Effects of dietary concentrate-to-forage ratio on rumen fermentation and performance of dairy cows

Effects of dietary concentrate-to-forage ratio on rumen fermentation and performance were evaluated by using four primiparous Holstein cows with permanently ruminal cannula in a 4×4 Latin square design with four 20-d periods.Dietary concentrate-to-forage ratios were 30∶70,30∶70,50∶50,and 65∶ 35,respectively.The forage of the ration 1 was only Chinese wildryegrass hay.The forage of the ration 2,3,and 4 is comprised of Chinese wildryegrass hay,alfalfa hay,and corn silage.The results showed that: significant(P0.05) differences existed among four diets for rumen pH,the concentrations of ammonia N,total volatile fatty acids,propionate,and butyrate,and the ratios of acetate to propionate and acetate plus butyrate to propionate,but differences among them were not significant(P0.05) for acetate concentration;there were significantly difference(P0.05) for the yields of milk and 4% of fat corrected milk among four diets,showed no significant differences(P0.05) among them for milk contents of fat,protein,lactose,no fat solid and total solid.In addition,the yields of every composition increased with increasing of milk yield and significant(P0.05) differences existed among four diets.The results indicated that four diets with different concentrate-to-forage ratios could make rumen fermentation and milk compositions content stable though the concentrations of volatile fatty acids and milk yield were influenced and the appropriate association of forage with high and low quality could make rumen environment and milk fat content stable and improve performance.