Effects of Dietary Protein Degradability and Casein or Amino Acid Infusions on Production and Plasma Amino Acids in Dairy Cows WILLIAM M. SEYMOUR,1 CARL E. POLAN, and JOSEPH H. HERBEIN Department of Dairy SCience Virginia Agricultural Experiment Station College of Agriculture and Life Sciences Virginia Polytechnic Institute and State University Blacksburg 24061 ABSTRACT
Responses to daily abomasal infusions of 400 g sodium caseinate, 400 g hydrolyzed casein, or 11.3 g L-methionine plus 30.1 g L-lysine were compared in eight Holstein cows fed diets with estimated ruminal protein degradabilities of 70 and 60.5%. Basal diets contained corn silage and corn with either soybean meal or 66.7:33.3 soybean meal:corn gluten meal added. Infusion with Methionine plus lysine increased milk protein content when cows were fed either diet but increased milk fat content and yield only when the soybean meal diet was fed. Sodium caseinate increased milk and milk protein production and decreased milk fat percentage. Concentration of total essential amino acids, branched chain amino acids, and urea cycle amino acids were increased by the infusion of both casein sources. Methionine-lysine infusion increased plasma lysine and taurine, a metabolite of methionine, suggesting that absorbed methionine was extensively metabolized. Results demonstrate an impact of both ruminal degradability of dietary protein and form of infused protein on amino acid nutrition of lactating dairy cows. (Key words: casein, amino acids, abomasal infusion) INTRODUCTION
Although protein nutrition of dairy cattle has been studied extensively in terms of response to
Received December 7. 1988. Accepted August 28.1989. IPresenl address: Research and Development Department. Agway Inc.• Syracuse. NY 13221. 1990 J Dairy Sci 73:735-748
dietary crude protein (10), individual amino acid requirements for lactation have not been determined. Significant increases in the efficiency of protein utilization could be realized if the limiting amino acids for milk production were identified and fed in a form that would escape degradation in the rumen (10, 20). Despite the high rate of proteolysis in the rumen, undegraded feed protein accounts for 50 to 55% of the total protein available for postruminal digestion (14, 20). Therefore, given a relatively constant amino acid profile of microbial protein (24), amino acid profile of digesta flowing to the small intestine might be altered by both the amount and source of undegraded protein in the diet (14,20). However, few direct effects of dietary protein degradability on amino acid metabolism and milk yield of cows have been shown. Abomasal infusion of sodium caseinate (4) or protein concentrates (18) increases milk and milk protein yield 10 to 15% in cows producing over 30 kg of milk/d and fed according to crude protein requirements. Methionine and lysine apparently accounted for the majority of the milk protein response to casein infusion (23) and, in some cases increased milk yield or milk protein production, or bom when infused postruminally or fed in protected forms to cows in early to midlactation (11, 19, 22). A question not addressed in these studies was the effect of degradability of dietary protein on the response to infused casein or amino acids. This is relevant in view of the National Research Council's adoption of the rumen degradable protein concept (14) and the long-term goal of regulating postruminal amino acid supply in ruminants by feeding rumen-protected protein or amino acids (20). Finally, there are questions concerning me effect of chemical form of protein (intact versus free amino acids) on the efficiency of its diges-
735
736
SEYMOUR ET AL.
tion and absorption (26). Evidence suggests that intact protein fed to rats is utilized more· efficiently than a corresponding mi~tur~ ?f ~ee amino acids (9). Such differences m utlhzatlon would be important in detennining whether intact proteins or individual amino acids should be protected from rumen degradation. Th~ objective of this study was to compare lactatlonal perfonnance and plasma free amino acid .concentrations of dairy cows given abomasal mfusions of sodium caseinate, casein hydrolysate, methionine (Met) plus lysine (Lys), or water when fed two diets differing in rumen protein degradability. MATERIALS AND METHODS
Animals Eight multiparous Holstein cows began. the experiment between 117 and 149 d of lacta~on. Average age, body weight, and mature equivalent milk production were 50 mo, 570 kg, and 7531 kg. Cows were housed in comfort stalls, fed 35% of their daily ration at 0600 h and 65% at 1400 h, and milked at 1200 and 2400 h in .a milking parlor. All cows had undergone surgical procedures for installation of a rumen cannula at least 60 d before starting the expriment. Similarly, four cows had been equipped with duodenal cannula. Total mixed diets contained com silage and high moisture com, supplemented with either soybean meal (soy) or a mixture of soybean meal and com gluten meal (soy-gluten); DM ratio of 66.7% soy to 33.3% com gluten meal; plus a vitamin-mineral premix (Table 1). The diets were fed for ad libitum intake (10% refusals). Both diets were balanced according to 1978 NRC requirements (15) for net energy, ADF, CP, and trace nutrients. The soy-gluten diet was fonnulated to contain 60.5% rumen degradable CP and provided 115% of NRC recommendations for undegraded intake protein, based on observed intakes. The soy diet was fonnulated at 70% rumen degradable protein and provided 90% of recommende~ undegraded intake protein during the expenment.
