairy managers feel the economic response to an additive must only cover the cost of the additive to be justified. Research is essential to determine whether experimentally measured responses can be expected in the field. Studies should be conducted under controlled and unbiased conditions, have statistically analyzed results (to determine whether the differences are reproducible), and be conducted under experimental designs that are similar to field situations (feed ingredients, feed delivery systems, level of milk yields, and various stages of lactation).
Table 2. Break-even Milk-yield Responses to Cover Additive Cost MILK PRICE
Additive Cost ($/cow/day)
10
0.02 0.06 0.10 0.30
0.1 0.3 0.5 1.4
($/45
ICG)
12 14 Milk increase needed (kg/day)
0.1 0.2 0.4 1.1
0.1 0.2 0.3 1.0
527
FEED ADDITIVES
Results obtained on individual farms are the economic payoff. Dairy managers and veterinarians must have a data base to compare and measure responses. Several tools to measure results include DHI milk records (peak milk, persistency, milk components, and milk curves), reproduction summaries, somatic cell count data, dry matter intake, heifer growth charts, and herd health profiles that will allow critical evaluation of a selected additive. The remainder of this article discusses feed additives applying the four key factors. Veterinarians should be able to objectively decide when and how to select and use various products. BUFFERS The ruminant animal has a complex acid-base regulating system, with the rumen varying in pH from 5.5 to 7. Rumen pH has been directly related to rumen VFA concentrations, a function of rumen microbial degradation of organic matter, water flux across the rumen, rumen flow rates, saliva flow, and feed acidity. If rumen pH is not optimal, dry matter intake will decrease, acidosis can cause health problems, and microbial yield of protein and energy decreases. The addition of dietary buffers to control rumen pH can be justified if bunk management and nutritional factors cause low pH. Successful applications 14 Qf buffers result in higher feed intake, increased milk yield, and favorable milk composition (Table 3). Evaluating Buffer Compounds Buffers are widely used in dairy feeding programs. Chemically, buffers are a combination of a weak acid and its salt. Such combinations resist changes in pH or hydrogen ion concentration. To function properly, the buffer must be water soluble (calcium carbonate is not) and its equivalence point (pKa) must be near the physiologic pH of the rumen. Sodium bicarbonate is a true buffer, with a pKa of 6.25. Other compounds, called alkalinizing or neutralizing agents, increase the pH of the rumen fluid; one example is magnesium oxide. Several commonly used products are discussed and summarized in Table 4. 14,53 Sodium bicarbonate (bicarb) is a white crystalline compound derived from soda ash. It is 99% sodium bicarbonate (NaHC0 3 ) and GRAS listed (generally recognized as safe). The pH of a 1 % solution is 8.4 and it buffers at a pH of 6.2. Soda ash is produced from trona mineral. Bicarb is widely used as a buffer and has been thoroughly researched. Research has shown it to increase rumen pH and osmolarity, produce a more desirable rumen fermentation, and increase rumen fluid outflow. Sodium sesquicarbonate is a relatively new product sold under the trade name S-Carb (FMC Agricultural Chemical Group, Philadelphia, PA). It contains a mixture of sodium bicarbonate and sodium carbonate (an alkalinizing agent). The pH of a 1% solution is 9.9. It is a white, needlelike crystal product and GRAS listed. Six published experiments with sodium sesquicarbonate reported an increase of 1.6 kg milk and 0.23% milk fat compared to control COWS. 53 The price of sodium sesquicarbonate is typically lower than sodium bicarbonate. Alkaten (Church and Dwight Co., Inc., Princeton, NJ) is sodium sesquicarbonate, but contains about 6% inert materials, is slightly lower in sodium, and is not as refined. Trona also is sodium sesquicarbonate, but contains 10% inert material (dolomitic marlstone, shale, shortite, mudstone, and other products). Research work on trona has been limited. The presence of substantial amounts of foreign material in trona should be monitored in future experiments.
~
c:J1
00
+0.1 -1.1
+0.3 +0.6
3 6 11 9
+0.2 +0.2 +0.6 -0.1 0 +0.3
55 14 17 8 3 8
(NUMBER)
From Erdman RA: Dietary buffering requirements of the lactating dairy cow.
Magnesium oxide Adequate forage Low forage
Potassium carbonate Potassium bicarbonate
Sodium bicarbonate Adequate forage Low forage Corn silage Alfalfa hay Alfalfa/grass silage Alfalfa silage & corn silage
COMPOUNDS
STUDIES
Milk Yield (kg)
+0.05 +0.15
+0.16 +0.95
-0.01 +0.04 -0.02 -0.06
+0.05 +0.22 +0.07 -0.07 +0.04 NA
(units)
pH
Rumen
-0.04 +0.06 -0.02 NA +0.01 +0.04
Milk Protein (%)
CHANGES FROM CONTROLS
J Dairy Sci 71:3246, 1988; with permission.
