Availability of Ruminally Undegraded Protein from Corn and Corn Gluten Meal

Abstract

Two N-balance trials were conducted using male Holstein calves weaned at the end of 6-week-old and made to maintain esophageal groove reflex after the weaning. Eight calves in Trial 1, or six calves in Trial 2, were respectively divided on halves into two groups, and used in a 2×2 Latin square experiment lasted for 4 weeks (two weeks per period) from 8 weeks of age. In each trial, rice straw and concentrate, which consisted mainly of corn and corn gluten meal (CGM) and contained 14% CP, were daily given to calves in proportion of 1:9 by weight at a level of 3% initial body weight in each period. The daily ration was divided into two equal quantities and fed at 8: 30 and 16: 30h. In Trial 1, N-balance was compared between the occasion when 20g L-lysine .HCl and 2g DL-methionine were daily administered in two equal portions through the esophageal groove immediately before each feeding, and the occasion when iso-nitrogenous L-glutamine was administered in the similar manner. In the result, the amount and the rate of N excretion into urine were significantly higher when glutamine was administered(P<0.01), but those of N retention were significantly higher when lysine and methionine were simultaneously administered (P<0.05). In Trial 2, N-balance was compared between the occasion when L-lysine. HCl was singly administered through the esopha-geal groove at a daily level of 0.333g/kg initial body weight in each period, and the occasion when iso-nitrogenous L-glutamine was administered. In the result, the amount and the rate of N excretion into urine were significantly higher when glutamine was administered (P<0.01), while those of N retention were significantly higher when lysine was administered (P<0.05 or P<0.01).
These results suggest that lysine would be the first or sole limiting amino acid for calves fed a diet consisted of corn and CGM, and further that the utilization of ruminally undegraded protein from corn and CGM could be improved by the rumen-bypassed administration of lysine.