Effects of Isoacids Supplementation in Different Forage to Concentrate Ratio Diets on Rumen Fermentation in Vitro

This study was conducted to examine the effects of different forage to concentrate ratios and isoacids supplementation on rumen fermentation in vitro.The rumen fluid was collected from four castrated Nanjiang brown goats [(25.48±1.51) kg] fitted with permanent rumen fistulas.The trial was carried out using fermentation in vitro with the combinations of three forage to concentrate ratios(30∶ 50,50∶ 50 and 70∶ 30) and two isoacids concentrations(0 and 1%) in a two factorial arrangement.The results showed that after 24-hour fermentation in vitro,without isoacids supplementation,with the ratio of concentrate increased,the ruminal pH,NH3-N concentration,the ratio of acetate to propionate and the ratio of acetate to total volatile fatty acid(TVFA) were significantly decreased(P0.05),but gas production,concentrations of acetate,propionate,TVFA,and the ratio of propionate to TVFA were increased significantly(P0.05).When isoacids were added in 30∶ 70 group,there was a significant rise in concentrations of acetate,propionate and TVFA(P0.05),but no significant influence on pH,gas production,concentrations of NH3-N,microbial protein(MCP),butyrate(P0.05).When isoacids were added in 50∶ 50 group,the NH3-N concentration was significantly dropped(P0.05),however,gas production,concentrations of MCP,acetate,propionate and TVFA were increased significantly(P0.05),there were no significant effects on pH,butyrate concentration and the ratio of acetate to propionate(P0.05).When isoacids were added in 70∶ 30 group,the NH3-N concentration was significantly decreased(P0.05),there was a significant increase in gas production,concentrations of MCP,acetate,propionate and TVFA(P0.05),and no significant influence on pH and the ratio of acetate to propionate(P0.05).In conclusion,isoacids can increase the digestibility of organic matter and the utilization of NH3-N and enhance the synthesis of MCP,acetate,propionate and TVFA,and in this experiment,with the ratio of concentrate increased,the effects of isoacids supplementation are better.