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Heat Stress Interactions with Protein Supplemental Fat, and Fungal Cultures
Heat Stress Interactions with Protein, Supplemental Fat, and Fungal Cultures J. 1. HUBER,' 0. HIGGINBOTHAM.2 R. A. GOME&ALARCON,3 R. 8. TAYLOR: K. H. CHEN, S. C. CHAN, and 2. WU5 Deparhent of Animal Sciences University of Arizona Tucson 86721 ABSTRACT
less yield response than when fat was added at moderate temperatures. In several studies, fungal cultures (3 to 5 g/ d) in the diet decreased body temperatures and respiration rates in hot, but not cool, weather. Increased milk yields and cellulose digestibility also resulted from dietary fungal cultures in some, but not all, trials. The mechanism of action exerted by fungal cultures on body temperature and respiration rate is unclear. (Key words: heat stress, protein nutrition, fat supplementation, fungal extract)
Cows that were subjected to hot environmental temperatures yielded less milk (3.1 kgld) on a diet high in CP (18.4%) and of medium degradability (65%) than on diets high in CP of low degradability (59%) or medium in CP (16.1%). The high CP diets were associated with decreased DMI and higher water intake, ruminal and blood urea. Negative effects on yield from the high CP, medium degradability diet were not observed at moderate temperatures. Evaporative cooling of cows in hot weather resulted in a greater milk yield response to low versus medium rumenundegradabale protein diets than for uncooled cows. Evaporative cooling of cows also affected response to protein quality. For cooled cows, high Lys diet (soybean, fish, and blood meals) increased milk yield 14% over that with low Lys diet (corn gluten meal), but, for uncooled cows, a high Lys diet only increased yield by 9%,Percentage of CP, degradability, and protein quality had no effect on body temperatures or respiration rates of lactating cows. Some, but not other, reports showed that supplementation of 2 to 2.5% fat to diets fed under hot summer conditions resulted in
m,
Abbreviation key: RDP = rumen-degradable protein, RR = respiration rate, RT = rectal temperature, RUP = rumen-undegradable protein. HEAT STRESS AND PROTEIN NUTRITION
Received June 16, 1993. Accepted October 12, 1993. 'Corresponding author. % m n t address: University of California Agricultural Extension Service, 1720 South Maple, Fnsno 93702. 3 C m n t address: Lindos 14, Paseo Cam Blanca, Hermosillo, Sonora 83007, MCxico. 4Cumnt address: Coast Grain Co., 7000 Menill Avenue, Buildmg 4. Box 7, Chino, CA 91710. %hrent addrcss: Department Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061. 1994 J Dairy Sci 77:2080-2090
Cattle under heat stress often have negative N balances because of reduced intakes; hence, less protein is available for productive functions if dietary protein concentrations are not increased (12, 20, 24, 30). In a hot environment (19 to 31% minimum and maximum daily temperatures), Hassan and Roussel (12) observed increased feed intake, milk yield, and milk protein yield of Holstein cows fed 21% CP compared with those of cows fed 14% CP. Even the 14% CP diet exceeded NRC (30) requirements for protein by 23% but the increased milk was attributed to the higher feed intake elicited by 21% CP. Zook (47) compared two protein solubilities (40 vs. 20%) in lactating cows subjected to heat stress or thermoneutral conditions and observed more milk from cows with less rumendegradable protein O P ) during both hot and moderate conditions; however, CP of rations was only 15%, which is somewhat lower than that fed to many modem herds but apparently in accordance with NRC (30)
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recommendations. Neither rectal temperatures (RT) nor respiration rates (RR)were affected by protein solubility, but they were increased by heat stress. Total CP content of diets fed to dary cows in many regions of the US,particularly in the Southwest, where hot summer temperatures prevail, is commonly as high as 19 to 20% and often exceeds NRC (30) recommendations by 25 to 30%, even though nunen-undegradable protein (RUP)content generally would meet that suggested by NRC (30). The reduced energy consumption and increased energy maintenance requirement during heat stress often results in considerably more protein being metabolized to meet energy requirements of cows than that metabolized at moderate temperatures (1). When excess AA are provided, they are deaminated at an energy cost of synthesizing and excreting the amino group as urea (30, 32) estimated to be 7.3 kcaVg of urea synthesized (39). Resultant increases in blood ammonia can be injurious to cow health (42). Information is limited on the influence of excessive protein intake, varying degradabilities of dietary CP, and quality of RUP fed on milk yields and related physiological functions in lactating cows subjected to high environmental temperatures. An objective of this review is to evaluate recent studies on interactive effects between heat stress and protein nutrition in lactating dairy cows. Most data cited will be from studies recently conducted at the University of Arizona Dairy Cattle Research Center in Tucson.
spring, diets of similar protein concentrations and degradabilities were tested under moderate ambient conditions in Provo, Utah (14). Table 1 summarizes these studies. In the hot environment, milk yields were lower with the high protein, medium RDP diet than with the other three diets. Reduction of milk yield for cows on the high protein (65%) treatment compared with cows on other treatments averaged 3.1 kg/d, which was equivalent to about 2.1 Mcal of NEL, as estimated according to NRC (30). For the respective treatments, mean CP intakes in excess of requirements (30), determined at initiation of treatment, averaged 31, 37, 18, and 16% and were calculated to equal 144, 171, 85, and 80 g of N/d. The energy expenditure for formation of extra urinary N was assumed to be 7.3 kcaVg of N (39); thus, the 75 g/d more N consumed on the high than medium protein diets would have accounted for 548 kcal of additional energy or about 25% of the difference in milk energy produced between high protein, medium RDP diet and the other diets. Oldham (32) calculated that the energy cost for excretion of 100 g of excessive N in urine was 4.21 MJ or about 1 Mcal. Moreover, the lower DMI of cows fed high protein than of those cows fed medium protein equaled about 2.9 Mcal of NEL and might partially explain the lower milk yields on the high protein, medium RDP diet. Why consumption was lower on high than medium protein diets is not clear. Even though initial protein intake on the high protein, low RDP (59% of CP)diet exceeded calculated requirements more than the high protein, medium RDP (65% of CP) diet, the lower RDP diet did not depress milk yield and resulted in greatest Protein Concentration and Dogradability efficiency of feed utilization. Three separate trials involving 60 cows Danfaer et al. (6Jreported that milk energy were conducted during the hot summer months output was reduced 1.08 McaVd of NEL when in Tucson (15). Diets containing high (18.5% dietary CP increased from 19 to 23% of DM. CP) or medium protein (16.1% CP) concentra- The calculated net energy cost used for syntions and two percentages of RDP (65 vs. 59% thesizing extra urea, primarily in the liver, and of total CP) as calculated from NRC (30) were for excreting excess N accounted for the loss compared in a 2 x 2 factorial arrangement of in milk (32). In the Arizona study (15), the HP treatments. During the trials, heat stress condi- diets were 2.4 percentage units higher in CP tions were confmed because mean daily max- than the medium protein diets; the excess proima for temperature-humidity indexes, calcu- tein would explain partially the depressed milk lated according to Johnson and Vanjonack (19) yields observed for high protein (65%) (15). were over 80, although 72 was the The high protein diets increased ruminal temperature-humidity index at which milk N H 3 and blood urea N, but diets with more yields began to decline (19). During late RDP increased blood urea N and water intake. Journal of Dairy Science Vol. 77. No. 7, 1994
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Journal of Dairy Science Vol. 77, No. 7, 1994
HUBER ET AL
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SYMPOSIUM: NUTRITION AND HEAT STRESS TABLE 2. Effect of protein degradability and evaporative cooling on milk yields and feed intakes (38).'
Shaded
Cooled Item
HD
LD
HD
Effects
LD
D
C
D x C
P < Trial 12 Milk yield 3.5% FCM yield DMI MiWDMI Trial 22 Milk yield 3.5% FCM yield DMI MiWDMl
.52 .14
.05 .02 .09 .01
.31 .34 .37 57
.02 .75 .60 .44
.76 .87 .64 .94
.04
31.9 25.7 21.3 1.54
29.9 26.1 21.1 1.47
30.0 24.3 21.8 1.38
29.3 22.9 22.7 1.27
.04 .57
26.8 24.4 23.9 1.18
32.8 26.4 21.6 I .39
29.1 26.1 22.6 1.29
29.6 25.0 23.8 1.24
.04 .09 .03
'Covdate-adjusted means. HD = High degradability, LD = low degradability; D = degradability effect, and C = cooling effect. zFor trial 1, rumen-degradable protein of HD and LD diets was 65 and 55%, respectively; trial 2, respective values were 61 and 47%.
