Improving productivity and reducing methane production and N and phosphorous excretion in lambs through nutritional strategies. I. Pre-treatment

A series of trials were conducted to evaluate the effect of ammonium bicarbonate pre- treatment on nutritive value of soybean hull and to compare the performance of growing sheep offered pelleted untreated (USH) and ammoniated soybean hull (ASH) at different ratios to concentrate. In trial 1, the soybean hull was first pre-treated with ammonium bicarbonate. Three pelleted soybean hull-based diets were formulated with different ratios of concentrate mixture: (1) 60% USH and 40% concentrate (USH60), (2) 60% ASH and 40% concentrate (ASH60), and (3) 70% ASH and 30% concentrate (ASH70). Nutritive value was evaluated by in vitro gas test. Neutral detergent fibre (NDF) of soybean hull was reduced by 4.7% (P < 0.01), and N (N) content increased by 70.1% (P < 0.01) by ammonification. Compared to the USH, gas production and estimated in vitro organic matter digestibility (IVOMD) of ASH were significantly improved (P < 0.01). The IVOMD was significantly higher (P < 0.01) in diet ASH60 than that in USH60 and ASH70. Rate constant of digestion was lower in USH60 than that in the two ASH-based diets. In trial 2, twenty-seven growing Huzhou lambs (Body weight?) were randomly divided into three groups, and allocated to one of the three diets: USH60, ASH60 and ASH70. Feed intake, average body gain and feed conversion ratio were significantly higher (P < 0.01) in ASH60 than in USH60. In trial 3, manures from trial two was gathered and manures from each pen divided into 2, one covered with polyethylene and the other without. Nitrogen content of the manures from ASH60 animals was the highest, followed by USH60, with the lowest N for ASH70, indicating that lower concentrate in the diet may reduce the N excretion in manure. After composting, N content in the covered treatments tended to be higher than that in the uncovered. The recovery of N was significantly (P < 0.01) higher in the covered compared to the uncovered manures. Cover treatment did not have significant effect on P recovery. These results suggest that pre-treatment with ammonium bicarbonate could improve the nutritive value of soybean hull and increase the growth potential in lambs. Nitrogen loss during composting could be reduced by covering the manure with plastic. (author)