Effects of protected methionine and variable energysupply on lactational responses in dairy cows fedgrass silage-based diets

TL;DRAbstract

Twelve multiparous Holstein cows (average body weight 610 kg; 56 -84 d after calving at the start of the trial) in their second, third or fourth lactation were assigned to two-factorial (2 x 2) arrangement of treatments, in a balanced changeover design, involving two levels of energy (adequate, AE, 100% vs low, LE, 80% of INRA requirements) and two levels of ruminally-protected DL-methionine (Smartamine TM M: 0 vs 20 g/d). The treatments were M0-AE, M20-AE, M0-LE and M20-LE. The calculated intestinal concentrations of lysine and methionine (% PDI) were: 6.9 and 1.7, 6.9 and 2.1, 6.9 and 1.7, 6.9 and 2.2, respectively. The AE and LE diets contained (% DM): grass silage 44 and 50, and concentrates 56 and 50, respectively. Low energy intake was obtained by reducing the total amount of feed offered (from 19.6 kg DM in the AE diets to 16.2 kg in the LE diets). The diets provided 100% of requirements for protein digested in the small intestine (PDI). Average milk yield tended to be increased

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