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Effect of Source and Amount of Supplemental Fat on Lactation and Digestion in Cows1
Effect of Source and Amount of Supplemental Fat on Lactation and Digestion in Cows1 2. WU, J. T. HUBER,, S. C. CHAN, J. M. SIMAS, K. H. CHEN J. 0. VARELA, F. SANTOS, C. FONTES, JR., and P. YU Department of Animal Sciences University of Arizona Tucson 85721 ABSTRACT
= safflower oil, WCS = whole cottonseed, WCSPT = WCS plus 2.2% prilled tallow fatty acids, WCSPT+ = WCS plus 4.4% prilled tallow fatty acids, WCSSO = WCS plus 2.2% safflower oil.
Thirty Holstein cows averaging 50 DIM were assigned to five dietary treatments for 75 d to determine the effects of source and amount of supplemental fat on milk yield, milk composition, and nutrient digestibilities. Diets were 1) control, 2) diet 1 plus 12% whole cottonseed, 3) diet 2 plus 2.2% safflower oil, 4) diet 2 plus 2.2% prilled tallow fatty acids, and 5) diet 2 plus 4.4% prilled tallow fatty acids. Milk yield was increased an average of 2.1 kg/d by addition of 2.2% prilled tallow fatty acids or safflower oil to the diet (7% fatty acids) containing 12% whole cottonseed. However, when fatty acids were increased to 9.1% with additional prilled tallow fatty acids, milk yield, DMI, and fatty acid digestibility decreased. Whole cottonseed alone and in combination with all fat additions decreased milk protein concentrations. Safflower oil increased CI?:~, C18:l,and C18:2 fatty acids in mlk. Digestibilities of OM, NDF, and ADF were not affected by diet. Supplementation of a saturated or unsaturated fat source to increase fatty acid content to 7.0% of dietary DM increased milk yield, but a further increase in fat to 9.1% with the saturated source appeared excessive for cows yielding 30 to 35 kg/ d of milk. (Key words: fat, lactation; digestion, cows)
INTRODUCTION
Abbreviation key: EE = ether extract, FA = fatty acids, FT = prilled tallow fatty acids, SO
Received November 29, 1993. Accepted February 18, 1994. 'This research was partially supported by Milk Specialties Co.,Dundee, IL. 2Reprints.
1994 J Dairy Sci 77:1644-1651
In a previous study (29), addition of fat from prilled tallow fatty acids (PT; Energy Booster@; Milk Specialties Co., Dundee. IL), Ca salts of palm fatty acids, or tallow to a diet containing 7.2% whole cottonseed (WCS) to increase fat content from 4.2 to 6.7% resulted in average increases of 2.1 kg/d in milk yield. Digestibilities of dietary nutrients, except for fatty acids (FA), were unaffected by addition of fat. In other studies, ruminal fermentation characteristics and nutrient digestibilities were unchanged when 2.2% tallow was added to diets containing 10% whole soybeans (24) or high oil corn (10) for lactating cows, which suggests that tallow or ruminally resistant fats can be combined with oilseeds to maximize dietary fat for lactating cows without depressing digestibilities of other nutrients. Addition of fat to diets for lactating cows increases energy intake in support of higher milk yields, provided it does not reduce DMI. The currently recommended maximum fat concentration is 6 to 7% of dietary DM (18), but this limit was established for cows yielding 20 to 30 kg/d of milk and was based on inhibition of ruminal metabolism and decreased efficiency of milk yield by higher fat. As yield potential of cows has increased and ruminally resistant fats have become available, maximum dietary fat should be reconsidered. Coppock and Wilks (8) suggested that dairy producers include oilseeds in the diet of cows to increase FA from 3% of dietary DM (approximate amount in common lactation diets) to 6%, and to add 3% more FA from ruminally resistant sources for a total of about 9%. However, increased dietary FA from 6.1 to 8.6% of diets
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SUPPLEMENTATION OF FAT FOR DAIRY COWS
for cows yielding approximately 40 kg/d of milk did not enhance milk yield, but reduced DMI (10). Dietary FA at 9% may result in reduced FA digestibility (14) because of limited biliary and pancreatic secretions into the small intestine, although these were not detennined in the study of Elliott et al. (10). The objective of this study was to determine the effects on milk yield and composition and on digestion of nutrients of increasing dietary fat from 3 to 7% by using a combination of WCS and a ruminally resistant fat (a) or safflower oil PO), which is highly unsaturated and not resistant to ruminal hydrolysis. Response of cows to a further increase in dietary fat from 7 to 9% with PT also was tested.
TABLE 1. Ingredient and nutrient composition of diets varying in fat content for lactating cows. Diet Item Ingredient, 5% of DM Alfalfa hay Whok cottonseed Cottonseed hulls
corn Wheat mill run
Barley cononseed meal Minerals and vitamins2 Molasses
Urea Composition of DM NEL,~Mcavkg CP, %
ADF, % NDF, %
MATERIALS AND METHODS
Holstein cows (n = 30; 25 multiparous) averaging 50 DIM were fed the normal herd diet (containing 38% alfalfa hay, 12% WCS, 4% cottonseed hulls, and 46% concentrate mix) during a 14-d pretreatment period. Based on pretreatment milk yield, DIM, and parity, cows were assigned to six outcome groups and allotted randomly to five dietary treatments for 75 d. Estimated content of ether extract @E) (18) of the basal diet (control) was 3.1% (Table 1). Other dietary treatments were basal diet plus 12% WCS (5.2% EE), WCS plus 2.2% SO (wcsso; 7.4% EE), wcs plus 2.2% PT (wCSPT; 7.4% EE), or WCS plus 4.4% PT (WCSPT+; 9.6% EE). Diets containing 7.4% EE were in accordance with recommendations (18) for added fat, but 9.6% EE was projected as a high amount; similar additions of SO and PT permitted comparison of the two supplements. The SO and PT were added to the WCS diet, so all other ingredients were diluted by added fat. To prepare the WCSSO diet, SO first was mixed with the concentrate portion of T M R to enhance handling. Cows were housed in group pens of 10 each, offered diets once daily, and milked at 0800, 1600, and 2400 h. Amounts of TMR offered to individual cows were adjusted daily for 10% orts as measured with Calm gates (American Calan Inc., Northwood, NH). Cows were weighed after the 1600-h milking for 2 consecutive d at the beginning and end of
Control
WCS'
43.0
38.0 12.0 4.0 22.0 9.9 6.9 2.7 2.1 1.8
...
