Relative toxicity of gossypol enantiomers in broilers

Use of cottonseed meal in poultry diets has been avoided in large part because of fear of gossypol toxicity. Gossypol exists naturally as a mixture of 2 enantiomers that exhibit different biological activities. Two experiments were conducted to determine the relative toxicity of gossypol enantiomers on broilers. In the first experiment, 3-d-old broilers were fed a standard diet containing 0, 100, 200, 300, or 400 mg of gossypol from gossypol acetic acid per kilogram of diet from 3 to 42 d of age. This form of gossypol contains both enantiomers in an equimolar ratio. Each dietary treatment consisted of 6 replicate pens of 4 birds. In the second experiment, 3-d-old broilers were divided into 15 pens of 4 birds each and fed a standard diet supplemented with either no gossypol or one of the gossypol enantiomers at 200 or 400 mg/kg of diet from 3 to 21 d of age. In both experiments, feed intake and BW gain were measured. In addition, several organ and tissue samples were collected at 21 d (experiments 1 and 2) and 42 d (experiment 1) of age and analyzed for gossypol. In experiment 1, feed consumption and BW gain were reduced (P < 0.05) at 21 and 42 d for the birds fed the highest level of gossypol. The concentration of gossypol in the heart, kidney, and plasma were equivalent at 21 and 42 d of age. In experiment 2, total feed consumption was reduced only in birds consuming (-)-gossypol, but BW gains were lower for birds fed either enantiomer. However, (-)-gossypol was more detrimental to growth than (+)-gossypol. The liver had the highest tissue concentration of both enantiomers, and accumulation of (+)-gossypol was higher than (-)-gossypol in all tissues examined. No racemization of the enantiomers was apparent in the tissues analyzed. Our results indicated that both gossypol enantiomers were toxic to broilers but that (-)-gossypol was more harmful to efficient broiler production than (+)-gossypol.