Dietary Fat and Ruminally Protected Amino Acids for High Producing Dairy Cows1 C. J. CANALE, L. D. MULLER, H. A. McCAHON, T. J. WHrTSEL, G. A. VARGA, and M. J. LORMORE Department of Dairy and Animal SCience The Pennsylvania State University University Park Pennsylvania 16802
ABSTRACT
INTRODUCTION
Eight early lactation Holstein cows, used in a replicated 4 x 4 Latin square design, were fed the following diets: control; control plus ruminally protected amino acids (15 g methionine and 20 g lysine); control plus added fat (.32 kg 60: 40 animal and vegetable blend and .36 kg of Ca salts of fatty acids); control plus ruminally protected amino acids plus added fat The objective was to examine the effect of ruminally protected fonns of lysine and methionine and dietary fat on milk yield and composition. Cows were fed for ad libitum consumption of total mixed diets consisting of 50% forage and 50% concentrate on a DM basis. Added fat increased milk, fat, and 4% FCM yield but decreased milk protein percentage. Ruminally protected amino acids increased milk protein percentage. The combined effect of fat and ruminally protected acids increased milk fat percentage and yield more than the sole addition of either supplement. Added fat increased the percentage and yield of long-chain fatty acids in milk. Plasma free fatty acids were also increased by fat addition. Adding ruminally protected amino acids to fat-supplemented diets may help alleviate the milk protein depression found with added fat. (Key words: dietary fat, ruminally pr0tected amino acids, milk yield)
Adding fat (and high fat feedstuffs) to increase the energy density and energy intake of diets for early lactation dairy cows is becoming common (1, 20). Use of dietary fat may continue to increase as the genetic potential for milk production increases. However, feeding large amounts of ruminally unprotected fat may have detrimental effects on fiber digestibility (21). The development of Ca salts of fatty acids (caS), which are considered inert in the rumen, offers a method of increasing the energy density of diets without affecting fiber digestion. Rumen fennentation is not affected with caS because the caS complex is insoluble in the rumen (3. 4), provided that rumen pH is maintained above 6.0 (22). A decreased milk protein percentage has been reported with added fat (I, 2, 21). This decrease averages about .1 to .15% and is of economic importance as more fluid milk is priced on protein content. The mechanism for this decrease, however. has not been elucidated. Nutritionists have long attempted to improve milk protein content and yield. Inadequate amino acids presented to the duodenum for subsequent absorption can limit the yield of milk and milk components, namely, protein (6). Lysine and methionine have been identified as potentially limiting amino acids for milk protein synthesis, particularly when com-based diets are fed (28, 29). Encapsulation of amino acids with polymeric compounds has effectively delivered amino acids postruminally (7. 9, 24, 25, 26). Ruminally protected amino acids (RPAA) have increased milk protein percentage in cows fed diets based on com silage (9, 26) and grass silage (12); supplying 10 to 16 g of ruminally protected methionine (RP-Met) and 18 to 40 g of ruminaUy protected lysine (RP-Lys)/d per cow improved milk protein percentage. Donkin
Received March 27,1989. Accepted July 17. 1989. 1Authorized for publication as Paper Nwnber 8135 in the Journal Series of The Pennsylvania Agricultural Experimenl Station.
1990 J Dairy Sci 73:135-141
135
136
CANALE ET AL.