6.5 24.0 10.9 7.7 3.0 2.3 2.0 .6 1.51 18.6 20.8 31.1
.5
1.64 18.9 21.6 32.5
'A diet containing whole cottonseed. Additionally,
three more diets were formed by addition of prilled tallow fatty acids at 2.2 or 4.4%or d o w e r oil at 2.2% to the
wcs
diet. 2A commercial supplement containing 33.3% calcium carbonate., 38.7% dicalcium phosphate. 17.3% tracemineralized salts, and 10.7%vitamins A, Dj. and E ( ~ c u latcd to furnish 50,000 IU of vitamin A, 5,000 IU of vitamin D3. and 250 mg of vitamin Wd per cow). 3Estimated from NRC (18).
treatment. Daily BW change during treatment was calculated for statistical analysis. From d 48 to 62 of treatment, T M R were mixed with .l% Cr2O3 as a digesta marker to measure nutrient digestibilities. The Cr2O3 (1.5 kg) was first mixed with concentrate (22.5 kg) using a cement mixer, and the mixture then was blended into the TMR (1476 kg) to obtain the correct concentration of Cr. From d 58 to 62 of treatment, T M R and orts were sampled once daily, and feces were sampled twice daily immediately after the milkings at 0800 and 1600 h. Samples were composited for the 5-d collection, and nutrient digestibilities were determined from ratios of Cr concentrations in diets consumed to concentrations in feces. For the remainder of the experiment (other than d 58 to 62), weekly samples of TMR and orts were composited by treatment for nutrient analysis. Samples of T M R and orts were air dried, and fecal samples were dried in an oven at J o d of Dairy Science Vol. 77, No. 6, 1994
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WU ET AL.
TABLE 2. Fatty acid composition of whole cottonseed, prilled tallow fatty acids, and safflower oil.
was according to the method of Fenton and Fenton (11). Milk samples were collected weekly from Prilled tallow Safflower Fatty Whole acid cottonseed fatty acids1 oil2 three consecutive milkings from the initial week of pretreatment to the end of treatment, (dl00 g of methyl esters) and daily composites were analyzed at the DHI c14:0 1 .o 3.7 .I laboratory (Phoenix, AZ) for fat, protein, lac41.9 8.4 c16:0 26.3 40.0 2.6 3.1 c18:0 tose, and total solids according to infrared 3.1 16.3 c18:l 18.3 procedures; SCC were determined using a .5 69.9 c18:2 46.9 white blood cell counting method (Foss 360; 4.4 Other FA 10.8 2.7 Foss Technology, Eden Prairie, MN); SNF was 1Obtained from Milk Specialties Co. (Dundee, E,). calculated by difference between total solids Trade name, Energy Booster@. and fat. Milk samples from wk 8 of treatment 2Obtained from Chicasha Cotton Oil Co. (Casa Grande, also were analyzed for FA as methyl esters a). (27) using the GLC. Data were subjected to ANOVA by the general linear models procedure of SAS (23) for randomized block designs. The data from 50°C for 48 h. All samples were ground in a the 14-d pretreatment period were used for cyclone mill (Udy Co., Fort Collins, CO) to covariate adjustment of DMI, milk yield, and pass a 1-mm screen and analyzed for DM milk composition. Preplanned contrasts were (100°C for 24 h), OM by the method of AOAC control versus WCS, WCSSO versus WCSPT, (2), CP by AOAC (2) using a digestion system control plus WCS versus WCSSO plus (TecatorB; Hoganas, Sweden) and N auto- WCSPT, and WCSPT versus WCSPT+. Siganalyzer (Bran and Luebbe, Analyzing Tech- nificance was declared at P < .10 unless othernologies, Elmsford, NY), and ADF and NDF wise indicated. according to the methods of Robertson and Van Soest (22). Long-chain FA in fat sources RESULTS AND DISCUSSION and TMR were analyzed according to the method described by Abu-Salah et al. (1). Total Table 2 shows the quantity of the major FA FA in feces were determined by the method of in fat supplements used in the study. The SO Sukhija and Palmquist (27) using GLC (model contained a large amount of c18:2 (70%); PT 3300; Varian Associates, Inc., Walnut Creek, was high in c16:O and c18:O; and WCS fat was CA). Analysis of Cr in TMR, orts, and feces intermediate in c16:O and c l 8 : 1 , but relatively
-
-
TABLE 3. Fatty acid (methyl esters) content and composition of diets (DM basis) for lactating cows. Diet1 Fattv acid Content, % of DM c140 c16:0 c18:0 c18:l c18:2
c18:3
c20:4 Other
wcs
C 3.2
4.9
.I
.8 23.3 3.2 16.8 42.2 5.0 1.7 7.0
20.8 4.5 16.2 38.0 8.3 2.7 8.8
wcsso
WCSPT
7.0 6.9 (g/lOO g of methyl esters) .7 1.5 19.1 26.9 4.0 18.8 16.3 10.9 48.0 25.3 3.4 4.1 1.1 1.3 7.4 11.2
wcsPT+ 9.1 2.0 32.2 26.1 12.0 16.9 2.4 1.1 7.3
'Dietary treatments: C = control, WCS = 12% whole cottonseed, WCSSO = WCS plus 2.2%safflower oil, WCSPT = WCS plus 2.2% prilled tallow fatty acids, and WCSPT+ = WCS plus 4.4% prilled tallow fatly acids. Journal of Dairy Science Vol. 77, No. 6, 1994
SUPPLEMENTATION OF FAT FOR DAIRY COWS