+0.16 +0.35
+0.40 +0.45
+0.1 +0.28 +0.16 +0.03 -0.03 +0.10
Fat Test (%)
Table 3. Production Comparisons of Various Compounds from Published Research Studies with Different Forage Sources
-0.1 -1.8
+1.3 -0.1
+0.2 -0.1 +0.5 -0.1 +0.2 +0.2
Dry Matter (kg)
529
FEED ADDITIVES
Table 4. Composition and Characteristics of Buffers and Alkalinizing Agents for Ruminant Animals ITEM NaHC03 (%) N~C03 (%)
NAHC03
S-CARB
ALKATEN
TRONA
100.0
37.0 47.0
34.8 43.8
33.6 42.2
16.0 30.4
14.9 6.1 28.5
14.0 10.0 26.0
6.25
6.25 10.25
6.25 10.25
6.25 10.25
7
13
13
13
Source dependent
12
13
13
11
50
Water of hydration (%) Inert material (%) Sodium (%) Magnesium (%) pKa Solubility (g/100 mL) Acid-consuming (mEqJkg)
27.4
MGO
54 None
From Erdman RA: Dietary buffering requirements of the lactating dairy cow. J Dairy Sci 71:3246, 1988; Staples CR, Lough DS: Efficacy of supplemental dietary buffers for lactation cows. In Florida Nutrition Conference Proceedings, 1987; with permission.
Magnesium oxide (mag ox) is used as a source of magnesium (54%) and as an alkalinizing agent. Mag ox appears to regulate rumen fermentation and improve uptake of milk fat precursors by the mammary gland. 3 Solubility, heat treatment, and particle size can affect the action of mag ox. Calcium carbonate (limestone or CaC03 ) has little if any buffering action in the rumen. It can increase fecal pH when high starch diets are fed by increasing starch digestion in the small and large intestines and improving starch-splitting enzyme activity. Adding limestone to diets above 0.6 to 0.8% calcium has provided little beneficial effect. 12 Sodium bentonite, a clay mineral, is used as a pellet binder by the feed industry and is found in some buffer packs. It can prevent milk fat depression by shifting VFA patterns. It also swells in the rumen (5 to 20 times its size), adsorbs and exchanges minerals and ammonia, and may add bulk to the ration. Several other products are being used as buffers or in buffer packs. Potassium carbonate, potassium bicarbonate, magnesium carbonate, and sodium carbonate provide action similar to sodium bicarbonate. Potassium salts can be beneficial under heat stress and in low potassium diets, but are more expensive and less available commercially. The carbonate forms are alkalinizing agents and are generally unpalatable. Suggested levels of buffers and alkalinizers are listed in Table 5. Palatability of most buffers is low and requires careful management to avoid reduced feed intake. Buffer Use Strategies The key question in buffer usage is when dairy managers and nutritionists can expect an economically favorable response to buffers. The following is a list of conditions in which a positive response to buffers may be anticipated. 1. High corn silage diets. These are high in moisture (60 to 70%) and fermentable carbohydrate (over 30%) and low in pH (3.9 to 4.2). Optimal silage pH is 5.6 for maximum intake. 39,49 Corn silage has a shorter particle size
530
MICHAEL FRANCIS HUTJENS
Table 5. Feeding Recommendations of Commonly Used Products for Lactating Cows PRODUCT
Sodium bicarbonate Sodium sesquicarbonate Magnesium oxide Sodium bentonite Calcium carbonate Potassium carbonate
LEVEL (G/DAY)
110-225 160-340 50-90 450-900 115-180 270-410
From Hutjens MF: Applications of rumen buffers and buffer packs in dairy nutrition. In Applications of Nutrition in Dairy Practice. Wayne, NJ, American Cyanamid, 1988, p 44; with permission.
due to more precise chopping and requires less salivation due to its wet nature. Buffering capacity of corn silage from pH 4 to 9 is 476 mEqfkg dry matter compared with alfalfa hay at 822 mEqfkg and timothy hay at 511 mEqfkg dry matter.l4 2. Wet rations. Diets with over 50% moisture depress total dry matter intake 6 to 9% if the wet feed has been fermented. Water per se does not depress dry matter intake (as with pasture or green chop). 3. Lower fiber rations. Those below· 19% acid detergent fiber (ADF) depress rumination and lead to rumen acidosis. Maryland researchers 14 suggest that a 1% increase in ADF (above 14%) increases fat test 0.145 percentage points and 108 g of bicarb and 54 g mag ox can raise fat test 0.145 percentage points. 4. Low hay consumption. Hay will stimulate saliva production, increase chewing and ruminating time, and reduce total ration moisture. A diet of medium quality hay will result in 27.1 L of saliva per kilogram of dry matter. 14 5. Haylage chopped too short. This will reduce total chewing time, increase rate of passage, and lower fiber digestion in the rumen. Alfalfa silage diets resulted in 14.3 L of saliva per kilogram of dry matter. 14 6. High concentrate intake. Concentrate replaces forage in the diet and, thus, fiber levels are reduced. Maryland workers 14 summarized data from cows fed a diet containing 30% forage. These cows produced 199 g less sodium bicarbonate equivalent (in saliva) than cows fed a diet with 70% forage. 7. Large concentrate meals. Concentrate feeding patterns (over 3 kg per meal) can result in "slug" fermentation patterns, which lower rumen pH and increase the total time during which rumen pH remains below 6. 8. Small concentrate particle size. Concentrate form is important because small particle size results in a rapid digestion of fermentable carbohydrate and alters the rate of feed passage in the rumen. 9. High-moisture grain. Grain moisture will affect solubilization of carbohydrate and nitrogen fractions and depress intake, especially at higher moisture levels (over 30% moisture). 10. High concentrations of soluble or fermentable carbohydrate. This affects the amount and rate of rumen carbohydrate degradation, fiber digestion, rumen pH, and VFA patterns. 11. Low fat test. Fat test variation of individual cows may be a problem concealed by a normal herd average test. If protein percentages exceed fat percentages by 0.4 units or Holstein cows test below 2.5% milk fat, abnormal rumen VFA and pH patterns can be expected. 30 12. Heat stress. A combination of heat, humidity, radiation, and air move-
531
FEED ADDITIVES
