Synchronizing the availability of amino acids and glucose decreases fat retention in heavy preruminant calves.

Effects of synchronizing the availability of amino acids and glucose within a day on protein and energy metabolism were studied in heavy preruminant calves. Thirty-six preruminant calves (148 +/- 1.6 kg body weight) were assigned to 1 of 6 degrees of nutrient synchrony (SYN, 1-6) and to 1 of 2 meal sequences (i.e., the high-protein meal in the morning or in the evening). Calves at SYN 1 received 2 balanced meals: one at 0600 and one at 1800. Nutrient synchrony decreased stepwise from SYN 1 to SYN 6 in which calves received 85% of the daily protein supply in 1 meal. The digestible energy intakes at 0600 and 1800 were equal between treatments. Daily intakes of all nutrients and dietary ingredients were identical for all treatments. Calves were housed individually in respiration chambers. Apparent fecal nutrient digestibility and nitrogen and energy balances were measured. Apparent nutrient digestibility decreased when >71% of the dietary protein was fed in one meal. Nutrient synchrony did not affect the efficiency of digestible protein utilization in calves at a identical digestible nutrient intake. Heat production decreased from 691 to 629 kJ/(kg(0.75) x d) (P < 0.05) and energy retained as fat increased from 116 to 184 kJ/(kg(0.75) x d) (P < 0.01) with decreasing nutrient synchrony. Meal sequence did not affect any of the traits. In conclusion, synchronizing the availability of amino acids and glucose within a day did not increase the efficiency of protein utilization but substantially decreased fat retention in heavy preruminant calves.