high in c18:2. Linoleic acid (c18:2) was more inhibitory to ruminal microbes than were c16:O and C18:O (6). Long-chain FA in all diets (Table 3) were lower than projected from the EE content of feeds (18), but EE includes lipids and glycerol that are not FA. However, FA differences among diets were as planned. The FA content in diets showed high c18:2 in WCSSO, and high c16:O and c18:O in WCSPT and WCSPT+, reflecting the FA composition of the fat supplements. Milk yield of cows did not differ between the control and WCS diets (Table 4). Whole cottonseed, an economical feedstuff in some regions, is high in fiber and energy and can be used as a substitute for forages and concentrates, as well as a supplemental fat source. In support of these findings, WCS failed to increase milk yields from those of other studies (9, 16, 26). Compared with the control and WCS diets, WCSSO and WCSPT increased (P < .05) milk yield an average of 2.1 kg/d; no difference was found between WCSSO and WCSPT. In a previous study (29), addition of 2.2% tallow, PT, or Ca salts of palm FA increased milk yield similarly. In the present study, alleged ruminal resistance of PT did not increase milk yield compared with that of SO when both were added at 2.2% of the diet. Milk yields were not significantly different for WCSPT (34.3 kdd) and WCSpT+ (33.0 kg/ d), but DMI was lower for WCSPT+, 26.8 and 24.1 kg/d for the respective diets. Other diets (control, WCS, and WCSSO) were somewhat higher in DMI than WCSPT+ and did not T differ from WCSPT. Similarly, addition of E to diets at 2.5% of DM did not adversely affect DMI in other studies (7, 29). The decrease in DMI with 4.4% PT was probably because of excessive fat supplementation (9.1% total FA) and not because of the fat source. Lack of increased milk yield with similarly high intakes of dietary fat also was shown by Ferguson et al. (12) for cows yielding 19 kg/d of milk, and by Elliott et al. (10) and Holter et al. (13) for cows yielding up to 40 kg/d of milk. Diets did not affect BW gain of cows, even though cows fed WCSPT+ tended to gain less than other groups. Percentage of milk protein was lower (P c .04)for cows fed WCS than for controls (Table
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4), but did not differ significantly in other
contrasts. However, milk protein generally was decreased for all diets with supplemental fat. Yield of milk protein was not altered by amount of dietary fat, as demonstrated in other studies (25, 29). Restriction in AA availability for milk protein synthesis appears to be a likely hypothesis (4) for explaining the decrease in milk protein percentage with added fat. Plasma AA concentrations and mammary blood flows per unit of milk volume were lower (3), but efficiency of utilization of AA in the mammary gland was higher (3,5),for cows receiving supplemental fat than for control cows; this result suggested that decreases in milk protein concentration with added fat may result from an insufficient supply of AA to the mammary gland to sustain a greater milk protein synthesis needed to accompany the increased milk yields stimulated by fat supplementation. Percentages of fat, lactose, and SNF of milk and SCC in milk were not affected by treatment, but yields of milk and 3.5% FCM were higher for WCSSO and WSCPT than for control and WCS. Fat percentage for WCSSO was somewhat lower than for WCSPT. Fat sources high in c18:2 decrease milk fat concentrations (15, 17) because of an inhibition of ruminal cellulolytic bacteria by c18:2 and inhibition of FA synthesis in the mammary gland (19). The inhibition of mammary FA synthesis may be via rrans-C18,1 (28), which originates mainly from ruminal biohydrogenation of c18:2, when this FA is fed in large amounts (30). However, concentrations of t?-ans-Clg:lin milk fat were not measured. Composition of milk FA is shown in Table 5. Because FA were converted to methyl esters for analysis, and not to butyl esters, the shortchain FA, especially C ~ Omight , have been underestimated, which would lead to overestimates of the percentages of long-chain FA. Percentages of c18:O. c18:17 and c18:2 FA in milk fat increased, but C40 to C14:o decreased, when WCS, PT, or SO was fed. Milk from cows fed the SO diet only had 18% of its FA as C4:o to C14:0, compared with 33% for the controls, suggesting that SO may have compromised de novo fatty acid synthesis in the mammary gland through a decrease in ruminal acetate production (6). Addition of 4.4% compared with 2.2% PT resulted in slight increases Journal of Dairy Science Vol. 77, No. 6, 1994
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8
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SUPPLEMENTATION OF FAT FOR DAIRY COWS
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WU ET A L
TABLE 6. Apparent total tract digestibilities of components in diets supplemented with different sources and amounts of fat for lactating cows. Contrast
c vs. Item
C
WCS WCSSO WCSPT WCSPT+ SEM WCS
OM
53 58 45 45
56 59 45 47
76
74
CP ADF NDF Fatty acid
P <
46
(96) 58 64 46 45
57 69 47 48
2 2 5 4
74
76
69
4
56 60 45
WCSSO vs. c + wcs vs. WCSPT vs. WCSPT WCSSO + WCSPTWCSPT+
.13 NS NS
NS NS NS NS
.12 NS NS NS
NSZ .02 NS NS
NS
NS
NS
NS
NS
'Dietary treatments: C = control, WCS = 12% whole cottonseed, WCSSO = WCS plus 2.2% safflower oil, WCSFT = WCS plus 2.2% prilled tallow fatty acids, and WCSPT+ = WCS plus 4.4% prilled tallow fatty acids. ZP > .15.
