Effects of 5′-uridylic acid feeding on postprandial plasma concentrations of GH, insulin and metabolites in young calves

Postprandial changes in plasma concentrations of GH, insulin, IGF-I, leptin and metabolites were compared between young Holstein bull calves fed with milk alone (control group) and with milk+5′-uridylic acid (UMP) (UMP group). UMP (2 g/day) was given with milk at 0830 h and 1530 h for 11 days from the 4th to the 14th day after birth. The perirenal fat weight was significantly lower in the UMP group than in the control group, but there was no significant difference in the weights of the liver, spleen and heart between the groups. Basal GH concentrations in the UMP group were slightly higher, but the postprandial increase in plasma insulin level and the area under the curve for insulin in the UMP group were significantly lower than those in the control group. There was no significant difference in IGF-I levels between the groups. In addition, the postprandial glucose concentrations were lower in the UMP group as reflected by the insulin level, and nonesterified fatty acid concentrations were not different. In the muscle (M. longissimus thoracis) sampled at 14 days of age, the triacylglycerol (TAG) content was significantly greater but glycogen content was significantly lower in the UMP group than in the control group. From these results, we have concluded that feeding 5′-UMP at 2 g/day for 11 days significantly alters TAG accumulation in the body and plasma concentrations of GH and insulin in young bull calves.