RESUMEN
Effects of S fertilization, 0 or 138 kg of S/ha, as (NH4)2SO4 on chemical composition, ensiling characteristics, and utilization of sorghum (Sorghum bicolor L.) silage by wether lambs was investigated. Pioneer 947' sorghum forage was ensiled at the soft dough growth stage. Sulfur fertilization increased (P < .01) concentrations of S, N, K, Mn, and water-soluble carbohydrates (WSC) and decreased (P < .05) concentrations of Fe, Cu, Al, and acetic acid after ensiling. Sulfur-fertilized sorghum silage (N:S = 12) and non-S fertilized silage (N:S = 15) were fed alone and supplemented with urea to achieve 14% CP (N:S = 18 and 23, respectively) to 24 crossbred (1/2 Dorset, 1/4 Finn, 1/4 Rambouillet) wether lambs in a metabolism trial. Sulfur fertilization decreased apparent lignin digestibility and increased apparent digestibilities of DM, NDF, and hemicellulose (P < .05), apparent absorption and retention of S, N, P, K, Mg, and Mn (P < .01), and apparent absorption of Ca (P < .05). Apparent absorption and retention of Cu and Al were lower (P < .05) in lambs fed the S-fertilized silages. Digestibilities of DM and NDF were increased by N-supplementation in the non S-fertilized silage (N x S interaction, P < .05). Nitrogen supplementation increased (P < .01) blood urea nitrogen and apparent absorption and retention of N. Results indicate that S fertilization enhanced forage quality primarily due to increased TNC concentration, digestibility of hemicellulose, and N utilization by lambs but could exacerbate Cu deficiency where Cu levels are marginal.