ment can depress dry matter intake, shift feed consumption patterns, and affect blood mineral balance, which can be corrected with a buffer. 13. Low dry matter intake. Feed intake should be monitored at all times. A decline of 1 kg could be related to several other factors that a buffer could correct. Economic Responses Pennsylvania researchers 7 summarized 18 research reports in which cows received 0.75% sodium bicarbonate in the ration dry matter. Using applied neoclassical statistics and this data, they determined the cost to dairy managers of making the wrong decision. A type one error is using sodium bicarbonate in situations where it will not give a response. A type two error is not using sodium bicarbonate when it will give a response. With milk valued at $0.28fkg and feed priced at $0.15/kg, a type one error costs $0.04 per cow per day and a type two error costs $0.30 per cow per day. A summary of24 research studies from 1975 through 1985 involving 2087 cows found an increase of 1 kg of 3.5% milk fat in buffer-treated cows compared with control animals. 13 The economic response was $2.30 for each dollar invested in sodium bicarbonate. The average intake was 150 g of sodium bicarbonate per day (1.43% of the grain mixture). A telephone market survey13 of 500 dairy producers reported fat tests increased (61 %) and milk yield increased (6%) when sodium bicarbonate was fed. Of the dairy farmers using buffers, 95% were satisfied with results and 78% were continuous users. Another study,30 which involved 2684 DRI dairy farmers in nine midwest states, found 54.5% used buffers and cows produced 571 kg more milk per cow annually compared with herds not feeding buffers. NIACIN Niacin (B3) is a generic term for nicotinic acid, nicotinamide, and other compounds that have similar biologic activity. The major biologic function of niacin is its role in the coenzyme system NAD+/NADP+. Over 40 biologic reactions involve the transfer of hydrogen via this coenzyme system in carbohydrate, lipid, and protein metabolism, ATP formulation, and enzyme regulation. Dietary niacin sources are variable, with low biologic availabilities, especially in nonruminants. 31 Rumen microbes can synthesize niacin, but this source could be limited in early lactation due to ration ingredient changes postpartum and rumen environmental shifts (higher concentrate levels with lower rumen pH values). Milk Production Results A number of research studies have been conducted to determine the effe6t of niacin supplementation on milk yield and composition (Table 6). The current Table 6. Production Response to Supplemental Niacin INCREASE OVER CONmOLS
NUMBER OF DIETS
Normal Added fat
STUDIES
Milk
Milk Fat
Milk Protein
19 5
(kg) +0.76 -0.36
(%) +0.156 -0.044
(%) +0.06 +0.10
From Hutjens MF: Niacin in dairy cattle. NFIA Nutrition Institute Proceedings, 1990; with permission.
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MICHAEL FRANCIS HUT]ENS
recommended level is 6 g per cow fed 2 weeks prepartum and continued to peak dry matter intake (80 to 120 days postpartum). European researchers13 have successful used 3 g per cow while field recommendations approach 10 to 12 g per day. Kansas data44 indicated milk yield improvement when niacin was increased from 3 to 6 g, but not at 12 g per head per day. New Hampshire researchers 46 summarized several research results with niacin and reported a benefit to cost ratio of 6: 1 ($0.39 return in milk yield for an investment of $0.06 per cow for 6 g per day). California35 and Illinois 17 researchers have also reported favorable economic responses with supplemental niacin (over $0.11 greater income over feed costs per cow per day). Mode of Action With Niacin Improved energy balance in early lactation has been reported. Body fat mobilization was reduced, lowering free fatty acids, lowering beta-hydroxybutyric acid (ketone body), and maintaining higher blood glucose levels. Reduced cyclic adenosine monophosphate has been reported in human and rat studies. Illinois data33 indicated favorable blood metabolite concentrations in cows fed niacin in early lactation (2 to 5 weeks postpartum). Schwab 46 reported significant reductions in subclinical and clinical ketosis. German, Wisconsin, and Illinois data19,22,32,45 support this mode of action as niacin appeared to "normalize" weight loss. Increased dry matter intake (0.8 kg per cow) has been reported by Kansas researchers 44 with added niacin in soybean meal (natural protein) based diets. An increase of 1 kg of dry matter can support 2 kg of higher milk yield or minimize weight loss by improving the cow's energy status. The higher dry matter - intake response could be related to reduced subclinical ketosis. Indiana50 and Kansas researchers 44 suggested that niacin had an effect on rumen fermentation, increasing synthesis of microbial protein and reducing rumen concentration of urea nitrogen. Wisconsin 1 workers found no microbial growth response to niacin in three experiments in controlled in vitro incubations, suggesting sufficient endogenous niacin was present to support microbial growth. Horner 26 reported niacin increased microbial protein synthesis (especially protozoal protein) and enhanced propionate production (improved glucose balance and reduced ketosis risk). Illinois workers 17 also reported increased numbers of entodiniomorph protozoa populations in rumen contents in cattle fed niacin. While the role of niacin in improving microbial growth is controversial, data suggest niacin should be fed (not injected) to gain potential rumen responses. Improvements in milk protein yield associated with niacin feeding are summarized in Table 6. Niacin-supplemented COWS 17,27,31 had higher milk protein concentrations, which were associated with reversal of the milk-protein depressing effects of fat feeding (cottonseed, soybeans, or calcium salts of fatty acids). Possible explanations for niacin's beneficial effect on milk protein concentrations in fat-supplemented diets include greater microbial synthesis of protein (depressed by fat feeding) or increased plasma glucose and insulin due to niacin supplementation. If insulin plays a role in mammary casein synthesis, niacin's effect of increasing plasma insulin might contribute to increases in milk protein. Plasma tryptophan (an amino acid and niacin precursor) was higher in cows fed niacin. Availability of tryptophan could be limiting for milk protein synthesis if large amounts of tryptophan are required to meet the cow's niacin requirements. Wisconsin workers 51 also reported beneficial responses in milk protein to supplemental niacin, especially in fat-supplemented rations.