in c16:O and c18:~, but decreases in C14:o and C18:2, which could not be attributed entirely to the FA of FT. At the same percentage of supplementation and compared with PT, SO increased the percentages of CIS:^, c18:2, and C18:3, and decreased percentages of C p o , C149, and c16:0, which are mostly synthesized in the mammary gland, suggesting some inhibition of FA synthesis by SO. Digestibilities of OM were relatively low for all diets (Table 6), reflecting the high DMI, which averaged 4.6% of BW for all treatments. Digestibilities of DMI and OM were similar to those for diets with alfalfa hay, cottonseed, and cottonseed hulls as fiber sources observed in other studies (21, 29). The OM digestibility for the control diet tended to be lower (P < .13) than that for WCS as well as for other diets, partly because of lower CP digestibility. Supplemental fat enhanced CP digestibility and was associated with increased ruminal N H 3 losses (20). Digestibilities of ADF and NDF were unaffected by amount or source of dietary fat. The lower DMI for WCSP"+ might favor increased digestion of ADF and NDF because of longer retention time in the rumen. Although FA digestibilities were quite variable (Table 6), they averaged 74.8% after the value for WCSPT+ was excluded and approximated those (76.4%) determined previously using similar fat percentages (29). Digestibility of FA for WCSFT+ tended to be lowest, suggesting that increased FA content from 7.0 to 9.1% of the diet decreased FA digestibility. Jointly Journal of Dairy Science Vol. 77, No. 6, 1994
with the decreased DMI, the lowered FA digestibility might have been responsible for the tendency of lower milk yield for WCSPT+ than for WCSPT. CONCLUSIONS
Milk yield of cows was increased by WCSPT or WCSSO diets, which increased dietary FA to 7.0% of DM, but numerically decreased when PT was fed to increase dietary FA from 7.0 to 9.1%. No difference in milk yield of cows was found between the WCSPT and WCSSO diets. The WCSFT+ diet decreased DMI and tended to decrease FA digestibility. Addition of fat did not affect apparent digestibilities of OM, ADF, or NDF. The WCSSO diet increased the percentages of C18:1, C18:2, and C18:3 FA in milk. Ruminal saturation of FA from the WCSSO diet might have precluded significant decreases in milk fat percentage and digestion of nutrients. Fat at 9.1% of dietary DM appeared to be excessive for cows yielding 30 to 40 kg/d of milk. ACKNOWLEDGMENTS
The authors greatly appreciate the expertise in analyzing samples of M. Francolin, K. Y. Lei, and F. Rosenstein. REFERENCES
1 Abu-Salah, K. M., A. A. AI-Othman, and K. Y. Lei. 1992. Lipid composition and fluidity of the erythro-
SUPPLEMENTATION OF FAT FOR DAIRY COWS cyte membrane in copper-deficient rats. Br. J. Nutr. 68 :435. 2Association of Ofticial Analytical Chemists. 1980. Official Methods of Analysis. 12th ed. AOAC, Washington, DC. 3 Cant, J. P., E. J. DePeters, and R. L. Baldwin. 1991. Effect of dietary fat and postruminal casein administration on milk composition of lactating dairy cows. J. Dairy Sci. 74:211. 4Cant. J. P.. E. J. DePeters, and R. L. Baldwin. 1993. Mammary uptake of energy metabolites in dairy cows fed fat and its relationship to milk protein depression. J. Dairy Sci. 76:2254. SCasper, D. P., D. J. Schingoethe, and W. A. Eisenbeisz. 1990. Response of early lactation cows to diets that vary in ruminal degmdability of carbohydrates and amount of fat. J. Dairy Sci. 73:425. 6Chalupa, W., B. Rickabaugh. D. S. Kronfeld, and D. Sklan. 1964. Rumen fermentation in vitro as influenced by long-chain fatry acids. J. Dairy Sci. 67: 1439. 7Chan. S. C., J. T. Huber, Z. Wu, K. H. Chen. and J. Simas. 1992. Effect of fat supplementation and protein source on performance of dauy cows in hot environmental temperatures. J. Dairy Sci. 75(Suppl. I): 175.(Abstr.) 8 Coppock, C. E., and D. L. Wilks. 1991. Supplemental fat in high-energy rations for lactating cows: effects on intake, digestion, milk yield, and composition. J. Anim. Sci. 693826. 9DePeters, E. J., S. J. Taylor, A. A. Franke, and A. Aguim. 1985. Effects of feeding whole cottonseed on composition of milk. 1. Dairy Sci. 68:697. lOElliott, J. P., J. K. Drackley, D. J. Schauff, and E. H. Jaster. 1993. Diets containing high oil com and tallow for dairy cows during early lactation. J. Dairy Sci. 76: 775. 11 Fenton, T. W., and M. Fenton. 1979. An improved procedure for determination of chromic oxide in feed and feces. Can. J. Anim. Sci. 59:631. 12Ferguson, J. D., D. Sklan, W. V. Chalupa, and D. S. Kronfeld. 1990. Effects of hard fats on in vitro and in vivo rumen fermentation, milk production, and reproduction in dairy cows. J. Dairy Sci. 73:2864. 13 Holter, J. B., H. H. Hayes, W. E. Urban, Jr., and A. H. Duthie. 1992. Energy balance and lactation response in Holstein cows supplemented with cottonseed with or without calcium soap. J. Dairy Sci. 75:1480. 14 Khorasani, G. R., G. de Boer, P. H. Robinson, and J. J. Kennelly. 1992. Effect of canola fat on ruminal and total tract digestion, plasma hormones, and metabolites in lactating dairy cows. J. Dairy Sci. 75:492. 15 Kim,Y.K., D. J. Schingoethe, D. P. Casper, and F.C. Ludens. 1993. Supplemental dietary fat from extruded soybeans and calcium soaps of fatty acids for lactating dairy cows. J. Dairy Sci. 76:197.
