EFFECTS OF ENSILING UPON FREE AMINO ACIDS AND AMINES IN WHOLE-PLANT CORN, AND ON ITS SUBSEQUENT NUTRITIVE VALUE FOR LAMBS

In a replicated 2 × 2 double latin square, 16 lambs were fed whole-plant corn harvested at 26% or 38% dry matter (DM) and either ensiled or frozen. Corn was supplemented with urea (1.25%, DM basis). Voluntary intake was measured during a 17-day period of ad libitum feeding, after which the lambs were restricted on feed (65 g DM/W kg 0.75 ) for 14 days for the determination of nitrogen (N) balance and digestibility. Ensiling resulted in an increase in nonprotein nitrogen (NPN), mainly as amino acid-N, from 21% to 48% of the total N in the low DM corn, and from 25% to 43% in the high DM corn. Basic and acidic amino acids were selectively degraded during ensilage. Amine-N accounted for less than 5% of total N in the silages. Voluntary intake (g DM/W kg 0.75 ) of ensiled corn was not significantly different from that of frozen corn (77.3 vs. 81.7) but was higher (P < 0.05) for the low DM than the high DM corn (85.1 vs. 73.9). Estimates of N balance and digestibility of DM and organic matter were not affected (P < 0.05) by ensiling or by stage of harvest. There appears to be no adverse effect of ensiling whole-plant corn on its voluntary intake and N utilization by ruminants, provided the silage is supplemented with urea. Key words: corn, ensiling, intake, Digestibility, ruminants, nonprotein nitrogen