Responses of Supplementary Dry, Rumen-Inert Fat Sources in Lactating Dairy Cow Diets

The Professional Animal Scientist 20 (2004):461–469

RDry, Rumen-Inert Responses of Supplementary Fat Sources in EVIEW:

Lactating Dairy Cow Diets J. R. LOFTEN and S. G. CORNELIUS1, PAS Milk Specialties Company, Dundee, IL 60118

Abstract Various fat sources are used to increase energy density of diets for lactating dairy cows. Greater energy density should result in increased production responses if DMI is not decreased. Dry fat products are generally believed to be rumen inert and have beneficial physical properties particularly for on-farm use. Partially hydrogenated tallow (PHT) is limited primarily by its greater melting point, which reduces its digestibility and subsequent energy value to the dairy cow. Free fatty acids (FFA) and Ca salts of fatty acids (CaSFA) now have a considerable body of literature for comparison of effects when fed to lactating dairy cows. Direct comparison studies reviewed, which included these two dry fat sources, found primary differences because of increased DMI and palatability when diets contained FFA. Increased DMI and palatability have positive effects on energy balance, milk production, BW change, and reproductive performance with similar digestibility. Mode of action for reduced DMI when using CaSFA appears to be primarily due to negative effects of gastro-intestinal motility, rumen function, and palatability. Re-

1

To whom correspondence should be addressed: [email protected]

duced DMI impacts the amount and duration of negative energy balance in early lactation, subsequent milk production and reproduction, and economic value. This review found that CaSFA, compared with FFA, reduced DMI, milk protein percentage, and milk production with more variability, but there was a tendency for reduced milk fat percentage and increased BW loss. (Key Words: Free Fatty Acids, Calcium Salts of Fatty Acids, Intake, Production, Reproduction.)

Introduction Fat is extensively used in the diets of lactating dairy cows to increase energy density and milk production. Use of various types of fats in a variety of forage-based diets was extensively reviewed by Smith and Harris (1992). The current review will concentrate on more recent studies with dry, rumen-inert (i.e., not significantly changed in the rumen nor having a significant effect on rumen function) supplemental fat sources and resultant responses in DMI, milk production, milk components, and reproduction. Three main types of rumen-inert fats currently used in lactating dairy cow diets are: partially hydrogenated tallows (PHT), Ca salts of fatty acids (CaSFA), and hydrogenated free fatty

acids (FFA). These fat types were developed to be used in dry form to provide dairy producers with a more functional physical product and to facilitate on-farm handling.

Review and Discussion Types of Rumen-Inert Fats. Partially hydrogenated tallows were the first generation of rumen-inert fats. They are produced by hydrogenating tallow or vegetable fats to increase the melting point of the end product. Tallow or vegetable fats may contain as much as 85% unsaturated fatty acids prior to biohydrogenation and as little as 15% after the hydrogenation process. The iodine value, an indicator of the degree of unsaturation, can vary from 14 to 31 (NRC, 2001). Hydrogenation of tallow and vegetable fats reduces negative effects that fatty acids have on rumen fermentation. However, the same process severely reduces the digestibility of the end product and its potential for value in lactating dairy cow diets. Elliott et al. (1994, 1999) found that resistance to ruminal and small intestinal lipolysis was a major factor contributing to the poor digestibility of highly saturated triglycerides contained in hydrogenated tallow. Calcium salts of fatty acids were the second generation of rumen-inert fats. Palm oil, soybean oil, and other