In some studies (2), increased blood urea N has been implicated in depressed reproductive performance, which might be accentuated during heat stress. Rectal temperatures and RR were not affected by dietary protein. However, these measurements were higher in the Arizona study (15) than in the Utah study (14). Rumen VFA. blood glucose, thyroid hormones, and cortisol were not different among diets, but those heat-sensitive hormones (8, 19) all were much lower for cows in Arizona (15) than for cows treated at moderate temperatures in Utah
trial 2. Degradability exerted opposite effects in the trials; milk yields were higher for the 64% RDP in trial 1 but lower for 61% RDP in trial 2. Cooler ambient temperatures and lower temperature-humidity index in trial 1 than 2 (71 vs. 77 average temperature-humidity index) may have negated the significant protein by heat stress interaction observed previously (15) for 3.5% FCM yield. In trial 2, conditions were more conducive to detection of heat stress; maximum daily temperature-humidity index averaged 80 and 83 for cooled and shaded groups, respectively. Rectal tempera(14). At moderate temperatures (14), milk yields tures (39.2 vs. 39.7'C) and RR (70 vs. 88 followed a much different pattern than they did breathdmin) also were lower for the cooled in the hot environment. Yields were lowest for groups. Cows fed 47% RDP yielded more milk the medium protein treatment of higher RDP, (3.4 kg/d) than did those fed 61% RDP, and the perhaps because of insufficient availability of degradability by cooling interaction also was essential AA. Even though total CP met NRC significant; cooled cows responded more to (30)recommendations, intake of RUP was only lower RDP than did uncooled cows. As in the 88% of the recommended amount. Milk fat studies of Higginbotham et al. (14, 15), neither was depressed by the lower RDP diets (14), RT nor RR were affected by protein degradaand water intakes were increased when higher bility. Intakes of RDP in excess of needs appear to RDP was fed (14, 15). In two subsequent trials (38), the interaction be more related to the negative effect of heat of RDP and cooling of cows during hot sum- stress than the percentage composition of RDP mer weather was studied using a factorial ar- in diets. For example, trials 1 and 2 of the rangement of treatments. All diets averaged study of Taylor et al. (38) and the study of 18.3% CP; trial 1 compared 64 with 55% Higginbotham et al. (15) in a hot environment RDP, but RDP estimates of trial 2 were 61 and showed lowest milk yields on diets exhibiting 47%. As shown in Table 2, evaporative cool- highest RDP intakes in excess of requirements ing increased milk yield in trial 1, but not in (30). The data suggest that overconsumption of Journal of Diury Science Vol. 77, No. 7, 1994
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HUBER ET AL.
TABLE 3. Efect of supplemental protein quality and evaporative cooling on feed intake, milk yield, composition, and efticiency of feed utilization during hot weather (5).
Treatment1 Item
HL-Ec+s LL-Ec+s
Trcatment effect
HL-s
LL-S
SEh4
Rotein
Cooling
-P
kgld Protein %
kg/d
25.5 31.9 30.2 28.9 1.23
24.3 28.1 26.6 25.4 1.11
23.9 28.7 27.2 25.0 1.13
22.7 26.3 24.4 24.0 1.08
.9 .9 1.2 1.1 .07
.18 .01 .01 .06 .24
.IO .02 .03 .03 .35
3.20 1.02
3.28 .91
3.22 .91
3.18 .83
.ll .04
.86 .os
.72 .04
3.09
3.07 .87
3.13 .E9
3.22 .84
.06 .04
.60 .03
.14 .09
.99
IHL = High Lys, LL = low Lys,EC+S = evaporative cooling plus S, and S = shade. Covariant-adjusted least squares means. The S cows were higher than EC+S (P c .05)in mean rectal temperatures (39.1 vs. 38.6'C) and respiration rates (82 VS. 64 breaths/min). Mean mnximum ambient temperature was 35.8'C. and mean temperature-humidity index was 76.6
more than 100 g N/d as RDP lowered yield performance. However, further experimentation is required to quantify such a relationship.
9% higher than those of the cows receiving
shade only. Even though interaction effects were not significant, differences in milk yield between the high and low Lys diets were greater for cows evaporatively cooled and shade (3.8 kg/d) than cows receiving receiving Protoln Quallty shade only (2.4 kg/d). Moreover, cooling efA positive response in milk yield or milk fects were greater with the high Lys than on protein concentration to inclusion of an in- the low Lys diets (3.2 kg/d for high Lys vs. 1.8 creased dietary supply of essential AA (5, 46) kg/d for low Lys). Cows in the shaded environto specific AA, such as Lys (22,34, 35) or Lys ment and fed the high Lys diet produced plus Met (33, has been demonstrated in cooler slightly more milk than those fed low Lys and environments. However, little is known con- receiving evaporative cooling plus shade, sugcerning an interaction of protein quality and gesting that protein quality compensated for heat stress. The study of Chen et al. Q ad- lack of cooling in hot weather. dressed this question by comparing a diet of low Lys content (using corn gluten meal as the principal protein supplement) with one contain- Summary ing 67% higher Lys (from a combination of For maintenance of maximum milk yield soybean, fish, and blood meals). Both diets during periods of heat stress of cows fed diets contained about 43% RDP (30),and the con- typical of those in the southwestern US (which tent of other essential AA was similar (except generally contain 18% or more CP), data sugfor Arg, which was higher in the high Lys gest that RDP should not exceed 61% of total diet). The low Lys diet was 19.2% CP and the dietary CP and that RDP should not exceed high Lys was 18.6% CP. Groups received NRC (30) recommendations by more than 100 evaporative cooling plus shade or shade only g of N/d. Additionally, an important protein in a 2 x 2 factorial arrangement of treatments. quality factor affecting milk yield during heat As shown in Table 3, cows fed the high Lys stress is Lys content of diets. Cows fed 1% diet produced 11% more milk than those on Lys in DM or 241 g/d of dietary Lys produced low Lys, and milk yields of cows evapora- 3 kg more milk than those fed .6% Lys (137 g/ tively cooled and receiving shade were about 4. Journal of Dairy Science Vol. 77, No. 7, 1994
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SYMPOSIUM: NUTRITION AND HEAT STRESS
TABLE 4. Effect of fat supplementation and evaporative cooling on performance of dairy cows in hot summer (3). Tmbnentl Item
MF+S
HP+S
MF+Ec
HF+EC
SEM
DMI, kg/d Milk: kg/d FCM/DMI Milk protein.3 5% Milk fat, % BreWmin Rectal temperature, 'C
26.2 29.5 1.06 2.99 2.93 81.1 39.4
24.7 30.0 1.18 2.95 3.93 85.7 39.4
25.5 31.0 1.15 2.90 3.25 81.2 39.1
24.6 31.7 1.21 2.94 3.13 84.4 39.4
2.6 1.8 .05
.04 .12 5.2 .2
lAdaptcd kom Chan et al. (3). MF+S = Medium fat (4.9%). pen shade; HF+S = high fat (7.7%), pen shade; MF+EC = medium fat, evaporative cooling; and HF+EC = high fat, evaporative cooling. Fat source was prilled fatty acids (Energy Booster 100. furnished by MilL Specialties Co., D u n k , IL). Zcooling effect (P c .08). 3Fat effect (P < .11).
SUPPLEMENTAL FAT AND HEAT STRESS
conducted during hot summer temperatures Supplemental fat for lactating cows has (mean RT of cows was 39.3'C and RR was 83 been a common dietary practice. The possibil- breaWmin) showed only small increases in ity that added fat alleviates heat stress by milk yields (.6 kg) in EC or uncooled cows fed providing nonfermentative energy (26, 40) to 2.5% added prilled fatty acids (Table 4),when cows is of interest. In a study by Moody et al. compared with controls, but EC significantly (29), supplementation of 10% fat ( h m soy- (P < .OS) improved yield (1.6 kg), regardless of bean oil or hydrogenated vegetable fat) in diets fat supplementation. The Arizona studies (3, 4, of thermally stressed cows did not increase 18) suggested that response from added fat is milk yield. Moreover, such high percentages of less for heat-stressed than unstressed cows (Taruminally unprotected fat, particularly from ble 5). Our hypothesis, that added fat would reduce soybean oil, likely would depress fiber digestion if it were included in diets for high yield- heat of fermentation during hot summer teming dairy cows (33). peratures, apparently was erroneous because, More recently, added fat (from whole oil- in support of the study by Moody et al. (29), seeds or commercial fat sources) has been fed neither RT nor RR decreased in cows fed to heat-stressed cows in commercial herds. supplemental fat compared with those of cows Rumen-inert fat, such as calcium soaps of fatty fed no added fat (3, 4). acids, prilled fatty acids, or saturated triglycerThose studies are in apparent contrast with ides (tallow), which minimizes fatty acid inhi- that of Skaar et al. (37), who showed that fat bition of rumen microorganisms (33), has been supplementation tended to increase milk yield added at 2 to 3% of DM to alfalfa-based diets of cows that calved during the warm, but not containing whole cottonseed and increased the cool, season; however, maximum temperamilk yields about 2 kgld (18). However, total tures of the warm months did not exceed 3 5 T , fat content of dietary DM should not exceed 6 and amount of added fat was double (5%) that to 7 % (18, 33). of the Arizona studies. Knapp and Grummer One study at the University of Arizona (3) in heat-stressed cows subjected to maximum (23) also fed 5% prilled fatty acids to groups of daily temperatures of over W C , with mean cows housed in environmental chambers in a RT of 39.6'C and RR of 85 breathdmin, Latin square design with 15-d periods; those showed increased milk yield (1.2 kg) and milk researchers showed a l.l-kg/d nonsignificant fat (.2 percentage units) from diets containing increase in milk yield for cows in the cool alfalfa hay, 10% whole cottonseed, and 2.5% environment fed added fat compared with supplemental fat as prilled fatty acids com- yield of controls, but only a .3-kg/d increase pared with diets without prilled fatty acids. A for cows kept in the warm environment. Howsecond study in Arizona (4)with similar diets ever, 3.5% FCM yields were increased (P < Journal of Dairy Science Vol. 77, No. 7, 1994
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HUBER ET AL.
