饲粮能量水平对干奶期奶牛瘤胃发酵、消化代谢及血浆生化指标的影响

Effects of Dietary Energy Levels on Rumen Fermentation,Digestion and Metabolism and Plasma Biochemical Parameters of Dairy Cows during Dry Period

本试验旨在研究饲粮能量水平对干奶期奶牛瘤胃发酵、消化代谢及血浆生化指标的影响。选择4头体重(BW)、体况评分(BCS)、预产期相近并装有永久性瘤胃瘘管的干奶期健康奶牛,采用4×4拉丁方设计,分别饲喂4种不同能量水平(产奶净能分别为5.46、5.78、6.11和6.43 MJ/kg DM)的饲粮。结果表明:随着饲粮能量水平的提高,干奶期奶牛瘤胃pH有降低的趋势(0.05<P<0.10),氨态氮含量有增加的趋势(0.05<P<0.10),丙酸含量显著增加(P<0.05),乙酸/丙酸显著降低(P<0.05);干奶期奶牛干物质表观消化率、粪尿氮总排泄量和氮沉积显著增加(P<0.05),氮利用率有提高的趋势(0.05<P<0.10),而中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)表观消化率以及粪尿氮总排泄量占摄入氮的比例有下降的趋势(0.05<P<0.10);干奶期奶牛血浆胰岛素含量显著升高(P<0.05),葡萄糖含量有升高的趋势(0.05<P<0.10),而非酯化脂肪酸含量显著降低(P<0.05)。由此可见,干奶期奶牛饲喂高能量水平饲粮可以促进采食,提高营养物质表观消化率、氮利用率和肝糖异生前体物质的产量,改善干奶期奶牛能量平衡状况。

The aim of this study is to investigate the effects of dietary energy levels on rumen fermentation,digestion and metabolism and plasma biochemical parameters of dairy cows during dry period.Four ruminally cannulated Holstein cows with similar body weight,body condition score and expected date of childbirth were used in a 4×4 Latin square design,and fed different energy levels(net energy for lactating were 5.46,5.78,6.11 and 6.43 MJ/kg DM,respectively)diets.The results showed that with the dietary energy level increasing,the rumen pH tended to decrease of dairy cows during dry period(0.05<P<0.10),the ammonia nitrogen content tended to increase(0.05<P<0.10),the propionate content significantly increased(P<0.05),and the acetate/propionate significantly decreased(P<0.05);the dry matter apparent digestibility,total nitrogen excretion of feces and urine and nitrogen retention of dairy cows during dry period significantly increased(P<0.05),the nitrogen utilization efficiency tended to increase(0.05<P<0.10),and the neutral detergent fiber(NDF)and acid detergent fiber(ADF)apparent digestibilities and ratio of total nitrogen excretion of feces and urine to nitrogen intake tended to decrease(0.05<P<0.10);the plasma insulin content of dairy cows during dry period significantly increased(P<0.05),the glucose content tended to increase(0.05<P<0.10),and the nonesterified fatty acids content significantly decreased(P<0.05).In conclusion,feeding high energy level diet for dairy cows during dry period can promote the feed intake,increase nutrient apparent digestibility,nitrogen utilization rate and hepatic gluconeogenesis precursor substances yield,and improve the energy balance of dairy cows during dry period.