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fat sources are hydrolyzed and reacted with Ca to form salts, which increases the end product melting point. Fatty acids of Ca salts are stable in the rumen at pH >6.5 (Sukhija and Palmquist, 1990). However, unsaturated fatty acids of CaSFA have been found to be extensively hydrogenated in the rumen by Wu and Palmquist (1991), Ferlay et al. (1993), Enjalbert et al. (1994), and Van Nevel and Demeyer (1996). This indicated that dissociation occurred when the pH dropped below 6.5 after a meal or when the pH was manipulated in vitro. Wu and Palmquist (1991) observed that up to 55% of CaSFA were, in fact, biohydrogenated. Because Hawke and Silcock (1969) found that a free carboxyl group of fatty acids is required for biohydrogenation to occur, CaSFA have to dissociate prior to biohydrogenation. This indicated that CaSFA may not be as rumen inert as previously thought and may be deleterious to rumen fermentation and possibly to DMI. Free fatty acids were the third generation of rumen-inert fats. Rumen-inert FFA are pre-hydrolyzed, mostly hydrogenated, and purified during manufacturing. This form of rumen-inert fat requires no further chemical modification by the cow prior to digestion. Free fatty acids usually have a lesser melting point than PHT or CaSFA and have the tendency to be less soluble in the rumen than fat supplements high in unsaturated fatty acids. Free fatty acids also have little or no negative effects on ruminal fermentation compared with fat sources high in unsaturated fatty acids (Chalupa et al., 1984; Chan et al., 1997). They also have been shown to have minimal or no negative effects on DMI (Davis, 1990; Chilliard, 1993; Allen, 2000). Because of the known and accepted negative effects of PHT on both digestibility and milk production (Elliott et al., 1994, 1999), the remainder of this review will concentrate on direct comparisons of the other two types of rumen-inert fats when used in lactating dairy cow diets.

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Effects of CaSFA and FFA RumenInert Fats on Milk Production and Milk Components. Although rumeninert fats were fed in many studies, only a few have directly compared feeding CaSFA and FFA. Seven trials where these two rumen inert fats were directly compared are summarized in Table 1. Earlier trials used few cows to determine differences among treatments. This might be why differences were not always found although Grummer (1988) and Harvatine and Allen (2002) did observe a significant (P<0.01 and 0.05) decrease in milk protein response for CaSFA compared with FFA. Weighting means by number of cows for each study indicated a trend toward greater daily milk production, fat-corrected milk (FCM) production, milk fat percentage, and milk protein percentage when FFA were compared with CaSFA. Effects of CaSFA and FFA RumenInert Fats on DMI, Fatty Acid Digestibility, and BW Change. Studies directly testing differences between FFA and CaSFA on DMI, fatty acid digestibility, and BW changes are shown in Table 2. Data indicated that there was little difference in digestibility of FA delivered by either CaSFA or FFA. The most pronounced difference between the two rumen-inert fats was effect on DMI. In the two most recent studies conducted by Harvatine and Allen (2002, 2003), a significant (P<0.01 and 0.05) DMI depression occurred when CaSFA were compared with FFA. Data also showed that in five of seven direct study comparisons, FFA resulted in numerically greater DMI than CaSFA. Chilliard (1993) reviewed use of rumen-inert fats and saturated fats in lactating cow diets (Table 3). Data from this review are consistent with data in Table 2 in that DMI was significantly (P<0.01) depressed by the addition of CaSFA to lactating cow diets. Saturated fats also resulted in twice (P<0.01) the amount of 4% FCM production than CaSFA compared with controls. Milk fat percentage was unaffected, but milk protein

percentage was negatively affected, by both saturated fats (P<0.05) and CaSFA (P<0.01), but less with saturated fats. Body weight change was not significantly affected by the addition of saturated fats or CaSFA, but saturated fats had a numerical increase, and CaSFA had a negative numerical influence on BW change. This trend might be expected, as DMI was significantly depressed (P<0.01) with CaSFA in diets. More recently, Allen (2000) extensively reviewed effects of fat supplementation on DMI (Table 4). Regression equations involving 24 studies, where CaSFA were fed and compared with controls, indicated that for every 1% of added CaSFA over the control, a 2.5% DMI depression was found. This finding is reiterated in the NRC requirements (2001). Allen (2000) also reported that in 11 of 24 comparisons, CaSFA significantly depressed DMI. Furthermore, 22 of 24 comparisons were numerically less in DMI when CaSFA were added to diets. Allen also indicated that although energy utilization is more efficient for digested fat than digested carbohydrate, addition of fat to the diet does not always result in increased net energy intake, especially when reduction in DMI occurs. From these published data (Table 2) and critical review papers (Chilliard, 1993; Allen, 2000), it is evident that CaSFA in the diets of lactating dairy cows, even at the low level of 0.23 kg/d, often fed in field practice with commercial herds, can significantly depress DMI. Allen (2000) also noted that no effect of added fatty acids on DMI was observed for hydrogenated fat in 21 comparisons (Table 4). Based on these published journal articles and critical reviews, DMI depression caused by the inclusion of CaSFA in the diets of lactating dairy cows is problematic. It is reasonable to assume that if a nutritionist or a dairy producer decided to replace 0.23 kg of corn or 0.45 Mcal of NEl with 0.23 kg of CaSFA or 1.085 Mcal of NEl, the difference should be 1.085 − 0.45 or 0.635 Mcal. However, when