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16Lanham, J. K.,C. E. Coppock, K. N. Brooks, D. L. W&, and J. L. Homer. 1992. Effects of whole cottonseed or niacin or both on casein synthesis by lactating Holstein cows. J. Dairy Sci. 75184. 17Middaugh. R. P., R. J. Baer, D. P. Casper, D. J. Schingoethe, and S. W. Seas. 1988. Characteristics of milk and butter from cows fed sunflower seeds. 1. Dairy Sci. 71:3179. 18 National Research Council. 1989. Nutrient Requirements of Dairy Cattle. 6th rev. ed. Natl. Acad. Sci. Washington, DC. 19Palmquist. D. L., and T. C. Jenkins. 1980. Fat in lactation rations: review. J. Dairy Sci. 63:l. 20 Palmquist, D. L., M. R. Weisbjerg, and T. Hvelplund. 1993. Ruminal, intestinal, and total digestibilities of nutrients in cows fed diets high in fat and undegradable protein. J. Dairy Sci. 76:1353. 21 Oliveira, J. S., J. T. Huber, D. Ben-Ghedalia, R. S. Swingle, C. B. Theurer, and M. Pessarakli. 1993. Influence of sorghum grain processing on performance of lactating dairy cows. J. Dairy Sci. 76575. 22 Robertson, J. B., and P. J. Van Soest. 1981. The detergent system of analysis and its application to human foods. Page 123 in The Analysis of Dietary Fiber in Food.Vol. 3. W.P.T. James and 0. Theander, ed. Marcel Dekker, New York, NY. 23SAS" User's Guide: Statistics, Version 5 Edition. 1985. SAS Inst., Inc., Cary, NC. 24Schauff. D. J., J. P. Elliott, J. H. Clark, and J. K. Drackley. 1992. Effects of feeding lactating dairy cows diets containing whole soybeans and tallow. J. Dairy Sci. 75:1923. 25 Simas, J., J. T. Huber, Z. Wu, C. B. Theurer, R. S. Swingle. K. H.Chen, and S. C. Chan. 1992. Effect of steam-flaked sorghum grain on milk and milk component yields in cows fed supplemental fat. J. Dairy Sci. 7XSuppl. 1):2%.(Abstr.) 26 Smith, N. E., L. S. Collar, D. L. Bath, W. L. Dunkley, and A. A. Franke. 1981. Digestibility and effects of whole cottonseed fed to lactating cows. J. Dairy Sci. 64:2209. 27Sukhija P. S.. and D. L. Palmquist. 1988. Rapid method for determination of total fatty acid content and composition of feedstuffs and feces. J. Agcic. Food Chem. 36:1202. 28 Teter, B. B., J. Sampugna M. Keeney, and J. Vandersall. 1969. Effects of fish meal feeding on milk and rumen fatty acid composition. J. Dairy Sci. 72(Suppl. 1):549 . ( A b . ) 29 Wu, Z., J. T. Huber, F. T. Sleiman, J. M. Simas, K. H. Chen, S. C. Chan, and C. Fontes. 1993. Effect of three supplemental fat sources on lactation and digestion in dairy cows. J. Dairy Sci. 763562. 30Wu, Z., 0. A. Ohajukuka and D. L. Palmquist. 1991. Ruminal synthesis, biohydrogenation, and digestibility of fatty acids by dairy cows. J. Dairy Sci. 743025.
Journal of Dairy Science Vol. 77, No. 6, 1994
= safflower oil, WCS = whole cottonseed, WCSPT = WCS plus 2.2% prilled tallow fatty acids, WCSPT+ = WCS plus 4.4% prilled tallow fatty acids, WCSSO = WCS plus 2.2% safflower oil.
Thirty Holstein cows averaging 50 DIM were assigned to five dietary treatments for 75 d to determine the effects of source and amount of supplemental fat on milk yield, milk composition, and nutrient digestibilities. Diets were 1) control, 2) diet 1 plus 12% whole cottonseed, 3) diet 2 plus 2.2% safflower oil, 4) diet 2 plus 2.2% prilled tallow fatty acids, and 5) diet 2 plus 4.4% prilled tallow fatty acids. Milk yield was increased an average of 2.1 kg/d by addition of 2.2% prilled tallow fatty acids or safflower oil to the diet (7% fatty acids) containing 12% whole cottonseed. However, when fatty acids were increased to 9.1% with additional prilled tallow fatty acids, milk yield, DMI, and fatty acid digestibility decreased. Whole cottonseed alone and in combination with all fat additions decreased milk protein concentrations. Safflower oil increased CI?:~, C18:l,and C18:2 fatty acids in mlk. Digestibilities of OM, NDF, and ADF were not affected by diet. Supplementation of a saturated or unsaturated fat source to increase fatty acid content to 7.0% of dietary DM increased milk yield, but a further increase in fat to 9.1% with the saturated source appeared excessive for cows yielding 30 to 35 kg/ d of milk. (Key words: fat, lactation; digestion, cows)
INTRODUCTION
Abbreviation key: EE = ether extract, FA = fatty acids, FT = prilled tallow fatty acids, SO
Received November 29, 1993. Accepted February 18, 1994. 'This research was partially supported by Milk Specialties Co.,Dundee, IL. 2Reprints.
