Effect of N-acetyl-l-methionine supplementation on lactation performance and plasma variables in mid-lactating dairy cows

摘要

The objective of current study was to investigate theeffect of N-acetyl-l-methionine (NALM) supplementationon lactation performance and plasma variables inmid-lactating dairy cows. Forty-eight multiparous cowswere blocked into 12 groups based on parity, days inmilk, and milk production and were randomly assignedto 1 of the 4 treatments: 0, 15, 30, or 60 g/d of NALMper cow to supplement the basal diet. The experimentwas conducted over a 13-wk period, with the first weekas adaptation. The yields of milk, fat-corrected milk,and milk lactose were increased quadratically, andenergy-corrected milk yield tended to increase withincreased NALM supplementation in a quadratic manner.The dry matter intake, milk protein yield, milk fatyield, contents of milk composition (protein, fat, lactose,total solids, and milk urea nitrogen), feed efficiency,and body weight change were not affected by NALMsupplementation. In addition, plasma methionine concentrationwas increased quadratically, and proline, totalnonessential AA, and total AA concentrations weresignificantly higher in the 30 g/d group compared withthat of the control group. However, other AA and totalessential AA concentrations were not affected withsupplementation of NALM. Adding NALM increasedconcentrations of total protein and globulin in plasma,but decreased plasma urea nitrogen concentration in aquadratic manner. Meanwhile, plasma malonaldehydeconcentration decreased linearly as doses of NALM additionincreased. Our results suggested that the supplementationof NALM improved milk yield and proteinsynthesis in the liver, and lowered lipid peroxidation inmid-lactating dairy cows.