Detoxification of Gossypol in Raw Cottonseed and the Use of Raw Cottonseed Meats as a Replacement for Soybean Meal in Diets for Growing-Finishing Pigs

Ratios of added iron to free gossypol in corn-raw cottonseed diets in the range of .5:1 to 1:1 reduced free gossypol level in the liver of rats enough to alleviate symptoms of toxicity (reduced feed intake, weight loss and eventual death). When iron to gossypol ratios within this range were used, rate of gain and feed efficiency were significantly superior to that obtained when ratios either higher than 1:1 or lower than .5:1 were used. Higher ratios of iron to gossypol 1.5 and 2:1 resulted in excessive amounts of dietary iron. It was observed that the use of warm water (50 C), in preparing the ferrous sulfate-cotton-seed meats mixture, improved the combination of iron and gossypol to the extent that free gossypol in the redried meats was reduced from 1.17 to .01%. The addition of propionic acid as a mold inhibitor apparently reduced the binding of gossypol and iron as evidenced by higher free gossypol values in cottonseed meats treated with a ferrous sulfate solution. However, liver residues of gossypol in rats were not affected by the presence of propionic acid in the diets in which the cottonseed meats were used. The substitution of uncooked and unextracted cottonseed meats (treated with ferrous sulfate) for soybean meal (in the range of 20 to 80% on an equal protein basis) was without effect on performance of growing-finishing pigs (25 to 90 kg). Accumulation of gossypol in the pigs livers was low and there was a trend for this level to be reduced as cottonseed level in the diet was increased (increasing dietary cottonseed level also increased total dietary iron since ferrous sulfate was added to the cottonseed meats at a 1:1 weight ratio to free gossypol).