TABLE 5 . Response to added fat in hot or moderate temperatures (18). Ambient temperature
DMI Reference Control
EB2
-W d ) Hot Hot Moderate Moderate
(4)
(3) (16) (16)
22.9 25.8 24.2 27.2
Milk yield
NEL Intake1
24.0 24.7 25.3 26.8
Control
EB2
-&idd)37.3 42.3 40.6 44.6
41.0 42.1 45.3 46.4
Control
EB2
32.9 30.3 31.6 32.6
34.la 30.9 34.2' 34.33
Milk protein EB2
Control
-W d ) - - (%)
3.14 2.95 3.13 3.03
3.10 2.95 3.01b 3.08
aSignificantly higher than control (P < .lo). bSignificantly lower than control (P < .OS). 1Estimated from M C (30). *EB = Energy Booster 100 (Milk Specialties Co., Dundee, IL).
.OS) because the supplemental prilled fatty acids increased fat content of milk. Further study is needed to delineate clearly the effects of heat stress on response to fat supplementation. These studies should allow for adequate adaptation of cows to hot weather and should establish a response gradient to varying amounts of added fat during heat stress.
fected tolerance of dairy cows to hot environments (16). The principal species from which these cultures were derived are strains of Aspergillus oryzae and Saccharomyces cerevisiae. This discussion evaluates the effects of fungal cultures on body temperatures and FtR as related to heat stress and the effects on milk yield and composition in lactating cows. Rumen changes related to yield responses also are mentioned. The trade name of the A. oryzae cultures that has undergone most investigation is Amaferm@(BioZyme EnFUNGAL CULTURES AND HEAT STRESS terprises, St. Joseph, MO), and those of S. Fungal cultures have been marketed as feed cerevisiae are YeaSaccB (Alltech Biotechnoladditives for livestock and reportedly have af- ogy Center, Nicholasville, KY) and Diamond
TABLE 6. Rectal temperatures (RT) and respiration rates (RR) of cows fed Aspergillus oryme extract (AOE). RT Reference (17)
Trial
Control
AOE
Control
AOE
1 2
39.4 39.8 40.1 39.2 39.0 38.7 39.1 39.1 38.8 38.8 39.3 38.8
38.43 39.3' 39.Y 39.w 38.7 38.5 39.2b 39.1 38.8 38.8 39.3 38.7'
. . . ...
...
67
63
. . .
...
79
82
(25)
...
(10)
1 2 31 1 2
(43)
(21)
0 (13)
RR
...
1 2
...
... ...
...
... I
.
.
70 51
3Mean differences for all measurements lower for AOE than control (P < .05). bMean differences of measurements in early lactation cows higher for AOE than control (P < .OS). CAbout one-half of weekly means lower for AOE than control (P < .05). 'Means of diurnal changes in inner ear for seven cows per treatment. Journal of Dairy Science Vol. 77, No. 7, 1994
...
...
...
...
... ...
74 52
SYMPOSIUM: NUTRITION AND HEAT STRESS
2087
specific influence of fungal metabolites on temperature control centers has been suggested. Meyers (28) reported that a number of compounds elaborated from fungi affect temEffects on UT and RR perature control centers in animals. Typical of Heat-stressed cows in several studies fed such an effect is the decreased body temperaextract of A. oryzae had lower RT, RR, or ture observed in cows fed aflatoxin (Aspergilboth, than companion controls (10, 13, 17, 25), lus f2avus) (27). One might postulate that the enhanced nueven though the magnitude of effects has been variable (Table 6). In other trials, RT of cows trient utilization and increased milk yields that fed A. orywe were not decreased (7, 21) or sometimes occurred when fungal additives tended to be increased (43) compared with were fed would tend to increase, instead of to controls. In one trial with a yeast culture (16), decrease, body temperatures. Such an effect significantly decreased RT were reported for occurred in one study (43) with cows that were cows fed the culture in the early stages of the not subjected to high ambient temperatures. study, but differences did not continue The group of cows in that study were fed A. throughout the entire trial. Because of a lack of oryzae in early lactation and showed signifidata pertaining to heat stress and S. cerevisiae cantly higher milk yields than controls did, but cultures (16), these additives are not be dis- they also had higher RT and RR; however, cussed further. However, many of the effects milk yield and temperatures of the midlactashown for A. oryzae cultures also have been tion group were not affected significantly by demonstrated for yeast cultures (16, 45). In an Arizona study, water intake was the additive. Greatest increases in milk yields slightly higher for cows fed A. oryzae, and no in the early lactation cows fed fungal culture effect on DMI was reported (10). It is not occurred when environmental temperatures likely that the higher water intake would re- were highest (43). Because cows were group duce body temperatures during heat stress, and fed, individual DMI could not be measured, the lack of difference in DMI suggests that but group intakes were the same for both heat of fermentation was not affected. A treatments (21 kg/d).
V Yeast Culture@ (Diamond V Mills, Cedar Rapids, IA).
TABLE 7. Effect of dietary Aspergillus oryzne extract (AOE) on Reference
Trial
(11)
...
(41) (1V (43)
...
1 2 1 2
(23
...
(10)
1 2
(21)
0 (36) (13) Mean
...
1 2
...
... ...
Control
AOE
24.1 24.1 18.5 18.6 30.1 29.0 28.7 22.3 37.3 26.0 30.9 26.6 30.8 39.3 27.6
26.58 25.0 20.4' 18.6 33.6. 27.8 30.2' 23.2 39.83 27.7b 30.82 25.8 30.8 39.6 28.6
-W d ) -
cows
milk yields.
Remarks
(no)
...
34 32 48 48 50 50 205 24 46 100 40 24 12 110
Normal concentrate Low concentrate Started 0 to 60 D M Started 61 to 120 DIM Commercial herd (6 mo) Midlactation Early lactation Complete lactation Early lactation Midlactation Two concentrate levels early to midlactation Midlactation
...
. . .
...
aSignificantly higher than control (f < .05). bHigher in early and late lactation (f < .05). 1Data presented as milk yields and all others as 3.5 or 4% FCM. *Mean of 1.5, 3, and 6 g/d. Journal of Dairy Science Vol. 77, No. 7, 1994
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HUBER ET AL.
TABLE 8. Relationship between dietary Aspergillus oryzoc extract (AOE) and milk composition. ~
~~
~
Millr fat Reference
Trial
Control
AOE
(23
...
(10)
1 2 1 2
3.64 2.97 3.07 3.74 3.97 3.73 3.51 3.22 3.49
3.77 2.93 2.99 3.81 3.90 3.68 3.46 3.36 3.49
0 (21) (36) (13) Mean
...
... ... .
I
.
~
~
~
Control
~
Milk lactose
Milk protein
AOE
Control
AOE
...
...
...
...
3.15 3.02 2.92 3.42
3.20 2.99 2.97 3.24
4.78 4.99 4.83 4.73
5.01 5.03 4.82 4.71
3.21 3.05 3.13
3.18 3.12. 3.12
...
...
... ...
4.94 4.85
...
...
4.95 4.90
aSignificantIy higher than control (P e .05).
As might be surmised, considerably more study is needed to clarify the relationship between dietary fungal additives to rations of dairy cows and their tolerance to heat stress. Further investigation should clearly establish whether a relationship exists between sup plemental dietary fungal extracts and alleviation of heat stress and clarify the mechanism that might elicit such action.