1994 J Dairy Sci 77:1644-1651
In a previous study (29), addition of fat from prilled tallow fatty acids (PT; Energy Booster@; Milk Specialties Co., Dundee. IL), Ca salts of palm fatty acids, or tallow to a diet containing 7.2% whole cottonseed (WCS) to increase fat content from 4.2 to 6.7% resulted in average increases of 2.1 kg/d in milk yield. Digestibilities of dietary nutrients, except for fatty acids (FA), were unaffected by addition of fat. In other studies, ruminal fermentation characteristics and nutrient digestibilities were unchanged when 2.2% tallow was added to diets containing 10% whole soybeans (24) or high oil corn (10) for lactating cows, which suggests that tallow or ruminally resistant fats can be combined with oilseeds to maximize dietary fat for lactating cows without depressing digestibilities of other nutrients. Addition of fat to diets for lactating cows increases energy intake in support of higher milk yields, provided it does not reduce DMI. The currently recommended maximum fat concentration is 6 to 7% of dietary DM (18), but this limit was established for cows yielding 20 to 30 kg/d of milk and was based on inhibition of ruminal metabolism and decreased efficiency of milk yield by higher fat. As yield potential of cows has increased and ruminally resistant fats have become available, maximum dietary fat should be reconsidered. Coppock and Wilks (8) suggested that dairy producers include oilseeds in the diet of cows to increase FA from 3% of dietary DM (approximate amount in common lactation diets) to 6%, and to add 3% more FA from ruminally resistant sources for a total of about 9%. However, increased dietary FA from 6.1 to 8.6% of diets
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SUPPLEMENTATION OF FAT FOR DAIRY COWS
for cows yielding approximately 40 kg/d of milk did not enhance milk yield, but reduced DMI (10). Dietary FA at 9% may result in reduced FA digestibility (14) because of limited biliary and pancreatic secretions into the small intestine, although these were not detennined in the study of Elliott et al. (10). The objective of this study was to determine the effects on milk yield and composition and on digestion of nutrients of increasing dietary fat from 3 to 7% by using a combination of WCS and a ruminally resistant fat (a) or safflower oil PO), which is highly unsaturated and not resistant to ruminal hydrolysis. Response of cows to a further increase in dietary fat from 7 to 9% with PT also was tested.
TABLE 1. Ingredient and nutrient composition of diets varying in fat content for lactating cows. Diet Item Ingredient, 5% of DM Alfalfa hay Whok cottonseed Cottonseed hulls
corn Wheat mill run
Barley cononseed meal Minerals and vitamins2 Molasses
Urea Composition of DM NEL,~Mcavkg CP, %
ADF, % NDF, %
MATERIALS AND METHODS
Holstein cows (n = 30; 25 multiparous) averaging 50 DIM were fed the normal herd diet (containing 38% alfalfa hay, 12% WCS, 4% cottonseed hulls, and 46% concentrate mix) during a 14-d pretreatment period. Based on pretreatment milk yield, DIM, and parity, cows were assigned to six outcome groups and allotted randomly to five dietary treatments for 75 d. Estimated content of ether extract @E) (18) of the basal diet (control) was 3.1% (Table 1). Other dietary treatments were basal diet plus 12% WCS (5.2% EE), WCS plus 2.2% SO (wcsso; 7.4% EE), wcs plus 2.2% PT (wCSPT; 7.4% EE), or WCS plus 4.4% PT (WCSPT+; 9.6% EE). Diets containing 7.4% EE were in accordance with recommendations (18) for added fat, but 9.6% EE was projected as a high amount; similar additions of SO and PT permitted comparison of the two supplements. The SO and PT were added to the WCS diet, so all other ingredients were diluted by added fat. To prepare the WCSSO diet, SO first was mixed with the concentrate portion of T M R to enhance handling. Cows were housed in group pens of 10 each, offered diets once daily, and milked at 0800, 1600, and 2400 h. Amounts of TMR offered to individual cows were adjusted daily for 10% orts as measured with Calm gates (American Calan Inc., Northwood, NH). Cows were weighed after the 1600-h milking for 2 consecutive d at the beginning and end of
Control
WCS'
43.0
38.0 12.0 4.0 22.0 9.9 6.9 2.7 2.1 1.8
...
6.5 24.0 10.9 7.7 3.0 2.3 2.0 .6 1.51 18.6 20.8 31.1
.5
1.64 18.9 21.6 32.5
'A diet containing whole cottonseed. Additionally,
three more diets were formed by addition of prilled tallow fatty acids at 2.2 or 4.4%or d o w e r oil at 2.2% to the
wcs
diet. 2A commercial supplement containing 33.3% calcium carbonate., 38.7% dicalcium phosphate. 17.3% tracemineralized salts, and 10.7%vitamins A, Dj. and E ( ~ c u latcd to furnish 50,000 IU of vitamin A, 5,000 IU of vitamin D3. and 250 mg of vitamin Wd per cow). 3Estimated from NRC (18).
treatment. Daily BW change during treatment was calculated for statistical analysis. From d 48 to 62 of treatment, T M R were mixed with .l% Cr2O3 as a digesta marker to measure nutrient digestibilities. The Cr2O3 (1.5 kg) was first mixed with concentrate (22.5 kg) using a cement mixer, and the mixture then was blended into the TMR (1476 kg) to obtain the correct concentration of Cr. From d 58 to 62 of treatment, T M R and orts were sampled once daily, and feces were sampled twice daily immediately after the milkings at 0800 and 1600 h. Samples were composited for the 5-d collection, and nutrient digestibilities were determined from ratios of Cr concentrations in diets consumed to concentrations in feces. For the remainder of the experiment (other than d 58 to 62), weekly samples of TMR and orts were composited by treatment for nutrient analysis. Samples of T M R and orts were air dried, and fecal samples were dried in an oven at J o d of Dairy Science Vol. 77, No. 6, 1994
1646
WU ET AL.