et al. (9) reported that RPAA (15 g methionine and 40 g lysine/d) increased a-casein and pcasein and decreased lC-casein in cow's mille The decreased milk protein percentage reported with added fat may be related to decreased casein content (8, 11). Supplementation with RPAA may alleviate the decrease in milk protein percentage that occurs with fat supplementation. Our objective was to examine the addition ofRP-Met (15 g/d) and RP-Lys (20 g/d) and dietary fat on milk yield and milk composition of high producing dairy cows. MATERIALS AND METHODS Animals and Treatments
Eight early lactation Holstein cows (ranging from 50 to 80 d postpartum) were used in a replicated 4 x 4 Latin square designed experiment. One square consisted of four primiparous cows, averaging 30 kg milk/d at the beginning of the experiment, and the other square consisted of four multiparous cows, averaging 41 kg milk/d at the beginning of the experiment. Each experimental period consisted of 21 d with the last 10 d of each period used for data collection. Due to a teat injury, data from one primiparous cow were omitted during periods 2, 3, and 4. The four treatments were: diet 1, control (C); diet 2, C plus RPAA; diet 3, C plus added fat (F); diet 4, C plus RPAA plus F. Diet 1 (DM basis) consisted of 50% forage (33% com silage and 17% alfalfa hay crop silage) and 50% concentrate, formulated to meet or exceed NRC requirements (18) for cows weighing 600 kg and producing 35 kg milk/d. Diets were fed as total mixed rations (TMR). Fat was added to provide approximately .32 kg animal-vegetable (60:40) blend (Moyer Packing Co., Souderton, PA) and .36 kg CaS (Church & Dwight Co., Inc., Princeton, NJ) per cow daily. The combination of RPAA was designed to deliver a total of 15 g of RP-Met/d and 20 g of RP-Lys/d. The RP-Met and RP-Lys were mixed with the TMR during each a.m. feeding. The pH-sensitive encapsulation material (7) protects amino acids from ruminal degradation (24). Cows were individually fed twice daily and refusals measured once daily. Dry matter content of feeds was determined weekly by oven Journal of Dairy Science Vol. 73,
No.1, 1990
drying at IOO·C and diets adjusted as necessary to maintain a 50:50 forage:grain ratio. Samples of feeds were collected weekly and frozen for later analyses. Feed samples were sampled twice weekly and composited by experimental period. All chemical analyses were performed at the New York Forage Testing Laboratory, Ithaca. NY. Measurements and sample Analyses
Milk yield was recorded daily during the last 10 d of each experimental period. Cows were
milked daily at 0530 and 1600 h. During each period, milk samples were collected at two consecutive milkings on 4 d between d II and 21, preserved with potassium dichromate, and stored at 4°C. Milk samples taken from each a.m. and p.m. milking were composited daily, proportioned according to volume, and analyzed for protein and fat at the Pennsylvania DHI Central Milk Testing Laboratory. Protein and fat were determined using a Foss 203B Milko-Scan (Foss Electric, Hillerod, Denmark). A composite samples was frozen for fatty acid analyses. Milk fat was extracted by the procedures of Mojonnier (17) and the lipid fraction stored (-20·C) under N2 in an excess of petroleum ether. Methylation of fatty acids was performed prior to gas liquid chromatography (5). One microliter of each sample was injected by hand into a 5890 Hewlett Packard gas chromatograph (Avondale, PA) equipped with a 2 m. GP 10% SP 2330 column with 100/120 chromosorb WAW packing. Oven temperature began at 4O·C and increased 8°C/min until a maximum temperature of 180°C was reached. Temperature of injector and detector was 2IO·C. Nitrogen and hydrogen flow rate was 20 mIl min and total run time equaled 40 min. Blood samples were collected by jugular venipuncture into heparanized vacutainer tubes during the last day of each period at 3 h postfeeding. Sample tubes were centrifuged at 3000 x g for 10 min and the plasma was removed for analyses of non-esterified fatty acids (Wako Chemicals USA, Inc., Dallas, TX). Statistical Analysis