Effecta on Milk Yields and Compoiltlon
In 14 lactation comparisons involving 823 cows, 3 g/d of A. oryzue extract were fed. Mean increases in milk yields of treated cows over controls was 1.0 kg/d (28.6 vs. 27.6 kg/d for A. oryzae vs. control groups) or 4% (Table 7). Cows fed extract were significantly higher in 6 comparisons, slightly higher in 3, and no different or slightly lower in the remaining 5. Data suggest that early lactation cows fed a higher proportion of concentrate responded more to A. oryzae than did those in mid or late lactation. Williams and Newbold (45) observed greater increases in milk yields for cows supplemented with yeast culture when they were fed high than low energy diets. No consistent effect of A. oryzue extract on milk composition was observed (Table 8). Even though Higginbotham et al. (13) reported significantly higher milk protein, magnitude of increase was only .07 percentage units. Based on increases in milk protein and SNF, those researchers (13) suggested that A. oryzae exJournal of Dairy Science Vol. 77, No. 7, 1994
tract usually would be profitable in diets for high producing herds when milk is priced on the basis of protein, SNF, or both. Several ruminal effects of fungal extracts have been associated with improved performance, including increased digestibility of fiber (9, 10, 44, 45) and other dietary components (9, 10) measured in situ (9), in vitro (9), or in vivo (10, 44, 43, particularly on high concentrate diets; greater numbers of cellulolytic bacteria (44);increased rate of turnover of ruminal lactic acid (31, 45); and less diurnal variation in rumen pH, ammonia, and W A , resulting in greater rumen stability (16, 45). A possible relationship among these factors and greater tolerance to heat stress elicited by fungal extracts, if such an effect exists, is yet to be clarified. CONCLUSIONS
The dietary protein fed to cows in hot environments should not exceed the NRC (30) requirement by more than 10 to 15% of total CP and generally would be less than 18% CP. The RDP of high protein diets should not exceed 61% (of CP) or 100 g of N/d. A high Lys content of dietary RUP gave more favorable responses in milk yield of cooled than uncooled cows. In some studies, when 2 to 3% fat was added to diets containing whole cottonseed, cows subjected to hot temperatures increased less in milk yield than did cows in moderate temperatures; contrasting results were shown in other studies. The consistent decrease in milk protein content from sup-
SYMPOSIUM: NUTRITION AND HEAT STRESS
plemental fat does not always occur at hot temperatures. Cultures from A. oryzae (3 g/d) decreased body temperature and increased milk yields in some investigations, but, despite more studies showing a beneficial than an absence of effect by the culture, results have been somewhat inconsistent. REFERENCES 1 Beede, D. K.,and R. J. Collier. 1986. Potential nutritional strategies for intensively managed caale during thermal m s s . J. Anim. Sci. 62543. 2 Chalupa, W., and J. D. Ferguson. 1989. The impact of nutrition on reproduction of cows. Page 59 in Roc. Minnesota Nu&. Conf., Bloomington. 3 Chan, S. C.. J. T. Huber, Z. Wu, K. H. Chen, and J. Simas. 1992. Effect of fat supplementation and protein source on performance of dairy cows in hot environmental temperatures. J. Dairy Sci. 75(Suppl. 1): 175.(Abstr.) 4 Chan, S. H.,J. T. Huber, Z. Wu. J. Simas,K. H. Chen, F. Santos, A. Rodrigues. and J. Varela. 1993. Effects of supplementation of fat and evaporative cooling of dairy cows subjected to hot temperatures. J. Dairy Sci. 76:(Suppl. 1):184.(Abstr.) 5Chen. K. H.,J. T. Huber, C. B. Theurer, D. V. Armstrong, R. Wanderley, J. Sirnas, S. C. Chan. and J. Sullivan. 1993. Effect of supplemental protein quality and evaporative cooling on ladation performance of Holstein cows in hot weather. J. Dairy Sci. 76819. 6Danfaer, A,, 1. Thysen, and V. Ostergiwd. 1980. The effect of the level of dietary protein on milk production. 1. Milk yields, liveweight gain and health. Bent. Statens Husdrbmgsfors. 492. 7Dcnigan. M. E., J. T. Huber, G. Alhadhrami, and A. Al-Dehneh. 1992. Influence of feeding varying levels of AmafermQ on performance of lactating dairy cows. J. Dairy Sci. 75:1616. 8Deres2, F. 1987. Effect of diffmnt cooling systems on concentrations of certain hormones and free fatty acids at varying times during lactation of Holstein cows. Ph.D. Diss., Univ. Arizona, Tucson. Univ. Microfilms Int., Ann Arbor, MI. 9Gomez-Alarcon, R. A., D. Dudas, and J. T. Huber. 1990. Influence of Aspergillus oryzae on mmen and total tract digestion of dietary components. J. Dairy Sci. 73:703. 10Gomez-Alarcon, R. A,, J. T. Huber, G. E. Higginbotham. F. Wiersma, D. Ammon. and B. Taylor. 1991. Influence of feeding an Aspergillus o r y m culture on the milk yields, eating patterns, and body t e m p e m s of lactating cows. J. Anim. Sci. 69:1733. 11 Harris, B., Jr.. H. H. Van Horn, K.E. Manookian, S. P. Marshall, M. J. Taylor, and C. J. Wilcox. 1983. Sugarcane silage, sodium hydroxide and steam pressure-treated sugarcane bagasse, com silage, cottonseed hulls, sodium bicarbonate, and Aspergillus oryzae product in complete rations for lrrctating cows. J. Dairy Sci. 66:1474. 12 Hassan. A., and J. D. Roussel. 1975. Effect of protein concentration in the diet on blood composition and
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productivity of lactnting Holstein cows under thermal stress. J. Agric. Sci. (Camb.) 85:409. 13Higginbotham, G. E.,D. L. Bath, and L. J. Butler. 1993. Effect of feeding Aspergillus oryzne extract on milk production and related responses in a commercial dairy herd. J. Dairy Sci. 76:1484. 14Higginbotham, G. E.,J. T. Huber, W. V. Wallentine, N. P. Johnston, and D. Andrus. 1989. Influence of protein percent and degradability on performance of 1eCtating cows during moderate temperature. J. Dairy Sci. 72:1818. 15HigginbOtham. G. E.,M. Torabi, and J. T. Huber. 1989. Influence of dietary protein concentration and &gradability on performance of lactating cows during hot environmental temperature. J. Dairy Sci. 72:2554. 16 Huber, J. T. 1990. The fungal and yeast culture story in lactating dairy cows. Page 87 in Roc. Southwest Nutr. Manage. Conf., Tempe, AZ. Dep. Anim. Sci.. Univ. Arizona, Tucson. 17 Huber, J. T.. and G. E.Higginbotham. 1985. Influence of feeding Vitaferm, containing an enzyme-producing culture tiom Aspergillus oryzae, on performance of lactating cows. J. Dairy Sci. 68(Suppl. 1):122.(Abstr.) 18Huber, J. T., 2. Wu, S. C. Chan, and J. Simas. 1993. Feeding of fat during heat stress conditions, and combinations of fat sources. Page 90 in Proc. Southwest Nutr. Manage. Conf., Phoenix, AZ. Dep. Anim. Sci., Univ. of Arizona, Tucson. 19 Johnson, H.D.. and W.J. Vanjonack. 1976. Effects of environmental and other stressors on blood hormone patterns in lactating cows. J. Dairy Sci. 59:1603. 20Kamal, T. H., and H. D. Johnson. 1970. Whole body 4OK loss as a predictor of heat tolerance in cattle. J. Dairy Sci. 58:1734. 21 Kcllems, R. 0..A. Lagerstedt, and M. V. Wallentine. 1990. Effect of feeding Aspergillus oryzae fermentation extract or Aspergillus oryroe plus yeast culture plus mineral and vitamin supplement on performance of Holstein cows during a complete lactation. J. Dairy Sci. 73~2922. 22King. K. J., W. G. Bergen, C. J. Sniffen, A. L. Grant, D. 8. Grieve, V. L. King, and N. K.Ames. 1991. An asstssment of absorbable lysine requirements in lactating cows. J. Dairy Sci. 74:2530. 23 Knapp, D. M.. and R. R. Grummer. 1991. Response of lactating dairy cows to fat supplementation during heat stress. 742573. 24Lcighton, R. E..and I. W. Rupel. 1960. Effects of protein content of the ration on hot weather performance of producing dahy cows. J. Dairy Sci. 43:443. 25Marcus. K. M.. J. T. Huber, and S. Cramer. 1986. Influence of feedig Vitaferm during hot weather on performance of lactating cows in a large dairy herd. J. Darry Sci. 69(Suppl. 1):188.(Abstr.) 26 Mchwell, R. E.,E. G. Moody, P. J. Van Soest, R. P. Lchmann, and G. L. Ford. 1969. Effect of heat stress on energy and water utilization of lactating cows. J. Dairy Sci. 52:188. 27 Mertens, D. R. 1979. Biological effects of mycotoxins upon rumen function and lactating dairy cows. Page 118 in Interaction of Mycotoxins in Animal Pmduction. Natl. A d . Sci., Washington, DC. 28 Meyers, R. D. 1974. Handbook of Drug and Chemical Stimulation of the Brain. Van Nostrand Reinhold Co., New Yo&. NY.