TABLE 2. Fatty acid composition of whole cottonseed, prilled tallow fatty acids, and safflower oil.
was according to the method of Fenton and Fenton (11). Milk samples were collected weekly from Prilled tallow Safflower Fatty Whole acid cottonseed fatty acids1 oil2 three consecutive milkings from the initial week of pretreatment to the end of treatment, (dl00 g of methyl esters) and daily composites were analyzed at the DHI c14:0 1 .o 3.7 .I laboratory (Phoenix, AZ) for fat, protein, lac41.9 8.4 c16:0 26.3 40.0 2.6 3.1 c18:0 tose, and total solids according to infrared 3.1 16.3 c18:l 18.3 procedures; SCC were determined using a .5 69.9 c18:2 46.9 white blood cell counting method (Foss 360; 4.4 Other FA 10.8 2.7 Foss Technology, Eden Prairie, MN); SNF was 1Obtained from Milk Specialties Co. (Dundee, E,). calculated by difference between total solids Trade name, Energy Booster@. and fat. Milk samples from wk 8 of treatment 2Obtained from Chicasha Cotton Oil Co. (Casa Grande, also were analyzed for FA as methyl esters a). (27) using the GLC. Data were subjected to ANOVA by the general linear models procedure of SAS (23) for randomized block designs. The data from 50°C for 48 h. All samples were ground in a the 14-d pretreatment period were used for cyclone mill (Udy Co., Fort Collins, CO) to covariate adjustment of DMI, milk yield, and pass a 1-mm screen and analyzed for DM milk composition. Preplanned contrasts were (100°C for 24 h), OM by the method of AOAC control versus WCS, WCSSO versus WCSPT, (2), CP by AOAC (2) using a digestion system control plus WCS versus WCSSO plus (TecatorB; Hoganas, Sweden) and N auto- WCSPT, and WCSPT versus WCSPT+. Siganalyzer (Bran and Luebbe, Analyzing Tech- nificance was declared at P < .10 unless othernologies, Elmsford, NY), and ADF and NDF wise indicated. according to the methods of Robertson and Van Soest (22). Long-chain FA in fat sources RESULTS AND DISCUSSION and TMR were analyzed according to the method described by Abu-Salah et al. (1). Total Table 2 shows the quantity of the major FA FA in feces were determined by the method of in fat supplements used in the study. The SO Sukhija and Palmquist (27) using GLC (model contained a large amount of c18:2 (70%); PT 3300; Varian Associates, Inc., Walnut Creek, was high in c16:O and c18:O; and WCS fat was CA). Analysis of Cr in TMR, orts, and feces intermediate in c16:O and c l 8 : 1 , but relatively
-
-
TABLE 3. Fatty acid (methyl esters) content and composition of diets (DM basis) for lactating cows. Diet1 Fattv acid Content, % of DM c140 c16:0 c18:0 c18:l c18:2
c18:3
c20:4 Other
wcs
C 3.2
4.9
.I
.8 23.3 3.2 16.8 42.2 5.0 1.7 7.0
20.8 4.5 16.2 38.0 8.3 2.7 8.8
wcsso
WCSPT
7.0 6.9 (g/lOO g of methyl esters) .7 1.5 19.1 26.9 4.0 18.8 16.3 10.9 48.0 25.3 3.4 4.1 1.1 1.3 7.4 11.2
wcsPT+ 9.1 2.0 32.2 26.1 12.0 16.9 2.4 1.1 7.3
'Dietary treatments: C = control, WCS = 12% whole cottonseed, WCSSO = WCS plus 2.2%safflower oil, WCSPT = WCS plus 2.2% prilled tallow fatty acids, and WCSPT+ = WCS plus 4.4% prilled tallow fatly acids. Journal of Dairy Science Vol. 77, No. 6, 1994
SUPPLEMENTATION OF FAT FOR DAIRY COWS
high in c18:2. Linoleic acid (c18:2) was more inhibitory to ruminal microbes than were c16:O and C18:O (6). Long-chain FA in all diets (Table 3) were lower than projected from the EE content of feeds (18), but EE includes lipids and glycerol that are not FA. However, FA differences among diets were as planned. The FA content in diets showed high c18:2 in WCSSO, and high c16:O and c18:O in WCSPT and WCSPT+, reflecting the FA composition of the fat supplements. Milk yield of cows did not differ between the control and WCS diets (Table 4). Whole cottonseed, an economical feedstuff in some regions, is high in fiber and energy and can be used as a substitute for forages and concentrates, as well as a supplemental fat source. In support of these findings, WCS failed to increase milk yields from those of other studies (9, 16, 26). Compared with the control and WCS diets, WCSSO and WCSPT increased (P < .05) milk yield an average of 2.1 kg/d; no difference was found between WCSSO and WCSPT. In a previous study (29), addition of 2.2% tallow, PT, or Ca salts of palm FA increased milk yield similarly. In the present study, alleged ruminal resistance of PT did not increase milk yield compared with that of SO when both were added at 2.2% of the diet. Milk yields were not significantly different for WCSPT (34.3 kdd) and WCSpT+ (33.0 kg/ d), but DMI was lower for WCSPT+, 26.8 and 24.1 kg/d for the respective diets. Other diets (control, WCS, and WCSSO) were somewhat higher in DMI than WCSPT+ and did not T differ from WCSPT. Similarly, addition of E to diets at 2.5% of DM did not adversely affect DMI in other studies (7, 29). The decrease in DMI with 4.4% PT was probably because of excessive fat supplementation (9.1% total FA) and not because of the fat source. Lack of increased milk yield with similarly high intakes of dietary fat also was shown by Ferguson et al. (12) for cows yielding 19 kg/d of milk, and by Elliott et al. (10) and Holter et al. (13) for cows yielding up to 40 kg/d of milk. Diets did not affect BW gain of cows, even though cows fed WCSPT+ tended to gain less than other groups. Percentage of milk protein was lower (P c .04)for cows fed WCS than for controls (Table
1647
4), but did not differ significantly in other