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TABLE 1. Effects of feeding free fatty acids (FFA) and Ca salts of fatty acids (CaSFA) to lactating dairy cows on milk production, 4% fat-corrected milk (FCM) production, and milk fat and protein percentages. Means are differences between FFA and CaSFA (FFA − CaSFA). Item

Cows, no.

Milk, kg/d

FCM, kg/d

Fat, %

Protein, %

4 4 6 24 5 32 8 83

−2.80 −0.70 −0.90 1.27 1.49 −0.68 2.91 0.22

−2.30 −0.80 −1.20 1.09 2.77 −0.41 2.54 0.31

0.24 −0.07 −0.04 0.02 0.19 0.04 0.03 0.04

0.18** 0.07 0.03 0.04 0.16 0.05* 0.15 0.04

Grummer (1988) Schauff and Clark (1989) Schauff and Clark (1989) Wu et al. (1993) Elliott et al. (1996) Harvatine and Allen (2002) Harvatine and Allen (2003) Weighted mean *Difference within study cited (P<0.05). **Difference within study cited (P<0.01).

a 2.5% reduction in DMI is factored in, net effect is a reduction in total daily NEl intake. Assuming that a cow is consuming 22.7 kg/d of DM and that the diet contained 1.72 Mcal of NEl/kg of DM, total daily NEl intake would be 39 Mcal. If DMI is reduced by 2.5%, or 0.98 Mcal, adding back NEl from CaSFA, or 0.635 Mcal, still leaves a deficit of 0.34 Mcal of NEl. This is consistent with Chilliard’s (1993) review that a negative BW change occurred when CaSFA were in-

cluded in the ration. Financial consequences can be calculated with current and localized data. Mode of Action. Mode of action affecting DMI depression from feeding CaSFA to lactating cows has been identified in three possible areas: palatability and ruminal and gastro-intestinal motility effects. Grummer et al. (1990) determined palatability effects of four different fat products (sodium alginate-encapsulated dry tallow, tallow, FFA, and CaSFA) on two univer-

sity and two commercial dairy farms involving 209 lactating dairy cows. Different fat products were fed alone, top-dressed on grain, or included in the grain mix. In all cases, after 15 min of feeding, FFA were preferred over CaSFA, whether using measurements that were qualitative (scores of 0.33 vs 0.17 for fat fed alone or topdressed; intake scored on the basis of 0 = no intake, 1 = partial intake, or 2 = total intake) or quantitative (13.2 vs 8.2 for fat fed alone or fat mixed

TABLE 2. Effects of feeding free fatty acids (FFA) and Ca salts of fatty acids (CaSFA) to lactating dairy cows on DMI, fatty acid (FA) digestibility, and BW changes. Means are differences between FFA and CaSFA (FFA − CaSFA). Item a

Grummer (1988) Schauff and Clark (1989) Schauff and Clark (1989) Palmquist (1991) Wu et al. (1993) Elliott et al. (1996) Harvatine and Allen (2002) Harvatine and Allen (2003) Weighted means Cows in mean, no. a

Cows, no.

DMI, kg/d

FA digestibility, %

BW change, kg/d

4 4 6 6 24 5 32 8

0.00 0.20 −0.90 NA 1.41 1.50 0.73** 1.35* 0.85 83

−2.50 NA NA −0.80 −0.40 −8.00 NA NA −1.65 39

NAb NA NA NA 0.17 NA 0.31 −0.20 0.17 64

Data corrected for one cow that had a low value as discussed in paper. Free FA and CaSFA comparison was made at 680 g of daily intake of each fat source. Digestibilities were 87.4 and 84.9% for CaSFA and FFA, respectively. b NA = not available in paper. *Difference within study cited (P<0.005). **Difference within study cited (P<0.01).

