Effect of Protein Source, Autoclaving, and Lysine Supplementation on Gossypol Toxicity

Graded levels of free gossypol from cottonseed meats were added to corn-degossypolized cottonseed meal and corn-soybean meal diets for growing pigs. Solubility of the soybean nitrogen was reduced from 85% to 35% by autoclaving for 2 hours at 17 lb. of steam pressure. Solubility of cottonseed nitrogen was reduced from 87.4% to 79% by autoclaving for 30 minutes. Rate of gain of pigs fed the autoclaved meals was not significantly reduced. Addition of free gossypol at the levels of 0.03% and 0.036%, respectively, to both corn-cottonseed meal and corn-soybean meal diets resulted in depressed growth and death of the pigs. In a second study autoclaving degossypolized cottonseed meal for 3 hours at 17 lb. of pressure reduced growth of pigs from 1.26 lb. to 0.38 lb. per day. Addition of 0.2% of L-lysine resulted in growth almost equal to that of pigs receiving non-autoclaved meal (1.09 lb. per day). This was in the presence of 0.026% of added free gossypol. When the free gossypol level was increased to 0.036% of the diet, growth rate was reduced and four of six pigs died from gossypol toxicity. There was no evidence that addition of 0.2% of L-lysine to this high gossypol ration improved growth or reduced death losses.