Effect of supplementation with groundnut cake and phosphorus on utilisation of millet stover by sheep and excretion of nutrients

Abstract

An experiment was conducted during the dry season in 1998 to determine the influence of supplementation with groundnut cake (GC) (0, 2.5, 5 and 7.5 g kg-1 LW) and phosphorus (P) (0 and 3 g day-1 animal) on diet and millet stover intake and digestibility, sheep growth rate and nutrient excretion. Total digestible organic matter intake (DOMI, g kg-1 LW 0.75) increased 4.24 (+ or -) 1.26 g per g of GC and decreased -0.31 (+ or -) 0.16 g per g GC2, and tended to increase (P = 0.10) with P supplementation. Millet stover intake (g kg-1 LW) was related to GC level by both linear (+1.79 (+ or -) 0.53 g per g GC) and quadratic (-0.20 (+ or -) 0.07 g per g GC2) functions and to P supplementation by linear function (0.87 (+ or -) 0.46 g per g P). No effect of GC X P interaction was observed. At equal level of GC, P supplementation increased stover intake by 2 to 20 %. Diet digestibility increased linearly (P < 0.01) with GC level, but no effect of P supplementation was observed. Digestibility of NDF was unaffected by either GC or P level. Animals supplemented with P had adequate P (0.24 %) in their diet in contrast with those unsupplemented (0.05 to 0.18 %). Live weight gain (g day-1) increased 22.10 (+ or -) 3.10 g per g GC and decreased -1.52 (+ or -) 0.39 g GC2. Live weight gain response to P supplementation (7.33 (+ or -) 1.66 g per of P) was independent of GC level. Nitrogen concentration in faeces (g kg-1 FDM) increased linearly both by GC and P supplementation, whereas urinary N (g l-1) was only influenced by GC level. Faecal P (g kg-1 FDM) increased about three-fold with P supplementation. It is concluded that an adequate capture of the additional N and P voided following supplementation could enhance the sustainability of mixed farming systems in the Sahel.