Comparative Assessment Of Nutrient Composition And In Situ Ruminal Degradation Of Main Forage For Dairy Cow

This experiment was conducted to investigate the chemical compositions and in Sacco degradability of main forage for dairy cow.It can update the data of dry matter(DM),crude protein(CP),neutral detergent fiber(NDF)and acid detergent fiber(ADF)in forage for the new edition of Chinese Dairy Cattle Nutrient Requirements and provide references when making formulas for dairy cows.Nineteen kinds of forage,including alfalfa silage,whole-plant wheat silage,oat silage,Zhengdan 958 corn silage,Jingke 516 corn silage,Anderson alfalfa,Ameristand 201+z alfalfa,Golden Empress alfalfa,Zhongmu No.1 alfalfa,Gongnong No.1 alfalfa,imported oat hay,Danyan 111 oat hay,Leymus chinesis,peanut vine,barley plant,naked oat straw,millet straw,wheat straw and rice straw were collected.The nutrient compositions were determined by chemical analysis and nylon bag technique was used to assess rumen degradability.Alfalfa silage(20.39%)and Ameristand 201+z alfalfa hay(20.23%)possessed high CP(crude protein),and were significantly higer than that of the others.While the content of CP of agricultural byproducts were low,among which wheat straw was the lowest(3.05%).NDF content of forage of byproducts ranged from49.98% to 83.62%.Silage and hay contained 41.93% to 64.97% of NDF,among which Ameristand 201+z alfalfa hay was the lowest.Fodders from byproducts contained higher ADF(35.87%～54.03%),while ADF in silage was lower(30%).2 kinds of whole-plant corn silages were significantly higher in starch,among which Zhengdan 958 corn silage was the highest(27.86%).The fraction of slowly degraded of NDF was the highest in silage,and its fraction of immediately degraded of DM,CP and ADF(30.76%、38.98% and 3.17%)was also the highest.The rate of fraction of slowly degraded of DM,CP,NDF and ADF(0.063%、0.069%、0.055% and 0.051%)was the lowest in hay,while its fraction of slowly degraded of DM,NDF and ADF(41.94%、47.73% and 47.32%)were the lowest.The fraction of slowly degraded and effective degradability(ED)of DM,CP,NDF and ADF was the lowest in byproducts.The ED of starch for whole-plant wheat silage(95.45%)was higher than other silages,while Jingke 516 corn silage(86.80%)was the lowest.Strong correlation was found between ED and rumen digestibility of 36 h in silage.The correlation between ED and rumen digestibility of 24 h in hay was strong.There was a strong correlation between effective degradability and dynamic degradability of starch at 8 h,which can be used to determine starch degradability of silage in the rumen of dairy cows.In conclusion,silage and afalfa are ideal forage for cows,since they are low in fiber,rich in CP and easy to digest.Forage from byproducts is poor in nutrient quality and digestibility because of high fibre and low CP,but its nutritive value can be improved by appropriate processing.