2US Biochemicals Corp. Enzymatically hydrolyzed casein: 35% free amino acids, 65% dipeptides and tripeptides. Percentages of sodium, total nitrogen, and ash were similar for the two casein sources. Journal of Dairy Science Vol. 73,
No.3, 1990
Infusions
Abomasal infusion was by the method of Clark et al. (4). Infusions included 400 g sodium caseinate (US Biochemicals Corp., Cleveland, OH),2 400 g enzymatically hydrolyzed casein, or 11.3 g L-Met plus 30.1 g L-Lys in 5 L water, or water alone. Infusions were administered 22 hid via a peristaltic pump (Buchler Multistaltic, Haake-Buchler, Inc., Saddle Brook, NJ). Infusion pumps were disconnected for 1 h twice daily when cows were moved to and from the milking parlor. Solutions were mixed daily, chilled to 4'C, and kept cool during infusion by surrounding reservoirs with ice. The amount of Met and Lys infused was equal to that found in 400 g of sodium caseinate. Design and Application of Treatments
An 8 x 6 incomplete block design was used in order to complete the study before cows entered late lactation. Each cow was assigned a unique sequence of six of the eight treatlnents (diet x infusion combinations), for a total of 48 cow x period observations (Table 2). Each treatlnent was represented in each II-d infusion period. Treatments were arranged such that half of the cows were fed one of the two diets
TABLE 1. Composition of soybean meal (soy) and soybean meal plus com gluten meal (soy-gluten) experimental diets. Item
Soy
(% diet DM) -
Ingredient Com silage, % High moisture com. % Soybean meal, % Com gluten meal. % Vitamin and mineral premix, I % Analysis Dry matter, % Crude protein, % ADF, % Organic maner, %
Soy-gluten
74.3 8.4 14.5 0
74.3 9.6 8.6 4.3
2.8 100.00
3.2 100.00
X 45.2 14.2 21.1 91.0
SD 3.1 2 1.2 1.4 2.2
X 45.0 13.8 20.9 90.3
SD 3.1 1.5 1.5 2.4
lAs fed: Ca 15.9%, P. .7%, K 6.2%. Mg 2.2%, NaHC03 19.4, CI 10.6 ppm, Fe 265 ppm, Cu 132 ppm, co 3 ppm, Mn 1100 ppm, Zn 1323 ppm, I 44 ppm, S~ 5 ppm, vitamin A SO,OOO lU/lb, vitamin D 25,000 IU/lb, vltamm E 500 lU/lb.
AMINO ACID NUTRITION IN DAIRY COWS TABLE 2. Application of treaunents. 1 Period 2
2
3
4
5
6
3
4
2
7
5 8 6
7
4 3
6 5
7
eow3 A B
1
2
c4 04
2
1
4
3
1
8
~
5 8
6 5 8
7
4
I
6 5 8
2
4 3 2
F' G H
7 6
7
1 3
6 8 5 2 3 4 1
ITreatments 1 through 4 were waler (W), sodiwn caseinate (C), hydrolyzed casein, (HC), and methionine-lysine (ML) infusions when cows were fed the soy diet. Treatments 5 through 8 were W, C,HC. and ML infusions when cows were fed the soy-gluten diet. 2Periods were 11 d with periods 3 and 4 separated by a lQ-d interim for diet changes and adaptation. 3Cow H completed periods 1 to 3 only. 4eows samples for plasma amino acid analysis and rumen VFA.