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29 Moody, E. G., P. J. Van Soest, R. E. McDowell, and G. L. Ford. 1967. Effect of high temperature and dietary fat on performance of lactating cows. J. Dairy Sci. 50:1909. 30 National Research Council. 1989. Nutrient Requirements of Dairy Cattle. 6th rev. d.Nd. Acad. Sci.. Washington, DC. 31 Nisbet, D. J., and S. A. Martin. 1990. Effect of dicarboxylic acids and Aspergillus oryme fermentation extract on lactate uptake by the ruminal bacterium Selenomonas ruminantiurn. Appl. Environ. Microbiol. 56:3515. 32 Oldham, J. D. 1984. Proteinenergy interrelationships in dairy cows. J. Dairy Sci. 67:1090. 33 Palmquist, D. L. 1987. Adding fat to dairy diets. Page 35 in Animal Health and Nutrition. Watt Publ. Co., Mt. Moms, IL. 34Polan. C. E., K. A. Cummins, C. J. Sniffen, T. V. Muscato, I. L. Vicini, B. A. Crooker, J. H. Clark, D. G. Johnson, D. E. Otterby, B. Guillaume, L. D. Muller, G. A. Varga, R. A. Murray, and S. B. PeirccSandner. 1991. Responses of dauy cows to s u p plemental rumen-protected forms of methionine and lysine. J. Dairy Sci. 742997. 35 Schwab, C. G. 1993. Amino acid limitation and flow to duodenum at four stages of laaation. 1. Sequence of lysine and methionine limitation. J. Dairy Sci. 75: 3486. 36Sievert, S. J., and R. D. Shaver. 1992. Carbohydrate and Aspergillus oryzae effects on intake, digestion, and milk production by dairy cows. J. Dairy Sci. 7 6 245. 37Skaar. T.C., R. R. Grummer. M. R. Dentine, and R. H. Stuffacher. 1989. Seasonal effects of prepartum and postpartum fat and niacin feeding on lactation performance and lipid metabolism. J. Dairy Sci. 72: 2028. 38Taylor. R. B., 1. T. Huber, R. A. Gomez-Alarcon, F. Wiersma, and X. Pang. 1991. Influence of protein degradability and evaporative cooling on performance of dairy cows during hot environmental temperatures. J. Dairy Sci. 74:243. 39Tyrrell. H. F., P. W. Moe, and W. P. Flu. 1970. Influence of excess protein intake on energy metabo-
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lism of the dairy cow. Page 69 in Energy Metabolism of Farm Animals, Proc. 5th Symp. Energy Metab. Vitmau. Switzerland. A. Schurch and C. Wenk, ed. Eur. Assoc. Anim. Prod. Publ. No. 13. Juris Druck and Verlag, Zurich, Switzerland. 40Tyrrell. H. F., P. J. Reynolds, and P. W. Mce. 1979. Effect of diet on partial efficiency of acetate use for body tissue synthesis by mature cattle. J. A n i . Sci. 48598. 41 Van Horn,H.H., B. Harris,Jr., M. J. Taylor, K. C. Bachman, and C. J. Wilcox. 1984. By-product feeds for lactating dairy cows: effects of cottonseed hulls, corrugated paper, peanut hulls, sugarcane bagasse, and whole cottonseed with additives of fat, sodium bicarbonate, and Aspergillus oryzae product on milk production. J. Dairy Sci. 67:2922. 42 Visek, W. J. 1984. Ammonia: its effects on biological systems, metabolic hormones, and reproduction. J. Dairy Sci. 67:481. 43Wallentine. M. V, N. P. Johnston, D. Andrus, R. Jones, J. T. Huber, and G. E. Higginbotham. 1986. The effect of feeding Aspergillus oryzae culturevitamin mix on the performance of lactating dairy cows during periods of heat stress. J. Dairy Sci. 69(Suppl. 1):189.(AbStr.) 44 Weidmeier, R. D., M. J. Arambel, and J. L. Walters. 1987. Effect of yeast culture and Aspergillus o w e fermentation extract on ruminal characteristics and nutrient digestibility. J. Dairy Sci. 70:2063. 45 Williams, P.E.V., and C. J. Newbold. 1990. Rumen probiosis: the effects of novel microorganisms on rumen fermentation and ruminant productivity. Page 211 in Recent Advances in Animal Nutrition. W. Haresign and D.J.A. Cole, ed. Buttenvorths, London, England. 46 Wohlt, J. E.,S. L. Chmiel, P. K. Zajac, L. Backer, D. B. Blethen, and J. L. Evans. 1991. Dry matter intake, milk yield and composition, and nitrogen use in Holstein cows fed soybean, fish, or corn gluten meals. J. Dairy Sci. 741609. 47 Zook, A. B. 1982. The effects of two levels of dietary protein solubility on lactating cows exposed to heat smss and in thermal neutral environments. Ph.D. Diss., Univ. Missouri, Columbia.
less yield response than when fat was added at moderate temperatures. In several studies, fungal cultures (3 to 5 g/ d) in the diet decreased body temperatures and respiration rates in hot, but not cool, weather. Increased milk yields and cellulose digestibility also resulted from dietary fungal cultures in some, but not all, trials. The mechanism of action exerted by fungal cultures on body temperature and respiration rate is unclear. (Key words: heat stress, protein nutrition, fat supplementation, fungal extract)
Cows that were subjected to hot environmental temperatures yielded less milk (3.1 kgld) on a diet high in CP (18.4%) and of medium degradability (65%) than on diets high in CP of low degradability (59%) or medium in CP (16.1%). The high CP diets were associated with decreased DMI and higher water intake, ruminal and blood urea. Negative effects on yield from the high CP, medium degradability diet were not observed at moderate temperatures. Evaporative cooling of cows in hot weather resulted in a greater milk yield response to low versus medium rumenundegradabale protein diets than for uncooled cows. Evaporative cooling of cows also affected response to protein quality. For cooled cows, high Lys diet (soybean, fish, and blood meals) increased milk yield 14% over that with low Lys diet (corn gluten meal), but, for uncooled cows, a high Lys diet only increased yield by 9%,Percentage of CP, degradability, and protein quality had no effect on body temperatures or respiration rates of lactating cows. Some, but not other, reports showed that supplementation of 2 to 2.5% fat to diets fed under hot summer conditions resulted in
m,
Abbreviation key: RDP = rumen-degradable protein, RR = respiration rate, RT = rectal temperature, RUP = rumen-undegradable protein. HEAT STRESS AND PROTEIN NUTRITION
Received June 16, 1993. Accepted October 12, 1993. 'Corresponding author. % m n t address: University of California Agricultural Extension Service, 1720 South Maple, Fnsno 93702. 3 C m n t address: Lindos 14, Paseo Cam Blanca, Hermosillo, Sonora 83007, MCxico. 4Cumnt address: Coast Grain Co., 7000 Menill Avenue, Buildmg 4. Box 7, Chino, CA 91710. %hrent addrcss: Department Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061. 1994 J Dairy Sci 77:2080-2090
Cattle under heat stress often have negative N balances because of reduced intakes; hence, less protein is available for productive functions if dietary protein concentrations are not increased (12, 20, 24, 30). In a hot environment (19 to 31% minimum and maximum daily temperatures), Hassan and Roussel (12) observed increased feed intake, milk yield, and milk protein yield of Holstein cows fed 21% CP compared with those of cows fed 14% CP. Even the 14% CP diet exceeded NRC (30) requirements for protein by 23% but the increased milk was attributed to the higher feed intake elicited by 21% CP. Zook (47) compared two protein solubilities (40 vs. 20%) in lactating cows subjected to heat stress or thermoneutral conditions and observed more milk from cows with less rumendegradable protein O P ) during both hot and moderate conditions; however, CP of rations was only 15%, which is somewhat lower than that fed to many modem herds but apparently in accordance with NRC (30)
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SYMPOSIUM: NUTRITION AND HEAT STRESS
208 1
recommendations. Neither rectal temperatures (RT) nor respiration rates (RR)were affected by protein solubility, but they were increased by heat stress. Total CP content of diets fed to dary cows in many regions of the US,particularly in the Southwest, where hot summer temperatures prevail, is commonly as high as 19 to 20% and often exceeds NRC (30) recommendations by 25 to 30%, even though nunen-undegradable protein (RUP)content generally would meet that suggested by NRC (30). The reduced energy consumption and increased energy maintenance requirement during heat stress often results in considerably more protein being metabolized to meet energy requirements of cows than that metabolized at moderate temperatures (1). When excess AA are provided, they are deaminated at an energy cost of synthesizing and excreting the amino group as urea (30, 32) estimated to be 7.3 kcaVg of urea synthesized (39). Resultant increases in blood ammonia can be injurious to cow health (42). Information is limited on the influence of excessive protein intake, varying degradabilities of dietary CP, and quality of RUP fed on milk yields and related physiological functions in lactating cows subjected to high environmental temperatures. An objective of this review is to evaluate recent studies on interactive effects between heat stress and protein nutrition in lactating dairy cows. Most data cited will be from studies recently conducted at the University of Arizona Dairy Cattle Research Center in Tucson.
spring, diets of similar protein concentrations and degradabilities were tested under moderate ambient conditions in Provo, Utah (14). Table 1 summarizes these studies. In the hot environment, milk yields were lower with the high protein, medium RDP diet than with the other three diets. Reduction of milk yield for cows on the high protein (65%) treatment compared with cows on other treatments averaged 3.1 kg/d, which was equivalent to about 2.1 Mcal of NEL, as estimated according to NRC (30). For the respective treatments, mean CP intakes in excess of requirements (30), determined at initiation of treatment, averaged 31, 37, 18, and 16% and were calculated to equal 144, 171, 85, and 80 g of N/d. The energy expenditure for formation of extra urinary N was assumed to be 7.3 kcaVg of N (39); thus, the 75 g/d more N consumed on the high than medium protein diets would have accounted for 548 kcal of additional energy or about 25% of the difference in milk energy produced between high protein, medium RDP diet and the other diets. Oldham (32) calculated that the energy cost for excretion of 100 g of excessive N in urine was 4.21 MJ or about 1 Mcal. Moreover, the lower DMI of cows fed high protein than of those cows fed medium protein equaled about 2.9 Mcal of NEL and might partially explain the lower milk yields on the high protein, medium RDP diet. Why consumption was lower on high than medium protein diets is not clear. Even though initial protein intake on the high protein, low RDP (59% of CP)diet exceeded calculated requirements more than the high protein, medium RDP (65% of CP) diet, the lower RDP diet did not depress milk yield and resulted in greatest Protein Concentration and Dogradability efficiency of feed utilization. Three separate trials involving 60 cows Danfaer et al. (6Jreported that milk energy were conducted during the hot summer months output was reduced 1.08 McaVd of NEL when in Tucson (15). Diets containing high (18.5% dietary CP increased from 19 to 23% of DM. CP) or medium protein (16.1% CP) concentra- The calculated net energy cost used for syntions and two percentages of RDP (65 vs. 59% thesizing extra urea, primarily in the liver, and of total CP) as calculated from NRC (30) were for excreting excess N accounted for the loss compared in a 2 x 2 factorial arrangement of in milk (32). In the Arizona study (15), the HP treatments. During the trials, heat stress condi- diets were 2.4 percentage units higher in CP tions were confmed because mean daily max- than the medium protein diets; the excess proima for temperature-humidity indexes, calcu- tein would explain partially the depressed milk lated according to Johnson and Vanjonack (19) yields observed for high protein (65%) (15). were over 80, although 72 was the The high protein diets increased ruminal temperature-humidity index at which milk N H 3 and blood urea N, but diets with more yields began to decline (19). During late RDP increased blood urea N and water intake. Journal of Dairy Science Vol. 77. No. 7, 1994
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HUBER ET AL
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SYMPOSIUM: NUTRITION AND HEAT STRESS TABLE 2. Effect of protein degradability and evaporative cooling on milk yields and feed intakes (38).'
