Evaluation of castor (Ricinus communis) seed cake in the total mixed ration for sheep

BACKGROUND: Castor ( Ricinus communis ) seed cake (CSC), a byproduct of the vegetable‐oil industry, contains fairly good amounts of protein (crude protein, 290–390 g kg −1 ) which could be a suitable substitute of conventional oil cakes like soybean meal (SBM) in livestock diets but for the presence of a toxic glycoprotein, ricin. Efforts were, therefore, made to determine the feasibility of feeding CSC as such or after detoxification with lime (4%, wt/wt) by incorporating it into a total mixed ration (TMR) containing 65 and 35 parts ragi ( Eleucine coracana ) straw and concentrate mixture, respectively, with 11 g kg −1 CP and 50 g kg −1 TDN in which the SBM of a control diet was isonitrogenously replaced with either raw or lime‐treated CSC in test diets. The control and two test TMRs were fed to 24 sheep, respectively, divided at random into three dietary groups having equal number of animals for 150 days. RESULTS: Although lime treatment had a positive effect in reducing ricin by 58%, no adverse effect could be noticed by feeding raw or lime‐treated CSC in terms of body weight changes, macro‐ and micro‐nutrient utilisation, blood biochemical and mineral profile, rumen fermentation pattern, carcass traits, except the level of plasma immunoglobulins which was significantly ( P < 0.05) higher in sheep fed CSC diets. No pathological lesions could be noticed in the tissues of visceral organs due to feeding the raw or treated CSC. CONCLUSIONS: The findings suggest no adverse effect in the nutritional performance of adult sheep due to feeding the raw or treated CSC when incorporated into TMRs, probably due to a dilution of the ricin concentration or the development of immunity to the glycoprotein ricin, warranting long‐term growth‐cum‐production studies.