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TABLE 3. Effects of Ca salts of fatty acids (CaSFA) and saturated fats fed to lactating dairy cows on DMI, 4% fat-corrected milk (FCM), milk fat and protein percentages, and BW change. Means are differences between control and CaSFA or saturated fats (Chilliard, 1993). Item CaSFA Saturated fats

Cows, no.

DMI, kg/d

4% FCM, kg/d

Fat, %

Protein, %

BW change, kg/d

404 170

−0.70** 0.00

0.90* 1.80**

0.05 0.05

−0.10** −0.06*

−0.032 0.055

*Difference among studies summarized (P<0.05). **Difference among studies summarized (P<0.01).

with grain; weighbacks were used to determine intake as a percentage of amount offered that was consumed). In addition, it was observed that cows improved intake of three fat products, but not of CaSFA, when a 7-d period was allowed for adaptation. This observation was important because it indicated a possible inhibitory mechanism beyond palatability or general adaptation that led to continued and prolonged DMI depression. A second possible mode of action regarding DMI depression from use of CaSFA is disruption of ruminal fermentation because of unsaturated fatty acid effects. Although CaSFA were observed to be inert in the rumen in vitro (Sukhija and Palmquist, 1990), Wu and Palmquist (1991) observed that unsaturated 18 carbon fatty acids in CaSFA were 58% biohydrogenated in vivo (Table 5). The researchers stated that biohydrogenation could only occur after dissociation of the Ca salt. Hawke and Silcock (1969) had similar findings and concluded that a free carboxyl group of the fatty acid was required

for biohydrogenation to proceed. Consequently, CaSFA is not inert in the rumen. Therefore, negative effects of unsaturated fatty acids on rumen fermentation are probable. Wu and Palmquist (1991) also concluded that the percentage biohydrogenation increased as level of unsaturation increased (Table 5). Negative effects of unsaturated fatty acids on fiber digestion and milk fat content are well recognized (NRC, 2001). However, because studies show only small differences in fiber digestion and milk fat content when CaSFA are fed to lactating cows, this mode of action is probably not the major factor in DMI depression. Interestingly, significant biohydrogenation of C18:1, C18:2, and C18:3 fatty acids resulted in greater levels of stearic acid reaching the duodenum regardless of whether the dietary source was CaSFA, oil seeds, or forages. Ruminal action largely converts these fatty acids to C18:0. Applying non-ruminant fat digestion principles to ruminants, particularly when downgrading digestibility of stearic vs palmitic or C18 unsaturated fatty acid, is inappropriate and may

TABLE 4. Effects of Ca salts of fatty acids (CaSFA) and hydrogenated fat on DMI, expressed as a percentage of DMI depression for each 1% of added fat to the dietary DM above the control diet (Allen, 2000). Item CaSFA Hydrogenated fat

Means

DMI, % reduction

P

28 29

−2.52 −0.26

<0.0001 0.57

confuse this picture. Most recently, Bauman et al. (2003) noted that digestibility does not differ significantly between C16 and C18 saturated FA, and is less for longer chain saturated fatty acids as compared with polyunsaturated fatty acids (PUFA). Those researchers further noted that differences in digestibility among individual fatty acids contribute very little to the extensive variation (∼60 to 90%) in the digestibility of dietary lipids and that the majority of this variation reflects differences among individual experiments, differences in diets, and to specific feed components. The third possible mode of action regarding DMI depression in cows fed CaSFA is the effect on gastro-intestinal motility. A number of experiments, where 450 g/d of oils containing higher levels of saturated FA or unsaturated FA were abomasally infused into lactating dairy cows, were conducted by Drackley et al. (1992), Christensen et al. (1994), and Bremmer et al. (1998) (Table 6). These data show an average DMI depression of 8% from abomasally infusing PUFA into lactating dairy cows. Reviews of Chilliard (1993) and Allen (2000) estimated a reduction of only 3.5 to 5.0% at this level of DMI. But all of these researchers, except Chilliard (1993), also concluded that DMI depression and subsequent drop in total energy intake were greater than the energy value of infused PUFA. These three studies illustrated the most likely, primary mode of action affecting DMI depression when feeding CaSFA. As the level of PUFA flow increases into the small intestine, there appears to be a mechanism that triggers the satiety center to reduce DMI. Woltman et al. (1995) found that duodenal infusion of oleic acid in rats reduced feed intake and that a portion of the effect was mediated through a gut hormone, cholecystokinin (CCK). Choi and Palmquist (1996) observed that feeding increasing levels of CaSFA to lactating dairy cows decreased DMI linearly and increased concentrations of CCK. Data

