|Dowd, Michael - Mike|
Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/5/2005
Publication Date: 9/1/2005
Citation: Lordelo, M.M., Davis, A.J., Calhoun, M.C., Dowd, M.K., Dale, N.M. 2005. Relative toxicity of gossypol enantiomers in broilers. Poultry Science. 84(9):1376-1382. Interpretive Summary: Gossypol, a polyphenolic pigment found in cottonseed in both a (+)-form and a (-)-form, was added to poultry meals to study the compound's antinutritive effect on broiler production. Feeding experiments were conducted with (+)-gossypol, (-)-gossypol, and with a 50/50 mixture of the two forms. Feed consumption, bird weight, and the levels of gossypol in various animal tissues were determined after 3 and 6 weeks of feeding. High concentrations of either form reduced bird weight, although only the (-)-form significantly reduced feed consumption. The (+)-form was found in higher concentrations in the animal tissues that the (-)-form. In addition, interconversion of the two forms was not observed. The results indicate that both forms of gossypol affect animal growth but that the (+)-form is much less antinutritive that the (-)-form and suggests that cottonseed containing low levels of (-)-gossypol may be acceptable in poultry feed in limited amounts. The results should be of interest to poultry producers and researchers working to incorporate cottonseed and cottonseed meal into poultry rations.
Technical Abstract: Use of cottonseed meal in poultry diets has been avoided in large part because of the fear of gossypol toxicity. Gossypol exists naturally as a mixture of two enantiomers that are known to exhibit different biological activity. Two experiments were conducted to determine the relative toxicity of these gossypol enantiomers on broilers. In the first experiment, 3-d-old broilers were fed a standard diet containing either 0, 100, 200, 300 or 400 mg of gossypol (from gossypol acetic acid) per kg of diet. This form of gossypol contains both enantiomers in an equimolar ratio. Each dietary treatment consisted of six replicate pens of four birds. In the second experiment, 3-d-old broilers were divided into 15 pens of four 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. In both experiments, feed intake and bird weight (BW) gain were measured. In addition, several organ and tissue samples were collected at 21 d (experiments 1 and 2) and at 42 d (experiment 1) of age and were 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 only reduced in the 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. Racemization of the enantiomers did not occur in the tissues analyzed. The results indicate that both gossypol enantiomers are toxic to broilers, but that (-)-gossypol is more detrimental to efficient broiler production than (+)-gossypol.