Abstract
Effects of the pattern of energy supply on the efficiency of nitrogen utilization for microbial protein synthesis (MPS) were examined in cows consuming grass silage (7.1 kg DM/d) and supplement of 1 kg sucrose per day given as an intraruminal infusion. Three non-lactating cows received three experimental treatments in a $3{\times}3$ Latin square design with each period lasting 14 days. The treatments were (1) the basal diets of silage alone given in one meal each day at 09:30 h (BASAL), supplemented with (2) 1.0 kg sucrose given a 4-h infusion starting at 09:30 h (SYNC), (3) 1.0 kg sucrose given a continuous infusion for 24 h (CONT). Compared with BASAL, sucrose infusions altered (p<0.05) the pattern of variation in ruminal pH and the concentration of ammonia at 4 h after feeding but none of the sucrose treatments resulted in any changes in the ruminal concentration of VFA. All sucrose treatments increased (p<0.05) MPS relative to BASAL by 14% and 33% for SYNC and CONT, respectively, and that for CONT was greater (p<0.05) than for SYNC. It is concluded that synchronization of energy and nitrogen over the shorter term has no further advantage of the efficiency for MPS relative to CONT.