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TABLE 5. Biohydrogenation percentage of unsaturated fatty acids in the rumen of cows fed Ca salts of fatty acids (CaSFA) at 3% of the dietary DM (Wu and Palmquist, 1991). Item

0% CaSFA added

3% CaSFA added

44.3 72.9 89.7 67.3

47.1 67.3 81.0 58.3

C18:1 C18:2 C18:3 Total C18

adapted from that study are presented in Table 7. Those researchers concluded that feeding increased amounts of dietary fat (CaSFA) linearly, decreased feed and energy intakes, and linearly increased plasma CCK and pancreatic polypeptide concentrations in lactating cows. They suggested that decreased feed intake in cows fed CaSFA was mediated by increased plasma CCK and pancreatic polypeptide concentrations. Interestingly, even though DMI and NEl intake decreased, milk production and 4% FCM production increased. Logical reason for the increase in production would have been from mobilization of body fat stores. This is supported by data from Chilliard’s review (1993), indicating an average BW loss of 34 g/d per cow for trials with CaSFA (an average from 7 trials with 404 early lactation cows that had reduced DMI of 0.7 kg daily with 0.9 kg more daily milk production compared with non-fat control diets)

vs an average BW gain of 55 g/d per cow for trials with saturated fats (an average from 7 trials with 170 early lactation cows that had no reduction in DMI with 1.8 kg more daily milk production compared with non-fat control diets). The study of Choi and Palmquist (1996) clearly indicated a physiological mechanism associated with DMI reduction because of CaSFA addition to lactating dairy cow diets and is in agreement with Allen’s (2000) review. Drackley et al. (1992) also suggested that degree of unsaturation of fatty acids reaching the small intestine of dairy cows could affect gastro-intestinal motility and reduce DMI. Given that DMI depression experienced when CaSFA are fed is well documented, the dilemma becomes how to meet early lactation, high producing dairy cows’ energy requirements for milk production, reproduction, and BW gain. A recent review (Grummer and Rastanti, 2003) summarized

time required after calving for lactating cows to reach positive energy balance and concluded that total energy intake was the key factor. Energy intake was even more highly correlated than FCM production with days postcalving before cows reached positive energy balance. Energy intake is the product of energy density in the diet and DMI. If an increase in energy density is accompanied by a reduction in DMI, the level of energy intake is limited, which in turn limits the return to positive energy balance and or reduces production response. Effects of Rumen-Inert Fats on Reproduction. Influence of rumen-inert fat supplements on reproduction is not well understood and is a current topic among nutritionists, reproductive physiologists, and veterinarians. Research when feeding FFA (Ferguson et al., 1990) and CaSFA (Sklan et al., 1991) showed significant positive effects on services per conception, pregnancy rates, and days open. However, others have observed a combination of negative results, positive results, and some contradictory results (Sklan et al., 1994; Moallem et al., 1997; Garcia-Bojalil et al., 1998; and Moallem et al., 1999). A review of nine studies with 701 cows (Table 8) found very few significant differences caused by high variability in data. Thus, reproductive parameters require more observations to make meaningful statistical comparisons. These data indicated few significant differences (P<0.05) be-

TABLE 6. Effects of abomasally infusing daily into lactating dairy cows 450 g of either polyunsaturated (PUFA) or saturated fatty acids (SFA) on DMI, total fatty acid digestibility percentage (TFADIG%), and DE intake (DEI).