contrasts. However, milk protein generally was decreased for all diets with supplemental fat. Yield of milk protein was not altered by amount of dietary fat, as demonstrated in other studies (25, 29). Restriction in AA availability for milk protein synthesis appears to be a likely hypothesis (4) for explaining the decrease in milk protein percentage with added fat. Plasma AA concentrations and mammary blood flows per unit of milk volume were lower (3), but efficiency of utilization of AA in the mammary gland was higher (3,5),for cows receiving supplemental fat than for control cows; this result suggested that decreases in milk protein concentration with added fat may result from an insufficient supply of AA to the mammary gland to sustain a greater milk protein synthesis needed to accompany the increased milk yields stimulated by fat supplementation. Percentages of fat, lactose, and SNF of milk and SCC in milk were not affected by treatment, but yields of milk and 3.5% FCM were higher for WCSSO and WSCPT than for control and WCS. Fat percentage for WCSSO was somewhat lower than for WCSPT. Fat sources high in c18:2 decrease milk fat concentrations (15, 17) because of an inhibition of ruminal cellulolytic bacteria by c18:2 and inhibition of FA synthesis in the mammary gland (19). The inhibition of mammary FA synthesis may be via rrans-C18,1 (28), which originates mainly from ruminal biohydrogenation of c18:2, when this FA is fed in large amounts (30). However, concentrations of t?-ans-Clg:lin milk fat were not measured. Composition of milk FA is shown in Table 5. Because FA were converted to methyl esters for analysis, and not to butyl esters, the shortchain FA, especially C ~ Omight , have been underestimated, which would lead to overestimates of the percentages of long-chain FA. Percentages of c18:O. c18:17 and c18:2 FA in milk fat increased, but C40 to C14:o decreased, when WCS, PT, or SO was fed. Milk from cows fed the SO diet only had 18% of its FA as C4:o to C14:0, compared with 33% for the controls, suggesting that SO may have compromised de novo fatty acid synthesis in the mammary gland through a decrease in ruminal acetate production (6). Addition of 4.4% compared with 2.2% PT resulted in slight increases Journal of Dairy Science Vol. 77, No. 6, 1994
k
8
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SUPPLEMENTATION OF FAT FOR DAIRY COWS
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J o d of Dairy Science Vol. 77, No. 6, 1994
1650
WU ET A L
TABLE 6. Apparent total tract digestibilities of components in diets supplemented with different sources and amounts of fat for lactating cows. Contrast
c vs. Item
C
WCS WCSSO WCSPT WCSPT+ SEM WCS
OM
53 58 45 45
56 59 45 47
76
74
CP ADF NDF Fatty acid
P <
46
(96) 58 64 46 45
57 69 47 48
2 2 5 4
74
76
69
4
56 60 45
WCSSO vs. c + wcs vs. WCSPT vs. WCSPT WCSSO + WCSPTWCSPT+
.13 NS NS
NS NS NS NS
.12 NS NS NS
NSZ .02 NS NS
NS
NS
NS
NS
NS
'Dietary treatments: C = control, WCS = 12% whole cottonseed, WCSSO = WCS plus 2.2% safflower oil, WCSFT = WCS plus 2.2% prilled tallow fatty acids, and WCSPT+ = WCS plus 4.4% prilled tallow fatty acids. ZP > .15.
in c16:O and c18:~, but decreases in C14:o and C18:2, which could not be attributed entirely to the FA of FT. At the same percentage of supplementation and compared with PT, SO increased the percentages of CIS:^, c18:2, and C18:3, and decreased percentages of C p o , C149, and c16:0, which are mostly synthesized in the mammary gland, suggesting some inhibition of FA synthesis by SO. Digestibilities of OM were relatively low for all diets (Table 6), reflecting the high DMI, which averaged 4.6% of BW for all treatments. Digestibilities of DMI and OM were similar to those for diets with alfalfa hay, cottonseed, and cottonseed hulls as fiber sources observed in other studies (21, 29). The OM digestibility for the control diet tended to be lower (P < .13) than that for WCS as well as for other diets, partly because of lower CP digestibility. Supplemental fat enhanced CP digestibility and was associated with increased ruminal N H 3 losses (20). Digestibilities of ADF and NDF were unaffected by amount or source of dietary fat. The lower DMI for WCSP"+ might favor increased digestion of ADF and NDF because of longer retention time in the rumen. Although FA digestibilities were quite variable (Table 6), they averaged 74.8% after the value for WCSPT+ was excluded and approximated those (76.4%) determined previously using similar fat percentages (29). Digestibility of FA for WCSFT+ tended to be lowest, suggesting that increased FA content from 7.0 to 9.1% of the diet decreased FA digestibility. Jointly Journal of Dairy Science Vol. 77, No. 6, 1994
with the decreased DMI, the lowered FA digestibility might have been responsible for the tendency of lower milk yield for WCSPT+ than for WCSPT. CONCLUSIONS
Milk yield of cows was increased by WCSPT or WCSSO diets, which increased dietary FA to 7.0% of DM, but numerically decreased when PT was fed to increase dietary FA from 7.0 to 9.1%. No difference in milk yield of cows was found between the WCSPT and WCSSO diets. The WCSFT+ diet decreased DMI and tended to decrease FA digestibility. Addition of fat did not affect apparent digestibilities of OM, ADF, or NDF. The WCSSO diet increased the percentages of C18:1, C18:2, and C18:3 FA in milk. Ruminal saturation of FA from the WCSSO diet might have precluded significant decreases in milk fat percentage and digestion of nutrients. Fat at 9.1% of dietary DM appeared to be excessive for cows yielding 30 to 40 kg/d of milk. ACKNOWLEDGMENTS
The authors greatly appreciate the expertise in analyzing samples of M. Francolin, K. Y. Lei, and F. Rosenstein. REFERENCES
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