Advances in the utilisation of castor (Ricinus communis Linneo) seed meal as protein supplement in poultry diets

In recent years, there has been increased interest in the use of readily available, cheap agroforestry products/by-products for livestock and poultry feeding. Castor is an economically important shrub grown mainly for its oils used for industrial, medicinal and food purposes. Castor seed meal (CSM), a by-product of castor oil extraction, has currently no food value but may have potential as feed ingredient in poultry diets. The increased demand for castor oil for industrial and medicinal uses will further increase the availability of this by-product. The meal has a good supply of protein (335–400 g/kg), metabolisable energy (7.65–11.34 MJ/kg), unsaturated fatty acids and moderate in essential amino acid content. The major factor hindering its efficient utilisation in poultry feed is the presence of highly toxic factors, mainly ricin. Currently, the meal is mainly, used as organic fertilizer. Several detoxification methods reduce the ricin content of the meal and make it safe for poultry. Moist heating, sodium chloride and lime treatments are more efficient in reducing the ricin content but dry heat has little effect. Detoxified meal is safe between 100 and 400 g/kg diet depending on the method of detoxification, age and species of poultry and amino acid supplementation but untreated meal is not. There is need for more research into processing conditions that would reduce toxicity and maintain a satisfactory nutrient profile. Recently, genetic engineering has been able to silence the ricin-coding gene in castor plant. Research into commercial production of this new cultivar will add value to castor meal as feed ingredient. Maximum utilisation of CSM in poultry feeding will reduce feed cost, provide additional source of income and maintain a balanced ecosystem by reducing the environmental risk of disposing this waste. This paper reviews the composition of CSM and developments in its utilisation for poultry feeding.