Data were analyzed as a replicated 4 x 4 Latin square using the General Linear Models
DIETARY FAT AND RUMINALLY PROTECIED AMINO ACIDS
procedure of SAS (27). Square, cow within square, period, treaunent. and the interaction of square with treatment were sources of variation. The model employed for statistical analysis was following:
where:
= overall mean, = square effect, effect of cow nested in square, C~~ = = period effect, TI = treatment effect, (ST)i\ = square x treatment interaction, and Eijldm = experimental error. 1.1 Si
Means were compared by linear contrasts, designed to test the following: fat vs. no fat. RPAA vs. no RPAA, and the interaction of fat and RPAA. Effects were considered different based on significant (P
ABSTRACT
INTRODUCTION
Eight early lactation Holstein cows, used in a replicated 4 x 4 Latin square design, were fed the following diets: control; control plus ruminally protected amino acids (15 g methionine and 20 g lysine); control plus added fat (.32 kg 60: 40 animal and vegetable blend and .36 kg of Ca salts of fatty acids); control plus ruminally protected amino acids plus added fat The objective was to examine the effect of ruminally protected fonns of lysine and methionine and dietary fat on milk yield and composition. Cows were fed for ad libitum consumption of total mixed diets consisting of 50% forage and 50% concentrate on a DM basis. Added fat increased milk, fat, and 4% FCM yield but decreased milk protein percentage. Ruminally protected amino acids increased milk protein percentage. The combined effect of fat and ruminally protected acids increased milk fat percentage and yield more than the sole addition of either supplement. Added fat increased the percentage and yield of long-chain fatty acids in milk. Plasma free fatty acids were also increased by fat addition. Adding ruminally protected amino acids to fat-supplemented diets may help alleviate the milk protein depression found with added fat. (Key words: dietary fat, ruminally pr0tected amino acids, milk yield)
Adding fat (and high fat feedstuffs) to increase the energy density and energy intake of diets for early lactation dairy cows is becoming common (1, 20). Use of dietary fat may continue to increase as the genetic potential for milk production increases. However, feeding large amounts of ruminally unprotected fat may have detrimental effects on fiber digestibility (21). The development of Ca salts of fatty acids (caS), which are considered inert in the rumen, offers a method of increasing the energy density of diets without affecting fiber digestion. Rumen fennentation is not affected with caS because the caS complex is insoluble in the rumen (3. 4), provided that rumen pH is maintained above 6.0 (22). A decreased milk protein percentage has been reported with added fat (I, 2, 21). This decrease averages about .1 to .15% and is of economic importance as more fluid milk is priced on protein content. The mechanism for this decrease, however. has not been elucidated. Nutritionists have long attempted to improve milk protein content and yield. Inadequate amino acids presented to the duodenum for subsequent absorption can limit the yield of milk and milk components, namely, protein (6). Lysine and methionine have been identified as potentially limiting amino acids for milk protein synthesis, particularly when com-based diets are fed (28, 29). Encapsulation of amino acids with polymeric compounds has effectively delivered amino acids postruminally (7. 9, 24, 25, 26). Ruminally protected amino acids (RPAA) have increased milk protein percentage in cows fed diets based on com silage (9, 26) and grass silage (12); supplying 10 to 16 g of ruminally protected methionine (RP-Met) and 18 to 40 g of ruminaUy protected lysine (RP-Lys)/d per cow improved milk protein percentage. Donkin
Received March 27,1989. Accepted July 17. 1989. 1Authorized for publication as Paper Nwnber 8135 in the Journal Series of The Pennsylvania Agricultural Experimenl Station.
1990 J Dairy Sci 73:135-141
135
136
CANALE ET AL.