Shaded
Cooled Item
HD
LD
HD
Effects
LD
D
C
D x C
P < Trial 12 Milk yield 3.5% FCM yield DMI MiWDMI Trial 22 Milk yield 3.5% FCM yield DMI MiWDMl
.52 .14
.05 .02 .09 .01
.31 .34 .37 57
.02 .75 .60 .44
.76 .87 .64 .94
.04
31.9 25.7 21.3 1.54
29.9 26.1 21.1 1.47
30.0 24.3 21.8 1.38
29.3 22.9 22.7 1.27
.04 .57
26.8 24.4 23.9 1.18
32.8 26.4 21.6 I .39
29.1 26.1 22.6 1.29
29.6 25.0 23.8 1.24
.04 .09 .03
'Covdate-adjusted means. HD = High degradability, LD = low degradability; D = degradability effect, and C = cooling effect. zFor trial 1, rumen-degradable protein of HD and LD diets was 65 and 55%, respectively; trial 2, respective values were 61 and 47%.
In some studies (2), increased blood urea N has been implicated in depressed reproductive performance, which might be accentuated during heat stress. Rectal temperatures and RR were not affected by dietary protein. However, these measurements were higher in the Arizona study (15) than in the Utah study (14). Rumen VFA. blood glucose, thyroid hormones, and cortisol were not different among diets, but those heat-sensitive hormones (8, 19) all were much lower for cows in Arizona (15) than for cows treated at moderate temperatures in Utah
trial 2. Degradability exerted opposite effects in the trials; milk yields were higher for the 64% RDP in trial 1 but lower for 61% RDP in trial 2. Cooler ambient temperatures and lower temperature-humidity index in trial 1 than 2 (71 vs. 77 average temperature-humidity index) may have negated the significant protein by heat stress interaction observed previously (15) for 3.5% FCM yield. In trial 2, conditions were more conducive to detection of heat stress; maximum daily temperature-humidity index averaged 80 and 83 for cooled and shaded groups, respectively. Rectal tempera(14). At moderate temperatures (14), milk yields tures (39.2 vs. 39.7'C) and RR (70 vs. 88 followed a much different pattern than they did breathdmin) also were lower for the cooled in the hot environment. Yields were lowest for groups. Cows fed 47% RDP yielded more milk the medium protein treatment of higher RDP, (3.4 kg/d) than did those fed 61% RDP, and the perhaps because of insufficient availability of degradability by cooling interaction also was essential AA. Even though total CP met NRC significant; cooled cows responded more to (30)recommendations, intake of RUP was only lower RDP than did uncooled cows. As in the 88% of the recommended amount. Milk fat studies of Higginbotham et al. (14, 15), neither was depressed by the lower RDP diets (14), RT nor RR were affected by protein degradaand water intakes were increased when higher bility. Intakes of RDP in excess of needs appear to RDP was fed (14, 15). In two subsequent trials (38), the interaction be more related to the negative effect of heat of RDP and cooling of cows during hot sum- stress than the percentage composition of RDP mer weather was studied using a factorial ar- in diets. For example, trials 1 and 2 of the rangement of treatments. All diets averaged study of Taylor et al. (38) and the study of 18.3% CP; trial 1 compared 64 with 55% Higginbotham et al. (15) in a hot environment RDP, but RDP estimates of trial 2 were 61 and showed lowest milk yields on diets exhibiting 47%. As shown in Table 2, evaporative cool- highest RDP intakes in excess of requirements ing increased milk yield in trial 1, but not in (30). The data suggest that overconsumption of Journal of Diury Science Vol. 77, No. 7, 1994
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HUBER ET AL.
TABLE 3. Efect of supplemental protein quality and evaporative cooling on feed intake, milk yield, composition, and efticiency of feed utilization during hot weather (5).
Treatment1 Item
HL-Ec+s LL-Ec+s
Trcatment effect
HL-s
LL-S
SEh4
Rotein
Cooling
-P
kgld Protein %
kg/d
25.5 31.9 30.2 28.9 1.23
24.3 28.1 26.6 25.4 1.11
23.9 28.7 27.2 25.0 1.13
22.7 26.3 24.4 24.0 1.08
.9 .9 1.2 1.1 .07
.18 .01 .01 .06 .24
.IO .02 .03 .03 .35
3.20 1.02
3.28 .91
3.22 .91
3.18 .83
.ll .04
.86 .os
.72 .04
3.09
3.07 .87
3.13 .E9
3.22 .84
.06 .04
.60 .03
.14 .09
.99
IHL = High Lys, LL = low Lys,EC+S = evaporative cooling plus S, and S = shade. Covariant-adjusted least squares means. The S cows were higher than EC+S (P c .05)in mean rectal temperatures (39.1 vs. 38.6'C) and respiration rates (82 VS. 64 breaths/min). Mean mnximum ambient temperature was 35.8'C. and mean temperature-humidity index was 76.6
more than 100 g N/d as RDP lowered yield performance. However, further experimentation is required to quantify such a relationship.
9% higher than those of the cows receiving
shade only. Even though interaction effects were not significant, differences in milk yield between the high and low Lys diets were greater for cows evaporatively cooled and shade (3.8 kg/d) than cows receiving receiving Protoln Quallty shade only (2.4 kg/d). Moreover, cooling efA positive response in milk yield or milk fects were greater with the high Lys than on protein concentration to inclusion of an in- the low Lys diets (3.2 kg/d for high Lys vs. 1.8 creased dietary supply of essential AA (5, 46) kg/d for low Lys). Cows in the shaded environto specific AA, such as Lys (22,34, 35) or Lys ment and fed the high Lys diet produced plus Met (33, has been demonstrated in cooler slightly more milk than those fed low Lys and environments. However, little is known con- receiving evaporative cooling plus shade, sugcerning an interaction of protein quality and gesting that protein quality compensated for heat stress. The study of Chen et al. Q ad- lack of cooling in hot weather. dressed this question by comparing a diet of low Lys content (using corn gluten meal as the principal protein supplement) with one contain- Summary ing 67% higher Lys (from a combination of For maintenance of maximum milk yield soybean, fish, and blood meals). Both diets during periods of heat stress of cows fed diets contained about 43% RDP (30),and the con- typical of those in the southwestern US (which tent of other essential AA was similar (except generally contain 18% or more CP), data sugfor Arg, which was higher in the high Lys gest that RDP should not exceed 61% of total diet). The low Lys diet was 19.2% CP and the dietary CP and that RDP should not exceed high Lys was 18.6% CP. Groups received NRC (30) recommendations by more than 100 evaporative cooling plus shade or shade only g of N/d. Additionally, an important protein in a 2 x 2 factorial arrangement of treatments. quality factor affecting milk yield during heat As shown in Table 3, cows fed the high Lys stress is Lys content of diets. Cows fed 1% diet produced 11% more milk than those on Lys in DM or 241 g/d of dietary Lys produced low Lys, and milk yields of cows evapora- 3 kg more milk than those fed .6% Lys (137 g/ tively cooled and receiving shade were about 4. Journal of Dairy Science Vol. 77, No. 7, 1994
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SYMPOSIUM: NUTRITION AND HEAT STRESS
TABLE 4. Effect of fat supplementation and evaporative cooling on performance of dairy cows in hot summer (3). Tmbnentl Item
MF+S
HP+S
MF+Ec
HF+EC
SEM
DMI, kg/d Milk: kg/d FCM/DMI Milk protein.3 5% Milk fat, % BreWmin Rectal temperature, 'C
26.2 29.5 1.06 2.99 2.93 81.1 39.4
24.7 30.0 1.18 2.95 3.93 85.7 39.4
25.5 31.0 1.15 2.90 3.25 81.2 39.1
24.6 31.7 1.21 2.94 3.13 84.4 39.4
2.6 1.8 .05
.04 .12 5.2 .2
lAdaptcd kom Chan et al. (3). MF+S = Medium fat (4.9%). pen shade; HF+S = high fat (7.7%), pen shade; MF+EC = medium fat, evaporative cooling; and HF+EC = high fat, evaporative cooling. Fat source was prilled fatty acids (Energy Booster 100. furnished by MilL Specialties Co., D u n k , IL). Zcooling effect (P c .08). 3Fat effect (P < .11).