during the first three infusion periods then fed the other diet during a lO-d interim and the remaining three infusion periods (Table 2). Blood and rumen samples were taken from four of the eight cows at the end of each period (description of sampling below). These four cows were equipped with duodenal cannula and were used for determination of digesta flow (to be reported separately). Treatments were arranged such that the four cows constituted an independent experimental group (Table 2) with three observations per diet x infusion treatment. One cow completed only three of the six periods due to low milk yield ( W (P W (P
Responses to daily abomasal infusions of 400 g sodium caseinate, 400 g hydrolyzed casein, or 11.3 g L-methionine plus 30.1 g L-lysine were compared in eight Holstein cows fed diets with estimated ruminal protein degradabilities of 70 and 60.5%. Basal diets contained corn silage and corn with either soybean meal or 66.7:33.3 soybean meal:corn gluten meal added. Infusion with Methionine plus lysine increased milk protein content when cows were fed either diet but increased milk fat content and yield only when the soybean meal diet was fed. Sodium caseinate increased milk and milk protein production and decreased milk fat percentage. Concentration of total essential amino acids, branched chain amino acids, and urea cycle amino acids were increased by the infusion of both casein sources. Methionine-lysine infusion increased plasma lysine and taurine, a metabolite of methionine, suggesting that absorbed methionine was extensively metabolized. Results demonstrate an impact of both ruminal degradability of dietary protein and form of infused protein on amino acid nutrition of lactating dairy cows. (Key words: casein, amino acids, abomasal infusion) INTRODUCTION
Although protein nutrition of dairy cattle has been studied extensively in terms of response to
Received December 7. 1988. Accepted August 28.1989. IPresenl address: Research and Development Department. Agway Inc.• Syracuse. NY 13221. 1990 J Dairy Sci 73:735-748
dietary crude protein (10), individual amino acid requirements for lactation have not been determined. Significant increases in the efficiency of protein utilization could be realized if the limiting amino acids for milk production were identified and fed in a form that would escape degradation in the rumen (10, 20). Despite the high rate of proteolysis in the rumen, undegraded feed protein accounts for 50 to 55% of the total protein available for postruminal digestion (14, 20). Therefore, given a relatively constant amino acid profile of microbial protein (24), amino acid profile of digesta flowing to the small intestine might be altered by both the amount and source of undegraded protein in the diet (14,20). However, few direct effects of dietary protein degradability on amino acid metabolism and milk yield of cows have been shown. Abomasal infusion of sodium caseinate (4) or protein concentrates (18) increases milk and milk protein yield 10 to 15% in cows producing over 30 kg of milk/d and fed according to crude protein requirements. Methionine and lysine apparently accounted for the majority of the milk protein response to casein infusion (23) and, in some cases increased milk yield or milk protein production, or bom when infused postruminally or fed in protected forms to cows in early to midlactation (11, 19, 22). A question not addressed in these studies was the effect of degradability of dietary protein on the response to infused casein or amino acids. This is relevant in view of the National Research Council's adoption of the rumen degradable protein concept (14) and the long-term goal of regulating postruminal amino acid supply in ruminants by feeding rumen-protected protein or amino acids (20). Finally, there are questions concerning me effect of chemical form of protein (intact versus free amino acids) on the efficiency of its diges-
735
736
SEYMOUR ET AL.
tion and absorption (26). Evidence suggests that intact protein fed to rats is utilized more· efficiently than a corresponding mi~tur~ ?f ~ee amino acids (9). Such differences m utlhzatlon would be important in detennining whether intact proteins or individual amino acids should be protected from rumen degradation. Th~ objective of this study was to compare lactatlonal perfonnance and plasma free amino acid .concentrations of dairy cows given abomasal mfusions of sodium caseinate, casein hydrolysate, methionine (Met) plus lysine (Lys), or water when fed two diets differing in rumen protein degradability. MATERIALS AND METHODS
Animals Eight multiparous Holstein cows began. the experiment between 117 and 149 d of lacta~on. Average age, body weight, and mature equivalent milk production were 50 mo, 570 kg, and 7531 kg. Cows were housed in comfort stalls, fed 35% of their daily ration at 0600 h and 65% at 1400 h, and milked at 1200 and 2400 h in .a milking parlor. All cows had undergone surgical procedures for installation of a rumen cannula at least 60 d before starting the expriment. Similarly, four cows had been equipped with duodenal cannula. Total mixed diets contained com silage and high moisture com, supplemented with either soybean meal (soy) or a mixture of soybean meal and com gluten meal (soy-gluten); DM ratio of 66.7% soy to 33.3% com gluten meal; plus a vitamin-mineral premix (Table 1). The diets were fed for ad libitum intake (10% refusals). Both diets were balanced according to 1978 NRC requirements (15) for net energy, ADF, CP, and trace nutrients. The soy-gluten diet was fonnulated to contain 60.5% rumen degradable CP and provided 115% of NRC recommendations for undegraded intake protein, based on observed intakes. The soy diet was fonnulated at 70% rumen degradable protein and provided 90% of recommende~ undegraded intake protein during the expenment.