Item a

Drackley et al. (1992) Christensen et al. (1994)b Bremmer et al. (1998) Weighted means a

DMI, kg/d

TFADIG %

Control

SFA

PUFA

Control

SFA

PUFA

Control

SFA

PUFA

4 5 6 15

24.5* 22.9 22.8x 23.3

25.1* 21.3 21.6x 22.4

22.4* 20.2 19.9y 20.7

69.60 81.00 73.00 74.76

70.50 76.90 75.20 74.51

77.80 76.00 78.20 77.36

66.50* 67.10* 65.30x 66.22

72.10* 68.70* 61.20x 66.61

63.90* 62.00* 55.90y 60.07

DMI linear contrast (P<0.02); DEI linear contrast (P<0.01). DEI orthogonal contrast of SFA vs PUFA (P<0.05). x,y Means with different superscripts within DMI or DEI differ (P<0.05). b

DEI, Mcal/d

Cows, no.

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TABLE 7. Effects of Ca salts of fatty acids (CaSFA) on DMI, milk production, 4% fat-corrected milk (FCM) production, and milk fat and protein percentages of lactating dairy cows (Choi and Palmquist, 1996). CaSFA in DMI Item Intake DMI, kg/d NEl, MJ/d Yield Milk, kg/d 4% FCM, kg/d Milk fat, % Milk protein, %

0%

3%

6%

9%

23.9 152

21.7 153

20.3 142

19.8 139

31.9 28.5 3.30 3.10

32.2 29.5 3.15 2.97

tween treatments for either first-service conception rate or pregnancy rate. Slight improvement in first-service conception rate appeared from CaSFA treatments, but a larger numerical reduction was noted in overall pregnancy rate when CaSFA were added to diets of high producing early lactation cows in these studies. There are fewer published studies regarding the effects of added FFA to control diets on reproductive measurements. Ferguson et al. (1990) compared FFA added at 500 g/d to control diets fed in three Pennsylvania

32.5 29.6 3.34 2.96

29.9 26.8 3.41 2.99

herds and one Israeli herd (Table 9). Researchers generally concluded that FFA addition to diets benefited reproduction by minimizing BW loss and hastening BW gain postpartum. Both of these effects have been shown to benefit conception rate (Butler et al., 1981; Lopez-Gatius et al., 2003). Most recently, Frajblat and Butler (2003) reported reproductive responses when 81 dry cows were fed daily either 200 g FFA or no FFA during the last 21 d of the dry period (i.e., close-up cows). Cows were bred beginning at d 55 postpartum and

were bred by signs of behavioral estrus until d 220 postpartum (Table 10). Frajblat and Butler (2003) observed close-up cows receiving 200 g/ d of FFA had greater (P<0.05) pregnancy and conception rates and fewer (P<0.05) days open. Additionally, cows exhibiting their first ovulation at less than 50 d postpartum were observed to be nearly twice as likely to become pregnant prior to 220 d postpartum than cows having their first ovulation at >50 d postpartum. Frajblat and Butler (2003) also observed that cows fed 200 g/d FFA in the close-up period, and that had an ovulation prior to 50 d postpartum, were even more likely to be pregnant at 220 d postpartum. Furthermore, cows losing less body condition score in early lactation were observed to have more ovulations prior to 50 d in milk (Table 11). These results are the first to show a benefit when fat was fed to dry cows. A possible mechanism for this response may be derived from work of Moallem et al. (1999), who observed that oleic and linoleic unsaturated fatty acids were found in lesser concentrations in nonesterified fatty acid fraction of follicular fluid in estradiol-active vs estradiol-inactive or estradiol-less active follicles. Estradiol-active or -inactive

TABLE 8. Effects of Ca salts of fatty acids (CaSFA) in diets compared with controls on first-service conception rate and pregnancy rate of lactating dairy cows.

Item Schneider et al. (1988) Sklan et al. (1989) Carroll et al. (1990) Sklan et al. (1991) Holter et al. (1992) Lucy et al. (1992) Sklan et al. (1994) Moallem et al. (1997) Garcia-Bojalil et al. (1998) Weighted means a

Cows, no. 108 108 46 126 58 40 122 48 45

NA = not available in paper. *Difference within study cited (P<0.05).