SUPPLEMENTAL FAT AND HEAT STRESS
conducted during hot summer temperatures Supplemental fat for lactating cows has (mean RT of cows was 39.3'C and RR was 83 been a common dietary practice. The possibil- breaWmin) showed only small increases in ity that added fat alleviates heat stress by milk yields (.6 kg) in EC or uncooled cows fed providing nonfermentative energy (26, 40) to 2.5% added prilled fatty acids (Table 4),when cows is of interest. In a study by Moody et al. compared with controls, but EC significantly (29), supplementation of 10% fat ( h m soy- (P < .OS) improved yield (1.6 kg), regardless of bean oil or hydrogenated vegetable fat) in diets fat supplementation. The Arizona studies (3, 4, of thermally stressed cows did not increase 18) suggested that response from added fat is milk yield. Moreover, such high percentages of less for heat-stressed than unstressed cows (Taruminally unprotected fat, particularly from ble 5). Our hypothesis, that added fat would reduce soybean oil, likely would depress fiber digestion if it were included in diets for high yield- heat of fermentation during hot summer teming dairy cows (33). peratures, apparently was erroneous because, More recently, added fat (from whole oil- in support of the study by Moody et al. (29), seeds or commercial fat sources) has been fed neither RT nor RR decreased in cows fed to heat-stressed cows in commercial herds. supplemental fat compared with those of cows Rumen-inert fat, such as calcium soaps of fatty fed no added fat (3, 4). acids, prilled fatty acids, or saturated triglycerThose studies are in apparent contrast with ides (tallow), which minimizes fatty acid inhi- that of Skaar et al. (37), who showed that fat bition of rumen microorganisms (33), has been supplementation tended to increase milk yield added at 2 to 3% of DM to alfalfa-based diets of cows that calved during the warm, but not containing whole cottonseed and increased the cool, season; however, maximum temperamilk yields about 2 kgld (18). However, total tures of the warm months did not exceed 3 5 T , fat content of dietary DM should not exceed 6 and amount of added fat was double (5%) that to 7 % (18, 33). of the Arizona studies. Knapp and Grummer One study at the University of Arizona (3) in heat-stressed cows subjected to maximum (23) also fed 5% prilled fatty acids to groups of daily temperatures of over W C , with mean cows housed in environmental chambers in a RT of 39.6'C and RR of 85 breathdmin, Latin square design with 15-d periods; those showed increased milk yield (1.2 kg) and milk researchers showed a l.l-kg/d nonsignificant fat (.2 percentage units) from diets containing increase in milk yield for cows in the cool alfalfa hay, 10% whole cottonseed, and 2.5% environment fed added fat compared with supplemental fat as prilled fatty acids com- yield of controls, but only a .3-kg/d increase pared with diets without prilled fatty acids. A for cows kept in the warm environment. Howsecond study in Arizona (4)with similar diets ever, 3.5% FCM yields were increased (P < Journal of Dairy Science Vol. 77, No. 7, 1994
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HUBER ET AL.
TABLE 5 . Response to added fat in hot or moderate temperatures (18). Ambient temperature
DMI Reference Control
EB2
-W d ) Hot Hot Moderate Moderate
(4)
(3) (16) (16)
22.9 25.8 24.2 27.2
Milk yield
NEL Intake1
24.0 24.7 25.3 26.8
Control
EB2
-&idd)37.3 42.3 40.6 44.6
41.0 42.1 45.3 46.4
Control
EB2
32.9 30.3 31.6 32.6
34.la 30.9 34.2' 34.33
Milk protein EB2
Control
-W d ) - - (%)
3.14 2.95 3.13 3.03
3.10 2.95 3.01b 3.08
aSignificantly higher than control (P < .lo). bSignificantly lower than control (P < .OS). 1Estimated from M C (30). *EB = Energy Booster 100 (Milk Specialties Co., Dundee, IL).
.OS) because the supplemental prilled fatty acids increased fat content of milk. Further study is needed to delineate clearly the effects of heat stress on response to fat supplementation. These studies should allow for adequate adaptation of cows to hot weather and should establish a response gradient to varying amounts of added fat during heat stress.
fected tolerance of dairy cows to hot environments (16). The principal species from which these cultures were derived are strains of Aspergillus oryzae and Saccharomyces cerevisiae. This discussion evaluates the effects of fungal cultures on body temperatures and FtR as related to heat stress and the effects on milk yield and composition in lactating cows. Rumen changes related to yield responses also are mentioned. The trade name of the A. oryzae cultures that has undergone most investigation is Amaferm@(BioZyme EnFUNGAL CULTURES AND HEAT STRESS terprises, St. Joseph, MO), and those of S. Fungal cultures have been marketed as feed cerevisiae are YeaSaccB (Alltech Biotechnoladditives for livestock and reportedly have af- ogy Center, Nicholasville, KY) and Diamond
TABLE 6. Rectal temperatures (RT) and respiration rates (RR) of cows fed Aspergillus oryme extract (AOE). RT Reference (17)
Trial
Control
AOE
Control
AOE
1 2
39.4 39.8 40.1 39.2 39.0 38.7 39.1 39.1 38.8 38.8 39.3 38.8
38.43 39.3' 39.Y 39.w 38.7 38.5 39.2b 39.1 38.8 38.8 39.3 38.7'
. . . ...
...
67
63
. . .
...
79
82
(25)
...
(10)
1 2 31 1 2
(43)
(21)
0 (13)
RR
...
1 2
...
... ...
...
... I
.
.
70 51
3Mean differences for all measurements lower for AOE than control (P < .05). bMean differences of measurements in early lactation cows higher for AOE than control (P < .OS). CAbout one-half of weekly means lower for AOE than control (P < .05). 'Means of diurnal changes in inner ear for seven cows per treatment. Journal of Dairy Science Vol. 77, No. 7, 1994
...
...
...
...
... ...
74 52
SYMPOSIUM: NUTRITION AND HEAT STRESS
2087
specific influence of fungal metabolites on temperature control centers has been suggested. Meyers (28) reported that a number of compounds elaborated from fungi affect temEffects on UT and RR perature control centers in animals. Typical of Heat-stressed cows in several studies fed such an effect is the decreased body temperaextract of A. oryzae had lower RT, RR, or ture observed in cows fed aflatoxin (Aspergilboth, than companion controls (10, 13, 17, 25), lus f2avus) (27). One might postulate that the enhanced nueven though the magnitude of effects has been variable (Table 6). In other trials, RT of cows trient utilization and increased milk yields that fed A. orywe were not decreased (7, 21) or sometimes occurred when fungal additives tended to be increased (43) compared with were fed would tend to increase, instead of to controls. In one trial with a yeast culture (16), decrease, body temperatures. Such an effect significantly decreased RT were reported for occurred in one study (43) with cows that were cows fed the culture in the early stages of the not subjected to high ambient temperatures. study, but differences did not continue The group of cows in that study were fed A. throughout the entire trial. Because of a lack of oryzae in early lactation and showed signifidata pertaining to heat stress and S. cerevisiae cantly higher milk yields than controls did, but cultures (16), these additives are not be dis- they also had higher RT and RR; however, cussed further. However, many of the effects milk yield and temperatures of the midlactashown for A. oryzae cultures also have been tion group were not affected significantly by demonstrated for yeast cultures (16, 45). In an Arizona study, water intake was the additive. Greatest increases in milk yields slightly higher for cows fed A. oryzae, and no in the early lactation cows fed fungal culture effect on DMI was reported (10). It is not occurred when environmental temperatures likely that the higher water intake would re- were highest (43). Because cows were group duce body temperatures during heat stress, and fed, individual DMI could not be measured, the lack of difference in DMI suggests that but group intakes were the same for both heat of fermentation was not affected. A treatments (21 kg/d).
V Yeast Culture@ (Diamond V Mills, Cedar Rapids, IA).
TABLE 7. Effect of dietary Aspergillus oryzne extract (AOE) on Reference
Trial
(11)
...
(41) (1V (43)
...
1 2 1 2
(23
...
(10)
1 2
(21)
0 (36) (13) Mean
...
1 2
...
... ...
Control
AOE
24.1 24.1 18.5 18.6 30.1 29.0 28.7 22.3 37.3 26.0 30.9 26.6 30.8 39.3 27.6
26.58 25.0 20.4' 18.6 33.6. 27.8 30.2' 23.2 39.83 27.7b 30.82 25.8 30.8 39.6 28.6
-W d ) -
cows
milk yields.
Remarks
(no)
...
34 32 48 48 50 50 205 24 46 100 40 24 12 110
Normal concentrate Low concentrate Started 0 to 60 D M Started 61 to 120 DIM Commercial herd (6 mo) Midlactation Early lactation Complete lactation Early lactation Midlactation Two concentrate levels early to midlactation Midlactation
...
. . .
...
aSignificantly higher than control (f < .05). bHigher in early and late lactation (f < .05). 1Data presented as milk yields and all others as 3.5 or 4% FCM. *Mean of 1.5, 3, and 6 g/d. Journal of Dairy Science Vol. 77, No. 7, 1994
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HUBER ET AL.