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Field Applications With Niacin Supplementation After reviewing niacin research results and observing field responses, the following points should be considered by dairy producers and veterinarians. 30 1. Target animals that may respond economically include high-producing herds (over 8181 kg per cow) and cows (over 9091 kg), cows in negative energy balance, ketosis-prone cows, heavy dry cows, and cows experiencing low dry matter intake in early lactation. These target animals are in negative energy balance and may respond to niacin with improved lipid metabolism. 2. Heavier dry cows. Those with body condition scores of 3, 4, and 5 have optimal response. Illinois 32 and New Hampshire 46 data indicate thin cows are less responsive (cow numbers in these studies are limited). Under field conditions, separating close-up dry cows by body condition for niacin supplementation is not practical. Niacin can be fed to all cows if an adequate percent of target animals exist in the herd. 3. To maintain higher blood niacin levels at parturition and to minimize fatty liver formation, niacin should be supplemented 1 to 2 weeks prepartum to 10 to 12 weeks postpartum. Blood and milk data33 indicate significant responses in early lactation (2 to 6 weeks postpartum). 4. Both forms of niacin (nicotinic acid and nicotinamide) are biologically effective in dairy cattle. 33 5. Added fat (cottonseed, soybeans, and protected fat) can depress milk protein test by 0.1 to 0.2 percentage points. 31 Milk protein recovery responses with added niacin and fat are variable and should be evaluated on a farm-byfarm basis. 6. Levels of 6 to 8 g of added niacin appear adequate. Higher levels should be evaluated on a cost versus response basis. 7. Niacin can be added to a ruminant-stress pack along with buffers, trace minerals, vitamins, and antibiotics. Nocek41 reported a significant increase in milk yield (1.2 kg per cow in the first 90 days postpartum), higher income over feed costs, a decrease in cystic ovaries, and fewer days to first heat with a stress pack containing niacin. Niacin is not palatable and should be incorporated with a palatable carrier (such as distillers grain or molasses) at a rate of 6 g of niacin with 115 g or more of the carrier feed.
ANIONIC SALTS Anionic salts (ammonium chloride, ammonium sulfate, aluminum sulfate, magnesium sulfate, or calcium chloride) cause rations to be more acidic, increasing absorption of dietary calcium and stimulating mobilization of bone calcium. 42 When more blood calcium is available, the cow is able to maintain blood calcium levels when the calcium drain due to milk synthesis occurs. Canadian workers6 reported 48% milk fever when cationic (control) diets were fed and no milk fever with anionic diets. Colorado researchers 42 reported a 13% decrease (from 17 to 4%) when cows received anionic salts with calcium intakes as high as 150 g per day. Feeding 100 g ammonium chloride and 100 g magnesium sulfate for 2 to 3 weeks prepartum has resulted in favorable responses in the field (reduced milk fever and hypocalemia, less retained placenta, and higher dry matter intake postpartum). Anionic salts are unpalatable, should be mixed with 200 to 454 g of a palatable carrier (such as distillers grain, molasses, or heated soybeans), and be pelleted to avoid separation.
