Effects of Different Levels of Whole Cottonseed in Diets on Rumen Fermentation for Beef Cattle

Three 7-year-old Simmental crossbred beef cattle(600±100 kg body weight) fitted with ruminal cannulas were used in a 3×3 Latin square design to investigate the effects of different levels of whole cottonseed in diets on rumen fermentation for beef cattle, and to make reference to optimum level of cottonseed in beef cattle diets.Three experimental diets contained (1) control(CT):basal diet; (2)middle level cottonseed(MC):13% cottonseed and (3) higher level cottonseed(HC): 25% cottonseed. The results showed that the mean pH of treatments MC, HC in a feeding period, decreased a little(-0.11,-0.09), compared with treatment CT.There were no differences among treatments in pH of the same time(P(0.05)). The mean NH_3-N of MC was the highest(7.01 mmol/L).Compared with treatment CT,the mean NH_3-N of treatment MC increased by 0.29 mmol/L, while treatment HC decreased by 0.07 mmol/L.The mean total VFA of treatment MC, HC increased by 7.4%,3.5%, respectively, compared with CT. The mean acetate concentration and propionate concentration of treatment MC, HC were higher than that of treatment CT too, while butyrate concentration and the ratio of acetate to propionate concentration were lower than it. There were significant differences among the mean values of A/P in three diets(P0.05), and the mean values were 4.49, 4.35, 4.05, respectively. The adding of whole cottonseed to beef cattle diet decreased the EDP of the nutrients in straw and cottonseed significantly(P0.05).