Control First service conception rate, %

CaSFA First service conception rate, %

Control pregnancy rate, %

CaSFA pregnancy rate, %

43 28 33 42 35 44 55 45 33 41

60 44 75 39 44 12* 33* 45 46 44

NAa NA 57 82 83 NA 75 82 52 75

NA NA 30 62* 79 NA 61 73 86* 64

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TABLE 9. Effects of mostly saturated dietary free fatty acids (FFA) in diets on reproductive parameters of lactating dairy cows and body weight (BW) change per intervals of days in milk (DIM) (Ferguson et al., 1990). Item

Control

500 g/d of FFA

P

Cows, no. Pregnant cows, no. Services/conception, pregnant cows Services/conception, all cows First service conception rate, % Overall conception rate, % Overall pregnancy rate, % Days open BW change, kg/DIM 30 to 59 d 60 to 89 d 90 to 150 d

138 119 1.91 1.96 42.6 40.7 86.2 96.2

115 107 1.59 1.57 59.1 59.3 93.0 91.9

<0.05 <0.05 <0.005 <0.005 <0.08 >0.10

−30.3 −16.0 +7.3

−24.8 −9.5 +20.1

TABLE 10. Effects of prepartum free fatty acids (FFA) fed to dry cows during last 3 wk of gestation on reproductive measures (Frajblat and Butler, 2003). Item Pregnancy rate, % Days open Conception rate, %

No FFA

200 g/d of FFA

58* 141* 26*

86* 110* 40*

*Difference between treatments (P<0.05).

follicles were determined by follicular size. A significant negative correlation coefficient between these two unsaturated fatty acids and the estradiol concentration in follicular fluid suggested that preovulatory growth was accompanied by a decrease in these two un-

saturated fatty acids and an increase in the proportion of the saturated palmitic FA. The saturated stearic fatty acid was numerically elevated by nearly 14% at the same time in nonesterified fatty acid fraction of follicular fluid of estradiol-active follicles vs

TABLE 11. Effects of free fatty acids (FFA) fed to prepartum cows on early ovulation and pregnancy rates during subsequent lactation (Frajblat and Butler, 2003).

Item Control 200 g/d of FFA

Observed cows pregnant and with first ovulation <50 d postpartum, no.

Cows pregnant and with first ovulation <50 d postpartum, %

P

14 of 21 23 of 23

66.6 100

<0.05

the -inactive or -less active follicles. Stearic acid in the phospholipid fraction of follicular fluid of estradiol-active follicles was significantly greater (P<0.05) than the less active or inactive follicles (26.4% vs 23.6% of phospholipids). Free fatty acids fed in this study contained 47% stearic acid, 37% palmitic acid, and only 15% oleic acid. This research may explain why CaSFA, which are greater in oleic and linoleic fatty acids compared with FFA, have more variable results in reproductive trials. Another potential factor is the Grummer and Rastanti (2003). In their study, NEl intake is more highly correlated (r = 0.58, P< 0.0001) with time required to reach energy balance; thus, cows may be in negative energy balance longer and lose more body condition when fed CaSFA because of DMI depression. Frajblat and Butler (2003) concluded that cows losing less body condition had more ovulations prior to 50 d in milk and cows with an ovulation before 50 d in milk were 2.4 times more likely to become pregnant before 220 d in milk.

Implications Dry fat products are thought to be rumen inert and have beneficial physical properties for on-farm use. Partially hydrogenated tallow is limited primarily by its greater melting point, which reduces its digestibility and subsequent energy value. Free fatty acids and CaSFA now have a considerable body of literature for comparison of effects when fed to lactating dairy cows. Direct comparison studies of these two dry fat sources found primary differences caused by greater DMI and palatability when rations contained FFA. This has corresponding positive effects on energy balance, milk production, BW change, and reproductive performance with similar digestibility. Mode of action for reduced DMI when using CaSFA appears primarily caused by negative effects of gastro-intestinal motility, rumen function, and palatability. Reduced DMI impacts amount and

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duration of negative energy balance in early lactation, subsequent milk production and reproduction, and economic value.

Drackley, J. K., T. H. Klusmeyer, A. M. Trusk, and J. H. Clark. 1992. Infusion of long-chain fatty acids varying in saturation and chain length into the abomasum of lactating dairy cows. J. Dairy Sci. 75:1517. Elliott, J. K., J. K. Drackley, A. D. Beaulieu, C. G. Aldrich, and N. R. Merchen. 1999. Effects of saturation and esterification of fat sources on site and extent of digestion in steers: Digestion of fatty acids, triglycerides, and energy. J. Anim Sci. 77:1919.

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