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Additional research is needed to determine optimal combinations of anionic salts, levels, and duration of feeding. ASPERGILLUS ORYZAE
Aspergillus oryzae (AO) is a fermentation extract produced from a selected strain of enzyme-producing AO and is marketed under the tradename Amaferm (Bioenzyme Enterprises, Inc., St. Joseph, MO). The fungal additive has its main effect in the rumen, increasing cellulolytic bacteria, shifting VFA fermentation patterns, and stabilizing ruminal pH. Milk yield responses summarized from seven research studies were 28.5 kg for AO-supplemented animals compared with 27.3 kg for control cows (Hallada CM, personal communication, 1990). Arizona researchers 54 reported animals in hot environmental conditions had reduced body temperatures when AO was fed. Additional research is needed to evaluate which type of diet will have optimal economic responses and its role with other rumen additives (such as yeast and buffers). BACTERIAL DIRECT-FED MICROBIALS Bacterial direct-fed microbials (BDFM) or probiotics are microorganisms that have been selected for their ability to assist in maintaining a bacterial balance in the host animal's digestive tract during stressful or disease situations (Hallada CM, personal communication, 1990). Methods BDFM bacteria use to "balance" microHora are complex and unclear, but the following points should be considered. • Production of organic acids, hydrogen peroxide, and/or antibiotics could destroy undesirable microbes. • Lowering the oxidation/reduction potential could limit oxygen availability to pathogens. • The production of beneficial enzymes could improve nutrient availability. • Detoxification of harmful metabolites could improve animal health. Selected BDFM should be able to grow rapidly, colonize in the digestive tract, survive low stomach pH, remain viable during storage, and be compatible with specified antibiotic therapy. General groups of BDFM approved by the FDA include bacillus, bifidobacterium, streptococcus, bactereoeles, lactobacillus, pediococcus, and several other bacterial groups (Hallada CM, personal communication, 1990). Several forms of BDFM are available, including powders (for feed or liquid incorporation), boluses, pastes, and liquids. Additional research to determine optimal combinations, efficiency, target animals, number of colony-forming units per animal or unit of body weight, and economic response are needed before BDFM recommendations can be warranted. BETA-CAROTENE Beta-carotene is a biologic precursor of vitamin A, occurring naturally in feedstuffs (such as alfalfa and corn). Significant loss of beta-carotene occurs during storage of feedstuffs. The NRC (National Research Council) established a beta-carotene requirement of 19 mg of carotene per 100 kg liveweight per
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day.40 However, its additive role is through reproductive improvement and mastitis reduction. One specific role of beta-carotene is regulating host defense in blood lymphocytes through a receptor-binding protein mechanism. 9 Adding 300 mg of beta-carotene reduced milk somatic cell counts compared to unsupplemented coWS. IO ,43 The ability of blood neutrophils to phagocytize and kill bacteria was enhanced in beta-carotene - supplemented cOWS. 9 ,11 Early European research with beta-carotene supplementation improved reproductive performance, with fewer services per conception, fewer days open, and high blood progesterone. 4 However, recent studies have reported no improvement in reproductive performance, blood hormonal levels, or somatic cell counts. 2,5,38 Grave-Hoagland et a1 20 reported that beta-carotene is related to bovine luteal function in vitro during the winter when plasma beta-carotene levels were lower, but that no response occurred in the summer. Folman et al l8 reported that high carotene intake may have adverse effects on dairy cow fertility. Cows fed 500 mg carotene prepartum and 700 mg postpartum had a conception rate (all inseminations) of 27.9% compared to controls of 53.9%, with older cows (fourth and later lactation cows) more adversely affected. The response to beta-carotene is varied, with the immune response and mastitis control requiring further research effort. Beta-carotene is not recommended to improve reproduction when cows receive traditional feedstuffs and supplemental vitamin A.
CHOLINE Choline is usually classified as a B vitamin, but does not fit in the traditional role of a vitamin. Its roles in dairy nutrition include minimizing fatty liver formation, improving neurotransmission, and serving as a methyl donor.I5 The lack of response to dietary choline is due to extensive rumen degradation, estimated to be 85 to 95% of supplemental choline. 16,47 Thus, dietary sources and supplementation are not benencial. 48 Erdman l5 summarized five studies from Wisconsin 21 and Maryland l5 when choline was postruminally infused (15 to 90 g per day). The average milk response to choline was + 1.0 kg per day, +0.17 percent, and + 1.5 kg per day for milk, fat percent, and fat-corrected milk, respectively. The primary mechanism of interest in dairy cows is choline's effect on triglyceride transfer from the liver, especially in early lactation when free fatty acids from adipose tissue are mobilized and formed into lipoproteins, requiring choline-containing phospholipids. Choline could also spare methionine, which otherwise would be used for choline synthesis (10 g of choline would provide the equivalent methyl groups found in 44 g of methionine). Diets low in methionine may be improved by adding 30 g of rumen-protected choline. Choline will be more difficult to protect in the rumen than amino acids because it is extremely hygroscopic. Additional research on protected choline and its direct and indirect roles is needed before it can be recommended.
IONOPHORES Monensin (common brand name is Rumensin [Elanco, Indianapolis, IN]) and lasalocid (common brand name is Bovatec [Hoffman-LaRoche Inc., Nutley, NJ]) are antibiotics that can change rumen fermentation patterns. The initial
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research was conducted with beef cattle. In trials with monensin involving dairy animals, growth improvement ranged from 6 to 14% with no negative effects on reproduction, calving ease, or calf size. Pennsylvania data28 indicated heifers calved 38 days earlier due to improved growth and feed efficiency, resulting in a savings of $62.00. The cost of monensin was 1.2¢ per day or $5.00 per animal, resulting in a benefit to cost ratio of 12: 1. Lasalocid research has similar growth improvement and feed efficiency responses. Lasalocid can be fed to animals below 180 kg and is associated with fewer feed reduction problems when initially fed compared with monensin. Both lasalocid and monensin are labeled as coccidiostats. The modes of action for ionophores include a shifting of VFA and decreasing methane production in the rumen, improving growth and feed efficiency, sparing dietary protein, and changing rumen fill and rate of passage. The benefit of ionophores as coccidiostats is improved growth and health in young animals.
