Production, Management, and the Environment 3

摘要

Methionine is the first limiting amino acid for milk and protein productionin lactating dairy cows fed corn-based diets. A field trial wasconducted in a commercial dairy farm in Northeast Spain with the aimto evaluate the effect of supplementing a rumen-protected methionineproduct (Timet; Vetagro S.p.A.; Reggio Emilia, Italy) on lactationperformance in high-yielding dairy cows. Ninety-nine multiparousHolstein cows were used in a 3-period switchback design: Control 1(CTR1, 21 d), Timet (TMT, 21 d) and CTR2 (12 d). All the cows thatentered the study were between 0 and 120 DIM. Cows were fed a TMRformulated to provide 16.7% CP, 29% starch, and 32% NDF with 2793g/d of MP and Lys:Met 2.93. During TMT treatment, Timet (55% ofDL-Methionine) was supplemented 25 g/d per head. Milk yield wasrecorded daily and milk was sampled for protein, fat, and urea every2 d. Data were analyzed using MIXED model ANOVA including cowas random effect (JMR pro 13). Although there was not significant differencein milk yield, milk protein was significantly increased by TMT(3.43%) compared with CTR1 (3.35%) and CTR2 (3.38%) (P < 0.05),and milk fat was also significantly increased by TMT (3.75%) comparedwith CTR1 (3.63%) and CTR2 (3.71%) (P < 0.05). During TMT treatmentit was possible to observe a trend in lowering milk urea (180.8mg/L) compared with CTR1 (193.0 mg/L) and CRT2 (189.9 mg/L) (P= 0.43). In conclusion, addition of Timet to a corn-based diet increasedmilk protein and fat concentration.