et al. (9) reported that RPAA (15 g methionine and 40 g lysine/d) increased a-casein and pcasein and decreased lC-casein in cow's mille The decreased milk protein percentage reported with added fat may be related to decreased casein content (8, 11). Supplementation with RPAA may alleviate the decrease in milk protein percentage that occurs with fat supplementation. Our objective was to examine the addition ofRP-Met (15 g/d) and RP-Lys (20 g/d) and dietary fat on milk yield and milk composition of high producing dairy cows. MATERIALS AND METHODS Animals and Treatments
Eight early lactation Holstein cows (ranging from 50 to 80 d postpartum) were used in a replicated 4 x 4 Latin square designed experiment. One square consisted of four primiparous cows, averaging 30 kg milk/d at the beginning of the experiment, and the other square consisted of four multiparous cows, averaging 41 kg milk/d at the beginning of the experiment. Each experimental period consisted of 21 d with the last 10 d of each period used for data collection. Due to a teat injury, data from one primiparous cow were omitted during periods 2, 3, and 4. The four treatments were: diet 1, control (C); diet 2, C plus RPAA; diet 3, C plus added fat (F); diet 4, C plus RPAA plus F. Diet 1 (DM basis) consisted of 50% forage (33% com silage and 17% alfalfa hay crop silage) and 50% concentrate, formulated to meet or exceed NRC requirements (18) for cows weighing 600 kg and producing 35 kg milk/d. Diets were fed as total mixed rations (TMR). Fat was added to provide approximately .32 kg animal-vegetable (60:40) blend (Moyer Packing Co., Souderton, PA) and .36 kg CaS (Church & Dwight Co., Inc., Princeton, NJ) per cow daily. The combination of RPAA was designed to deliver a total of 15 g of RP-Met/d and 20 g of RP-Lys/d. The RP-Met and RP-Lys were mixed with the TMR during each a.m. feeding. The pH-sensitive encapsulation material (7) protects amino acids from ruminal degradation (24). Cows were individually fed twice daily and refusals measured once daily. Dry matter content of feeds was determined weekly by oven Journal of Dairy Science Vol. 73,
No.1, 1990
drying at IOO·C and diets adjusted as necessary to maintain a 50:50 forage:grain ratio. Samples of feeds were collected weekly and frozen for later analyses. Feed samples were sampled twice weekly and composited by experimental period. All chemical analyses were performed at the New York Forage Testing Laboratory, Ithaca. NY. Measurements and sample Analyses
Milk yield was recorded daily during the last 10 d of each experimental period. Cows were
milked daily at 0530 and 1600 h. During each period, milk samples were collected at two consecutive milkings on 4 d between d II and 21, preserved with potassium dichromate, and stored at 4°C. Milk samples taken from each a.m. and p.m. milking were composited daily, proportioned according to volume, and analyzed for protein and fat at the Pennsylvania DHI Central Milk Testing Laboratory. Protein and fat were determined using a Foss 203B Milko-Scan (Foss Electric, Hillerod, Denmark). A composite samples was frozen for fatty acid analyses. Milk fat was extracted by the procedures of Mojonnier (17) and the lipid fraction stored (-20·C) under N2 in an excess of petroleum ether. Methylation of fatty acids was performed prior to gas liquid chromatography (5). One microliter of each sample was injected by hand into a 5890 Hewlett Packard gas chromatograph (Avondale, PA) equipped with a 2 m. GP 10% SP 2330 column with 100/120 chromosorb WAW packing. Oven temperature began at 4O·C and increased 8°C/min until a maximum temperature of 180°C was reached. Temperature of injector and detector was 2IO·C. Nitrogen and hydrogen flow rate was 20 mIl min and total run time equaled 40 min. Blood samples were collected by jugular venipuncture into heparanized vacutainer tubes during the last day of each period at 3 h postfeeding. Sample tubes were centrifuged at 3000 x g for 10 min and the plasma was removed for analyses of non-esterified fatty acids (Wako Chemicals USA, Inc., Dallas, TX). Statistical Analysis
Data were analyzed as a replicated 4 x 4 Latin square using the General Linear Models
DIETARY FAT AND RUMINALLY PROTECIED AMINO ACIDS
procedure of SAS (27). Square, cow within square, period, treaunent. and the interaction of square with treatment were sources of variation. The model employed for statistical analysis was following:
where:
= overall mean, = square effect, effect of cow nested in square, C~~ = = period effect, TI = treatment effect, (ST)i\ = square x treatment interaction, and Eijldm = experimental error. 1.1 Si
Means were compared by linear contrasts, designed to test the following: fat vs. no fat. RPAA vs. no RPAA, and the interaction of fat and RPAA. Effects were considered different based on significant (P