METHIONINE HYDROXY ANALOG Methionine is an essential sulfur-containing amino acid which can be involved in the formation of lipoproteins in the liver. McCarthy37 successfully injected methionine intravenously into cows suffering from ketosis, correcting the disorder. Methionine hydroxy analog (MHA) is chemically similar to methionine and was considered resistant to microbial degradation. However, Wisconsin workers 34 found 99% of MHA was degraded or altered in the rumen. Most of the published research36 with MHA has shown limited improvement in milk yield, but increased milk fat and fat-corrected milk. Minnesota workers 36 conducted three lactation studies in which milk-fat production was improved 10% with 25 to 30 g MHA. Similar results were obtained with 20 g methionine. Factors resulting in positive response to MHA include stage of lactation (first 100 days postpartum), level of milk production (over 23 kg milk), dosage (0.15% MHA of ration dry matter or 30 g), high concentrate diets (over 50%), and lower levels of dietary protein (less than 15%). The possible modes of action include lipoprotein synthesis, increased cellulose digestion, higher rumen protozoa counts, and increased acetate-to-propionate ratio. 36 Rumen responses could explain similar responses with MHA or methionine. Minnesota researchers 36 calculated a net profit of $0.19 per cow per day or $21.25 per cow (fed for 16 weeks postpartum, $0.10 for MHA per day, $13.00 per 45 kg of milk, and $0.17 fat-test differential). MHA can be found in commercial buffer and stress packs. The research with MHA has been variable, with cost a concern. YEAST CULTURE Yeast culture is a live culture of yeast (a fungi) and the media on which it was grown. It is dried so as to preserve the fermenting capacity of the yeast. Several other types of yeast products are available from fermentation processes (such as brewers and distillers yeast). A summary of seven yeast studies 29 concluded that cows fed yeast averaged 25.1 kg of 4% fat-corrected milk compared to control cows at 23.5 kg. However, results are variable and inconsistent. Early lactation cows had a significant increase in milk yield while midlactation cows had no response. 23 Milk composition (fat and protein levels)
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response is also variable. Erdman and Sharman 16 reported no effect of yeast culture on milk fat percent, but a slight increase in milk protein content. The main effect of yeast culture is to stabilize the rumen environment. Concentrations of cellulolytic and anaerobic bacteria were higher in in vitro and in vivo systems. 29 Rumen pH has been elevated in some studies with yeast cultures, but pH changes are not consistent. A decrease in acetate-to-propionate ratio has also been observed, which would favor milk protein synthesis. A reduction in rumen lactic acid concentrations has been reported. 55 Higher dry matter intakes were reported by Florida23 and English workers,55 while other studies showed no difference. 55 Yeast cultures are being studied to determine mode of action, optimum level, and correct stage of lactation during which to feed. Early lactation (2 weeks prepartum to 8 weeks postpartum) appears to be the optimum time to feed yeast culture to stabilize the rumen environment as cows are shifted from dry cow to high-energy diets. 29 Various forms and concentrations of yeast culture products are commercially available.
ZINC METHIONINE Zinc methionine is a compound composed of zinc and methionine. The additive is resistant to degradation by rumen microbes. 24 Zinc methionine was absorbed to a similar extent compared to zinc oxide, but zinc methionine appears to be metabolized differently after absorption with lower urinary excretion and slower rate of decline in plasma zinc. 52 In eight lactation studies in Washington, Colorado, Britain, Illinois, New York, and Arkansas, somatic cell counts averaged 320,000 and 217,000, and milk yield was 30.3 kg and 31.8 kg for control and zinc-supplemented cows, respectively (Schugal LM, personal communication, 1988). However, Ohio researchers found zinc methionine supplementation did not have an effect on wound healing, mastitis, immune response, or plasma zinc levels. 25 Zinc methionine has been reported in the field to harden hoof surfaces and reduce foot disorders. Several concentrations of zinc methionine are commercially available (feed labels must be checked to avoid excessive consumption). The product can be fed under field conditions when a response can be expected, but the effects should be monitored. CONCLUSION Interest in feed additives will continue. Isoacids (a group of short-chain and branch-chain VFA needed by fiber-digesting bacteria) are examples of an additive that was used in the early 1980s, but whose use has since declined because of cost, handling limitations, and research indicating alternative sources of isoacids are synthesized from protein. New additives will appear that can improve milk and growth performance. Table 7 summarizes dairy additives, their level of inclusion, cost per animal per day, and field status ("recommended" refers to additive inclusion as needed, "experimental" indicates additional research and study are warranted, "evaluative" suggests use with careful monitoring in specific situations, and "not recommended" reflects a lack of economic response or research from which to recommend current use.) The status of these additives will change as additional research and field experiences occur.
