Effect of Complexing Sodium Bentonite with Soybean Meal or Urea in Vitro Ruminal Ammonia Release and Nitrogen Utilization in Ruminants

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Abstract
Five in vitro rumen ammonia release experiments were conducted with combinations of nitrogen (N) sources and sodium bentonite (NaB). The first experiment demonstrated that complexes of NaB with either casein or soybean meal (SBM) resulted in reduced ammonia release. Urea (U) treated with NaB exhibited reduced ammonia release at 4 hr, but not at 24 hr of incubation. Further experiments showed that as the ratio of protein to NaB widened ammonia release increased. A SBM:NaB mixture that had been wetted and dried was more effective in reducing ammonia release than simply dry mixing the ingredients. Varying the pH of the water used in mixing SBM with NaB had little effect on ammonia release. A 3 × 2 factorial N balance trial was conducted (3 N sources, with and without NaB) to determine the N utilization of lambs fed high roughage diets supplemented with SBM, SBM + NaB, U, U + NaB, SBM + U and SBM + U + NaB. SBM treated with NaB with or without U resulted in nonsignificant increases in N retention. NaB significantly reduced ruminal ammonia concentration at 2 and 4 hr, but not at 1 hr postfeeding. A performance trial with individually-fed lambs tested the supplemental N sources of SBM, U, SBM + U, SBM + NaB (3:1 ratio) SBM + NaB (3:1 ratio) + U and SBM + NaB (1.5:1 ratio) + U. The SBM-supplemented lambs gained more and were more efficient than those supplemented with U. The SBM + U-fed lambs were intermediate between those fed SBM or U treatments. SBM treatments complexed with NaB, whether alone or in combination with urea, gained as rapidly and were as efficient as the SBM control. Steers supplemented with SBM + NaB + U gained more (P<05) than those fed SBM + U in a 112-day growing trial. These data show that complexing protein with NaB has a positive effect on N utilization in ruminants. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.