Effect of rumen-protected methionine and lysine on casein in milk when diets high in fat or concentrate are fed.
To examine the effect of supplying methionine and lysine on milk N composition, isoenergetic, isonitrogenous diets containing 50:50 with 3.9% added fat or 25:75 forage to concentrate with no added fat were fed with or without rumen-protected methionine and lysine to four primiparous and four multiparous early lactation (36 d in milk) Holstein cows in two 4 x 4 Latin squares. Diets contained 1.7 Mcal NE1 and were fed for ad libitum intake. Periods were 21 d. Rumen-protected methionine and lysine increased total N and casein N percentage with the 3.9% fat, but did not increase total N and casein N percentage with the diet without fat. Whey N percentage was greater with the no fat than with the 3.9% fat diet. Whey N percentage was not affected by adding amino acids. Nonprotein N percentage was greater for the diet with the 3.9% fat than with no fat. Proportions of casein N or whey N to total N were unaffected by treatments. Adding methionine and lysine to diets did not increase yields of total N and casein N. The 3.9% fat diet increased proportions of long-chain (C18:0 and C18:1) and decreased proportions of short- to medium-chain fatty acids (C8 to C16) in milk fat. Plasma nonesterified fatty acids and triglyceride concentrations were greater with the 3.9% fat as compared to the no fat diet. Methionine and lysine decreased plasma triglyceride concentrations with the 3.9% fat diet. Milk yields, DM intakes, and plasma glucose concentrations were unaffected by treatment.
Chow
J M
JM
Department of Animal Science, University of California, Davis 95616.
DePeters
E J
EJ
Baldwin
R L
RL
D000821:Animal Feed; D000818:Animals; D002364:Caseins / Q000032:analysis*; D002417:Cattle / Q000378:metabolism*; D004032:Diet; D004041:Dietary Fats / Q000378:metabolism; D004063:Digestion; D005260:Female; D007774:Lactation; D008239:Lysine / Q000494:pharmacology*; D008715:Methionine / Q000494:pharmacology*; D008892:Milk / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis
D002364:Caseins; D004041:Dietary Fats; D008715:Methionine; D008239:Lysine; D009584:Nitrogen