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MICHAEL FRANCIS HUTJENS
Table 7. Guidelines and Considerations for Dairy Feed Additives COST ADDITIVE
Anionic salts Aspergillus oryzae Bentonite Beta carotene Buffers Sodium bicarbonate Sodium sesquicarbonate Magnesium oxide Choline Ionophore Isoacids Methionine hydroxy analog Niacin Probiotics (BDFM) Yeast culture Zinc methionine
LEVEL
($/DAY)
STATUS
200 g 3g 454-600 g 200-300 mg
0.18 0.05 0.06 0.30
Experimental Experimental Evaluative Not recommended
110-225g 160-340 g 50-90 g 30 g
0.06 0.05 0.02 0.10
Recommended Recommended Recommended Not recommended
0.02 0.20 0.10
Recommended Not recommended Not recommended
50-200 mg 90 g 30 g 6-12 g Varies 10-120 g 5g
0.06-0.12 0.03-0.18 0.06 0.02
Recommended Experimental Evaluative Evaluative
REFERENCES 1. Abdouli H, Schaefer DM: Impact of niacin and length of incubation on protein synthesis, soluble to total protein ratio, and fermentation activity of ruminal microorganisms. J Anim Sci 62:244, 1986 2. Akordor FY, Stone JB, Walton JS, et al: Reproductive performance of lactating Holstein cows fed supplemental beta carotene. J Dairy Sci 69:2173, 1986 3. Armentano LE, Solorzano LC: Buffers for dairy cattle: Mechanisms of action as a basis for formulating buffer mixtures. Nutri News 1:2, 1989 4. Bindas EM, Gwazdauskas FC, Aiello RJ, et al: Reproductive and metabolic characteristics of dairy cattle supplemented with beta carotene. J Dairy Sci 67:1294, 1984 5. Bindas EM, Gwazdauskas FC, McGilliard ML, et al: Progesterone response to human chorionic gonadotropin in dairy cattle supplemented with beta carotene. J Dairy Sci 67:2978, 1984 6. Block E: Manipulating dietary anion and cation for prepartum dairy cows to reduce incidences of milk fever. J Dairy Sci 67:2939, 1984 7. Chalupa W, Ferguson JD, Galligan DT: Feeding the high producing cow. In Am Soc Agric Engineers Proceedings, Harrisburg, 1990, p 14 8. Chase LE: Yeast in dairy cattle feeding program. In Proceedings of the Cornell Nutrition Conference, Syracuse, NY, 1989, P 121 9. Chew BP: Beta carotene and vitamin A nutrition on animal health. In NFIA Nutrition Institute Proceedings, Kansas City, MO, 1990 10. Chew BP, Johnson LA: Effect of supplemental vitamin A and beta carotene on mastitis in dairy cows. J Dairy Sci 68(Suppl 1):191, 1985 11. Dahlquist SP, Chew BP: Effects of vitamin A and beta carotene on mastitis in dairy cows during the early dry period. J Dairy Sci 68(Suppl 1):191, 1985 12. Davis CL: The use of buffers in the ration of lactating dairy cows. In Regulation of Acid-Base Balance. Piscataway, NJ, Church and Dwight, 1979, p 51 13. Downer JV, Cummings KR: A 10 year review of lactation studies. J Dairy Sci 70(Suppl 1):198, 1987 14. Erdman RA: Dietary buffering requirements of the lactating dairy cow. J Dairy Sci 71:3246, 1988 15. Erdman RA: Choline nutrition in dairy cattle. In NFIA Nutrition Institute Proceedings, Kansas City, MO, 1990, P 1 16. Erdman RA, Sharman BK: Effect of yeast culture and sodium bicarbonate on milk yield and composition in dairy cows. J Dairy Sci 72:1929, 1989
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17. Erickson PS: Niacin-lipid interactions in dairy cows (Doctorate Thesis). University of Illinois, Urbana, IL, 1989 18. Folman Y, Ascarelli I, Kraus D, et al: Adverse effects of beta carotene in diet on fertility of dairy cows. J Dairy Sci 70:357, 1987 19. Fronk TJ, Schultz LH: Oral nicotinic acid as a treatment for ketosis. J Dairy Sci 62: 1804, 1979 20. Grave-Hoagland RL, Hoagland TA, Woody CO: Effect of beta carotene and vitamin A on progesterone production by bovine luteal cells. J Dairy Sci 71: 1 058, 1988 21. Grummer RR, Armentano LE, Marcus MS: Lactation response to short-term abomasal infusion of choline, inositol, and soy lecithin. J Dairy Sci 70:2518, 1987 22. Harmeyer J, Grabe CV: The effect of niacin supplement on ketogenesis on the dairy cow. Deutsche Tierarztliche Wochenschrift 88:401, 1986 23. Harris B Jr, Lobo R: Feeding yeast culture to lactating dairy cows. J Dairy Sci 71(Suppl 1):276, 1988 24. Heinrichs AJ, Conrad HR: Rumen solubility and breakdown of metal protein compounds. J Dairy Sci 66 (Suppl 1):47, 1983 25. Heinrichs AJ, Todhunter DA, Murray FA, et al: Zinc-methionine supplementation for dairy cows - a study of effects on plasma zinc, wound healing, mammary health, and immune responses. Ohio State Research Circular 281, 1984 26. Horner JL, Coppock CE, Moya JR, et al: Effect of niacin and whole cottonseed on ruminal fermentation, protein degradability, and nutrient digestibility. J Dairy Sci 71:1239, 1988 27. Horner JL, Coppock CE, Schelling GT, et al: Influence of niacin and whole cottonseed on intake, milk