Feeding value of nontoxic Jatropha curcas seed cake for partially replacing dry-rolled corn and soybean meal in lambs fed finishing diets

Abstract

The objective of this experiment was to determine the effects of partial replacement of dietary dry-rolled corn (DRC) and soybean meal (SBM) in isonitrogenous diets with different levels (0, 70, 140, and 210g/kg) of seed cake obtained from a nontoxic variety of Jatropha curcas on growth performance, dietary energetics, plasma metabolites, carcass characteristics, and visceral mass in 32 Pelibuey×Katahdin lambs. Jatropha seed cake (JSC) was obtained by mechanically pressing whole seed and contained 262g/kg crude protein (CP), 473g/kg neutral detergent fiber (aNDFom), 402g/kg acid detergent fiber (ADF), 7g/kg starch, 60g/kg ether extract, and 938g/kg of organic matter. The JSC substitution decreased linearly (P=0.02) final weight and average daily gain but did not affect (P=0.47) dry matter intake (DMI), thus efficiency of gain was decreased (P<0.01). In all treatments, the concentration of hemoglobin, haematocrit, glucose, creatinine, urea, and lipase was within normal ranges for healthy ruminants. Inclusion of JSC in diet did not affect dressing percentage and non-carcass fat deposition, but decreased (P=0.03) hot carcass weight and fat depth. As level of JSC inclusion increased, the muscle and fat composition of shoulder (as g/100g of shoulder weight) was affected, muscle increased (P<0.01) and fat decreased (P=0.02). Replacing corn and SBM with JSC did not affect empty body weight (EBW, as percentage of full weight) or the organ weights as a proportion of EBW (g/kg EBW). Increased JSC levels in the diet tended to increase visceral fat (P=0.06). The net energy (NE) value of JSC corresponds closely to its chemical composition (∼7.74MJ/kg NEm/kg), this NE value decreased linearly as the inclusion level of JSC increased as result of the removal of starch instead of NDF in diets and by the possible associative effects of JSC with other components of the diet. The changes of energy level and energy source (NDF and lipids instead of starch) by the replacement of corn and SBM by JSC, can affect the deposition of body fat. Based on DMI and performance observed in this study, nontoxic JSC is a suitable substitute for a portion of the DRC and SBM in a finishing diet; however, at high levels, it tends to decrease growth performance of lambs.