2US Biochemicals Corp. Enzymatically hydrolyzed casein: 35% free amino acids, 65% dipeptides and tripeptides. Percentages of sodium, total nitrogen, and ash were similar for the two casein sources. Journal of Dairy Science Vol. 73,
No.3, 1990
Infusions
Abomasal infusion was by the method of Clark et al. (4). Infusions included 400 g sodium caseinate (US Biochemicals Corp., Cleveland, OH),2 400 g enzymatically hydrolyzed casein, or 11.3 g L-Met plus 30.1 g L-Lys in 5 L water, or water alone. Infusions were administered 22 hid via a peristaltic pump (Buchler Multistaltic, Haake-Buchler, Inc., Saddle Brook, NJ). Infusion pumps were disconnected for 1 h twice daily when cows were moved to and from the milking parlor. Solutions were mixed daily, chilled to 4'C, and kept cool during infusion by surrounding reservoirs with ice. The amount of Met and Lys infused was equal to that found in 400 g of sodium caseinate. Design and Application of Treatments
An 8 x 6 incomplete block design was used in order to complete the study before cows entered late lactation. Each cow was assigned a unique sequence of six of the eight treatlnents (diet x infusion combinations), for a total of 48 cow x period observations (Table 2). Each treatlnent was represented in each II-d infusion period. Treatments were arranged such that half of the cows were fed one of the two diets
TABLE 1. Composition of soybean meal (soy) and soybean meal plus com gluten meal (soy-gluten) experimental diets. Item
Soy
(% diet DM) -
Ingredient Com silage, % High moisture com. % Soybean meal, % Com gluten meal. % Vitamin and mineral premix, I % Analysis Dry matter, % Crude protein, % ADF, % Organic maner, %
Soy-gluten
74.3 8.4 14.5 0
74.3 9.6 8.6 4.3
2.8 100.00
3.2 100.00
X 45.2 14.2 21.1 91.0
SD 3.1 2 1.2 1.4 2.2
X 45.0 13.8 20.9 90.3
SD 3.1 1.5 1.5 2.4
lAs fed: Ca 15.9%, P. .7%, K 6.2%. Mg 2.2%, NaHC03 19.4, CI 10.6 ppm, Fe 265 ppm, Cu 132 ppm, co 3 ppm, Mn 1100 ppm, Zn 1323 ppm, I 44 ppm, S~ 5 ppm, vitamin A SO,OOO lU/lb, vitamin D 25,000 IU/lb, vltamm E 500 lU/lb.
AMINO ACID NUTRITION IN DAIRY COWS TABLE 2. Application of treaunents. 1 Period 2
2
3
4
5
6
3
4
2
7
5 8 6
7
4 3
6 5
7
eow3 A B
1
2
c4 04
2
1
4
3
1
8
~
5 8
6 5 8
7
4
I
6 5 8
2
4 3 2
F' G H
7 6
7
1 3
6 8 5 2 3 4 1
ITreatments 1 through 4 were waler (W), sodiwn caseinate (C), hydrolyzed casein, (HC), and methionine-lysine (ML) infusions when cows were fed the soy diet. Treatments 5 through 8 were W, C,HC. and ML infusions when cows were fed the soy-gluten diet. 2Periods were 11 d with periods 3 and 4 separated by a lQ-d interim for diet changes and adaptation. 3Cow H completed periods 1 to 3 only. 4eows samples for plasma amino acid analysis and rumen VFA.
during the first three infusion periods then fed the other diet during a lO-d interim and the remaining three infusion periods (Table 2). Blood and rumen samples were taken from four of the eight cows at the end of each period (description of sampling below). These four cows were equipped with duodenal cannula and were used for determination of digesta flow (to be reported separately). Treatments were arranged such that the four cows constituted an independent experimental group (Table 2) with three observations per diet x infusion treatment. One cow completed only three of the six periods due to low milk yield ( W (P W (P
