Effect of Gossypol on the Rumen Microbial Degradation of Whole Cotton Seed and Grass Hay Incubated in Consecutive Batch Cultures

It is well known that cottonseed is widely used as a feed supplement for ruminant animals. However, anti-nutrient gossypol in the seed of cottonseed may cause adverse effects on microbial degradation of the feed. An experiment was conducted to investigate the effects of gossypol on the rumen microbial degradation of whole cottonseed (WCS) and grass hay (GH) with and/or without antinutrient gossypol in a consecutive batch culture (CBC) system. The results obtained from this experiment suggest that the presence of gossypol (1 mM) inhibits dry matter (DM) degradation, gas production from grass hay (GH), and growth of rumen microorganisms in consecutive batch cultures. There was a change in the molar proportion of volatile fatty acids (VFA) when WCS was used as a substrate, suggesting the fermentation of WCS has altered the composition and the activity of the rumen microbial population. However, GH with 1 mM gossypol was still more degradable by mixed rumen microorganisms than WCS, and there was evidence that the microorganism might adapt to the presence of gossypol when GH was the substrate, but not when WCS was used.