yield and composition, and systemic responses of dairy cows. J Dairy Sci 69:3087, 1986 28. Hutjens MF: Apply the 4 R's to feed additives. Dairy Herd Management, November, 1988 29. Hutjens MF: Feeding the high producing dairy cow: A role for natural additives. In Biotechnology in the Feed Industry. Alltech Technical 4th Proc, Lexington, KY, 1988, p 37 30. Hutjens MF: Applications of rumen buffers and buffer packs in dairy nutrition. In Application of Nutrition in Dairy Practice. Wayne, NJ, American Cyanamid, 1988, p 44 31. Hutjens MF: Niacin in dairy cattle. In NFIA Nutrition Institute Proceedings, Kansas City, MO, 1990 32. Jaster EH, Hartnell GF, Hutjens MF: Effect of feed supplemental niacin on milk production in six dairy herds. J Dairy Sci 66:1046, 1983 33. Jaster EH: Nicotinic acid or nicotinamide for lactating dairy cows. In Proceedings of the Degussa Technical Symposium, Atlanta, GA, 1988, p 3 34. Jones BA, Mohamed OE, Prange RW, et al: Degradations of methionine hydroxy analog in the rumen of lactating cows. J Dairy Sci 71:525, 1988 35. Kutches AJ: The influence of niacin supplementation on milk and fat production in early lactation. Special report. Lonza, Inc, Fair Lawn, NJ, 1983 36. Lundquist RG, Bhargara PK, Linn JG, et al: Methionine hydroxy analog for lactating dairy cattle. In Proceedings of the Minnesota Nutrition Conference, Minneapolis, MN 1982, P 31 37. McCarthy RD, Potter GA, Griel LC: Bovine ketosis and depressed fat test in milk: A problem of methionine metabolism and serum lipoprotein aberration. J Dairy Sci 51:459, 1968 38. Marcek JM, Appell LH, Hoffman CC, et al: Effect of supplemental beta carotene on incidence and responsiveness of ovarian cysts to hormone treatment. J Dairy Sci 68:71,1985 39. Ndwiga CA, Erdman RA, Vandersal JH, et al: Effect of type and site of acid neutralization on voluntary intake of corn silage by dairy heifers. J Dairy Sci 73:1561, 1990 40. National Research Council Committee: Nutrient Requirements of Dairy Cattle, ed 6. National Academy of Sciences, Washington, DC, 1989, p 43 41. Nocek]E, Vanderslice OL, English JE, et al: Evaluation of a nutritional supplement for dairy cows in early lactation. J Dairy Sci 66(suppl1):D16, 1986 42. Oetzel GR, Olson JD, Curtis CR, et al: Ammonium chloride and ammonium sulfate for prevention of parturient paresis in dairy cows. J Dairy Sci 71 :3302, 1988
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43. Rakes AH, Owens MR, Britt JH, et al: Effects of adding beta carotene to rations of lactating cows consuming different forages. J Dairy Sci 68:1732, 1985 44. Riddell DO, Bartley EE, Dayton AD, et al: Effect of nicotinic acid on microbial protein synthesis in vitro and on dairy cattle growth and milk production. J Dairy Sci 64:782, 1981 45. Schultz LH: Niacin in dairy rations. In Pacific N.W. Nutrition Conference Proceedings, Corvallis, OR, 1983 46. Schwab CG: Supplemental niacin for lactating dairy cows. In Proceedings of the 24th Annual New England Dairy Feed Conference, Concord, NH, 1983 47. Sharma BK, Erdman RA: Effects of dietary and abomasally infused choline on milk production responses of lactating dairy cows. J Nutr 119:248, 1989 48. Sharma BK, Erdman RA: In vitro degradation of choline from selected feedstuffs and choline supplements. J Dairy Sci 72:2772, 1984 49. Shaver RD, Erdman RA, Vandersal JH, et al: Effects of silage pH on voluntary intake of corn silage. J Dairy Sci 67:2045, 1984 50. Shields DR, Schaefer DM, Perry TW: Influence of niacin supplementation and nitrogen source on rumen microbial fermentation. J Anim Sci 57:1576, 1983 51. Skaar TC, Grummer RR, Dentine MR, et al: Seasonal effects on prepartum and postpartum fat and niacin feeding on lactation performance and lipid metabolism. J Dairy Sci 72:2028, 1989 52. Spears JW: Zinc methionine for ruminants: relative bioavailability of zinc in lambs and effects on growth and performance of growing heifers. J Anim Sci 67:835, 1989 53. Staples CR, Lough DS: Efficacy of supplemental dietary buffers for lactation cows. In Florida Nutrition Conference Proceedings, Gainesville, FL, 1987 54. Wallentine MV, Johnston NP, Andus D, et al: The effect of feeding Aspergillus oryzae culture-vitamin mix on the performance of lactating dairy cows during periods of heat stress. J Dairy Sci 69(Suppl 1}:189, 1986 55. Williams PEV: The mode of action of yeast culture in ruminant diets: A review of the effect on rumen fermentation patterns. In Biotechnology in the Feed Industry. Alltech Technical 5th Proceedings, Lexington, KY, 1989, p 65 Address reprint requests to Michael Francis Hutjens, BS, MS, PhD University of Illinois 315 Animal Sciences Laboratory 1207 West Gregory Drive Urbana, IL 61801