APPARENT DIGESTIBILITY AND NUTRITIONAL VALUE OF UREA OR AMMONIA-SOLUTION-TREATED CORN SILAGES FOR LACTATING HOLSTEIN COWS AND MATURE SHEEP

Abstract

Corn silages were treated at harvest with 0.5% urea or 1.3–2.2% ammonia-molasses-mineral solution. Apparent recoveries of added nitrogen in the corn silages ranged from 95 to 100% in both experiments. Water-insoluble N and lactic acid contents were increased in the treated silages as compared to the control. Four diets containing either (1) grass-legume (GL) silage (38% DM) + medium grain (MG); (2) 0.5% urea-treated corn (CU) silage (31% DM) + MG; (3) 2.2% ammonia-treated corn (AC) silage (32% DM) + MG; (4) AC silage + low grain (LG) were fed to eight Holstein cows in a latin square design. Silage DM consumption, milk production and milk composition were not different (P > 0.05) among treatments. Reducing the level of grain feeding from 32 to 23% of the diet with ammonia-treated corn silage resulted in a decrease (P < 0.05) in total DM consumption, with no apparent effect on milk production or composition, at the levels of production observed in this study. There were significant (P < 0.05) differences among treatments in molar percentages of acetic, propionic and butyric acids in rumen fluid. However, no differences were observed in milk fat or solid nonfat contents of the cows receiving the four experimental diets. Sheep digestion studies carried out on the above silages indicated apparent digestibilities of DM, CP and energy were lower (P < 0.05) for the GL silage compared with the UC or AC silages (exp. 1), whereas there were no differences in apparent digestibilities of DM and energy of untreated corn silage or NPN-treated silages (exp. 2). However, crude protein digestion coefficient was lower (P < 0.05) for untreated corn silage compared with the three NPN-treated corn silages. The present studies failed to show a beneficial effect of treating corn silage with an ammonia, molasses and mineral solution rather than urea on silage fermentation and animal performance. Key words: Dairy cows, sheep, nitrogen balance, ammonia treatment, corn silage