TABLE 8. Relationship between dietary Aspergillus oryzoc extract (AOE) and milk composition. ~
~~
~
Millr fat Reference
Trial
Control
AOE
(23
...
(10)
1 2 1 2
3.64 2.97 3.07 3.74 3.97 3.73 3.51 3.22 3.49
3.77 2.93 2.99 3.81 3.90 3.68 3.46 3.36 3.49
0 (21) (36) (13) Mean
...
... ... .
I
.
~
~
~
Control
~
Milk lactose
Milk protein
AOE
Control
AOE
...
...
...
...
3.15 3.02 2.92 3.42
3.20 2.99 2.97 3.24
4.78 4.99 4.83 4.73
5.01 5.03 4.82 4.71
3.21 3.05 3.13
3.18 3.12. 3.12
...
...
... ...
4.94 4.85
...
...
4.95 4.90
aSignificantIy higher than control (P e .05).
As might be surmised, considerably more study is needed to clarify the relationship between dietary fungal additives to rations of dairy cows and their tolerance to heat stress. Further investigation should clearly establish whether a relationship exists between sup plemental dietary fungal extracts and alleviation of heat stress and clarify the mechanism that might elicit such action.
Effecta on Milk Yields and Compoiltlon
In 14 lactation comparisons involving 823 cows, 3 g/d of A. oryzue extract were fed. Mean increases in milk yields of treated cows over controls was 1.0 kg/d (28.6 vs. 27.6 kg/d for A. oryzae vs. control groups) or 4% (Table 7). Cows fed extract were significantly higher in 6 comparisons, slightly higher in 3, and no different or slightly lower in the remaining 5. Data suggest that early lactation cows fed a higher proportion of concentrate responded more to A. oryzae than did those in mid or late lactation. Williams and Newbold (45) observed greater increases in milk yields for cows supplemented with yeast culture when they were fed high than low energy diets. No consistent effect of A. oryzue extract on milk composition was observed (Table 8). Even though Higginbotham et al. (13) reported significantly higher milk protein, magnitude of increase was only .07 percentage units. Based on increases in milk protein and SNF, those researchers (13) suggested that A. oryzae exJournal of Dairy Science Vol. 77, No. 7, 1994
tract usually would be profitable in diets for high producing herds when milk is priced on the basis of protein, SNF, or both. Several ruminal effects of fungal extracts have been associated with improved performance, including increased digestibility of fiber (9, 10, 44, 45) and other dietary components (9, 10) measured in situ (9), in vitro (9), or in vivo (10, 44, 43, particularly on high concentrate diets; greater numbers of cellulolytic bacteria (44);increased rate of turnover of ruminal lactic acid (31, 45); and less diurnal variation in rumen pH, ammonia, and W A , resulting in greater rumen stability (16, 45). A possible relationship among these factors and greater tolerance to heat stress elicited by fungal extracts, if such an effect exists, is yet to be clarified. CONCLUSIONS
The dietary protein fed to cows in hot environments should not exceed the NRC (30) requirement by more than 10 to 15% of total CP and generally would be less than 18% CP. The RDP of high protein diets should not exceed 61% (of CP) or 100 g of N/d. A high Lys content of dietary RUP gave more favorable responses in milk yield of cooled than uncooled cows. In some studies, when 2 to 3% fat was added to diets containing whole cottonseed, cows subjected to hot temperatures increased less in milk yield than did cows in moderate temperatures; contrasting results were shown in other studies. The consistent decrease in milk protein content from sup-
SYMPOSIUM: NUTRITION AND HEAT STRESS
plemental fat does not always occur at hot temperatures. Cultures from A. oryzae (3 g/d) decreased body temperature and increased milk yields in some investigations, but, despite more studies showing a beneficial than an absence of effect by the culture, results have been somewhat inconsistent. REFERENCES 1 Beede, D. K.,and R. J. Collier. 1986. Potential nutritional strategies for intensively managed caale during thermal m s s . J. Anim. Sci. 62543. 2 Chalupa, W., and J. D. Ferguson. 1989. The impact of nutrition on reproduction of cows. Page 59 in Roc. Minnesota Nu&. Conf., Bloomington. 3 Chan, S. C.. J. T. Huber, Z. Wu, K. H. Chen, and J. Simas. 1992. Effect of fat supplementation and protein source on performance of dairy cows in hot environmental temperatures. J. Dairy Sci. 75(Suppl. 1): 175.(Abstr.) 4 Chan, S. H.,J. T. Huber, Z. Wu. J. Simas,K. H. Chen, F. Santos, A. Rodrigues. and J. Varela. 1993. Effects of supplementation of fat and evaporative cooling of dairy cows subjected to hot temperatures. J. Dairy Sci. 76:(Suppl. 1):184.(Abstr.) 5Chen. K. H.,J. T. Huber, C. B. Theurer, D. V. Armstrong, R. Wanderley, J. Sirnas, S. C. Chan. and J. Sullivan. 1993. Effect of supplemental protein quality and evaporative cooling on ladation performance of Holstein cows in hot weather. J. Dairy Sci. 76819. 6Danfaer, A,, 1. Thysen, and V. Ostergiwd. 1980. The effect of the level of dietary protein on milk production. 1. Milk yields, liveweight gain and health. Bent. Statens Husdrbmgsfors. 492. 7Dcnigan. M. E., J. T. Huber, G. Alhadhrami, and A. Al-Dehneh. 1992. Influence of feeding varying levels of AmafermQ on performance of lactating dairy cows. J. Dairy Sci. 75:1616. 8Deres2, F. 1987. Effect of diffmnt cooling systems on concentrations of certain hormones and free fatty acids at varying times during lactation of Holstein cows. Ph.D. Diss., Univ. Arizona, Tucson. Univ. Microfilms Int., Ann Arbor, MI. 9Gomez-Alarcon, R. A., D. Dudas, and J. T. Huber. 1990. Influence of Aspergillus oryzae on mmen and total tract digestion of dietary components. J. Dairy Sci. 73:703. 10Gomez-Alarcon, R. A,, J. T. Huber, G. E. Higginbotham. F. Wiersma, D. Ammon. and B. Taylor. 1991. Influence of feeding an Aspergillus o r y m culture on the milk yields, eating patterns, and body t e m p e m s of lactating cows. J. Anim. Sci. 69:1733. 11 Harris, B., Jr.. H. H. Van Horn, K.E. Manookian, S. P. Marshall, M. J. Taylor, and C. J. Wilcox. 1983. Sugarcane silage, sodium hydroxide and steam pressure-treated sugarcane bagasse, com silage, cottonseed hulls, sodium bicarbonate, and Aspergillus oryzae product in complete rations for lrrctating cows. J. Dairy Sci. 66:1474. 12 Hassan. A., and J. D. Roussel. 1975. Effect of protein concentration in the diet on blood composition and
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29 Moody, E. G., P. J. Van Soest, R. E. McDowell, and G. L. Ford. 1967. Effect of high temperature and dietary fat on performance of lactating cows. J. Dairy Sci. 50:1909. 30 National Research Council. 1989. Nutrient Requirements of Dairy Cattle. 6th rev. d.Nd. Acad. Sci.. Washington, DC. 31 Nisbet, D. J., and S. A. Martin. 1990. Effect of dicarboxylic acids and Aspergillus oryme fermentation extract on lactate uptake by the ruminal bacterium Selenomonas ruminantiurn. Appl. Environ. Microbiol. 56:3515. 32 Oldham, J. D. 1984. Proteinenergy interrelationships in dairy cows. J. Dairy Sci. 67:1090. 33 Palmquist, D. L. 1987. Adding fat to dairy diets. Page 35 in Animal Health and Nutrition. Watt Publ. Co., Mt. Moms, IL. 34Polan. C. E., K. A. Cummins, C. J. Sniffen, T. V. Muscato, I. L. Vicini, B. A. Crooker, J. H. Clark, D. G. Johnson, D. E. Otterby, B. Guillaume, L. D. Muller, G. A. Varga, R. A. Murray, and S. B. PeirccSandner. 1991. Responses of dauy cows to s u p plemental rumen-protected forms of methionine and lysine. J. Dairy Sci. 742997. 35 Schwab, C. G. 1993. Amino acid limitation and flow to duodenum at four stages of laaation. 1. Sequence of lysine and methionine limitation. J. Dairy Sci. 75: 3486. 36Sievert, S. J., and R. D. Shaver. 1992. Carbohydrate and Aspergillus oryzae effects on intake, digestion, and milk production by dairy cows. J. Dairy Sci. 7 6 245. 37Skaar. T.C., R. R. Grummer. M. R. Dentine, and R. H. Stuffacher. 1989. Seasonal effects of prepartum and postpartum fat and niacin feeding on lactation performance and lipid metabolism. J. Dairy Sci. 72: 2028. 38Taylor. R. B., 1. T. Huber, R. A. Gomez-Alarcon, F. Wiersma, and X. Pang. 1991. Influence of protein degradability and evaporative cooling on performance of dairy cows during hot environmental temperatures. J. Dairy Sci. 74:243. 39Tyrrell. H. F., P. W. Moe, and W. P. Flu. 1970. Influence of excess protein intake on energy metabo-
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