Effects of varying degrees of synchrony of energy and nitrogen release in the rumen on the synthesis of microbial protein in cattle consuming grass silage

The effect of the degree of synchrony in the ruminal release of energy and nitrogen on microbial protein synthesis (MPS) was examined in cattle consuming grass silage (7.9 kg DM day−1) and a supplement of 1 kg day−1 of sucrose given as an intraruminal infusion. The sucrose was infused in three different patterns to induce varying degrees of synchrony of energy and nitrogen release. Four non-lactating cows received four experimental treatments in a 4 × 4 Latin square design with periods lasting 14 days. The treatments were (1) the basal diet of silage alone given in two equal meals each day at 10.00 and 22.00 h (BASAL), supplemented with (2) 1.0 kg sucrose given as a continuous infusion (CONT), (3) 1.0 kg sucrose given as two 6-h infusions starting at 10.00 and 22.00 h (SYNC) and (4) 1.0 kg sucrose given as two 6-h infusions starting at 16.00 and 04.00 h (ASYNC). The different patterns of infusing the sucrose altered (P < 0.05) the pattern of variation in ruminal concentrations of ammonia and the molar proportions of acetic and butyric acids at times during the interval between meals but none of the sucrose treatments resulted in any increase in the ruminal concentration of lactic acid. All sucrose treatments increased (P < 0.05) MPS relative to BASAL by, on average, about 23 g day−1. The increase in MPS for the SYNC and ASYNC treatments were identical at 20 g kg−1 sucrose. It is concluded that synchronising the rates of ruminal release of energy and nitrogen had no effect on MPS. © 1999 Society of Chemical Industry