Productive and metabolic parameters in lambs fed diets with castor seed meal

The objective of this study was to evaluate replacing levels of soybean meal with castor meal in diets for lambs on the productive and metabolic parameters. Fifty uncastrated Santa Inês lambs with an initial body weight of 26.52±4.76 kg and four-to-six months of age were confined in feedlots and fed diets containing castor seed meal (0, 25, 50, 75 and 100%) replacing soybean meal. The experimental design was completely randomized, with five treatments and ten replicates. The intakes of dry matter, organic matter, crude protein, ether extract, non-fibrous carbohydrates and total digestible nutrients decreased linearly (P<0.05), whereas the intake of neutral detergent fiber corrected for ash and protein, both in body weight or metabolic weight basis increased linearly (P<0.05). The digestibility coefficients of dry matter, organic matter, neutral detergent fiber corrected for ash and protein, non-fibrous carbohydrates, total carbohydrates and total digestible nutrients decreased linearly (P<0.05), and the digestibility of crude protein was not influenced (P>0.05). There was no effect (P>0.05) on the daily and total weight gains and feed conversion. Hepatic parameters were not affected. The consumed-, absorbed- and retained-nitrogen values decreased linearly (P<0.05), but had no effect on the liver metabolism. Despite the decreased intake, nutrient digestibility and nitrogen balance, castor seed meal can replace up to 50% of soybean meal without changing lambs' blood parameters or performance.