Nutritional parameters and productive performance of grazing sheep using castor bean cake as supplement or fertilizer

The objective was to evaluate the effect of detoxified castor bean replacing soybean meal in the concentrate diet or as nitrogen organic fertilizer replacing urea on intake and nutrient digestibility, blood parameters and productive performance of sheep finished on irrigated Tamani grass pasture under continuous stocking and variable stocking rate. The treatments were two concentrate diets: standard (ground corn and soybean meal) and alternative diet (ground corn and detoxified castor bean cake), and two nitrogen fertilizers: chemical (urea) and organic (fresh castor bean cake). The randomized complete block design was used in a 2 × 2 factorial arrangement with four replications (500 m² paddocks). Four sheep (2 castrated males and 2 females) were distributed in each experimental unit, totaling 64 animals with an average initial weight of 19.42 ± 3.6 kg. No effects (P > 0.05) were observed on the variables inherent to the evaluation of the pasture. The average stocking rate (SR) among treatments was 85.50 sheep/ha, equivalent to 9.87 Animal Units (AU)/ha. The alternative diet presented lower dry matter digestibility (62.71%), with no negative effects on nutrient intake and kidney parameters. Animals fed the standard and alternative diet showed average daily gain of 103.75 and 86.76 g/day, respectively. A finishing period of up to 100 days is recommended for sheep selected for production systems in semi-arid regions managed intensively on pasture. Detoxified castor bean cake did not alter nutrient intake, liver and kidney parameters of the sheep and can be used in pasture-based sheep farming.