EFFECTS OF PHYSICAL FORM OF CORN AND UREA SUPPLEMENTATION ON THE PERFORMANCE OF MALE HOLSTEIN CALVES

Abstract

Diets of corn and corn silage (80:20 dry matter (DM) basis) were fed to 48 male Holstein calves in an experiment of 2 × 2 factorial design to evaluate the effect of rolling or grinding corn and of the addition of 0 or 1.2% urea. The calves were fed for 105 days and had an initial weight of 92.6 kg. The physical form of the corn had no effect on performance of the calves. The inclusion of urea increased dietary protein from9.5to 12.8% and growth rate (P < 0.05) from 0.72 to 1.06 kg/day and improved feed efficiency (P < 0.05) from 4.68 to 3.69 kg feed DM/kg gain. Digestibilities of DM and N were increased by urea supplementation (P < 0.05) but not affected by the physical form of the corn (P > 0.05). In a subsequent experiment, the effects of physical form of corn and urea supplementation on rumen volatile fatty acids and ammonia and plasma urea were examined in calves. The physical form of the corn had no effect (P > 0.05), whereas urea supplementation increased rumen ammonia (P < 0.05) and reduced pH (P < 0.05). The only volatile fatty acids affected by treatments were propionate and butyrate which were increased (P < 0.05) and decreased (P < 0.05), respectively, on the urea-ground corn combination. The results indicate that with 100- to 200-kg growing calves, rolled or ground corn was equally well-utilized when fed with 20% corn silage and that with urea as the only supplementary source of N, growth rates of 1 kg/day were achieved.