摘要:
This trial was performed to examine the effects of different ruminally degradable starch levels on lac?tation performance, nutrient apparent digestibility and nitrogen balance of dairy cows fed high starch diets. Ten multiparous Holstein cows [(average lactation days: (214±38) d; average milk yield: (26.2±2.4) kg/d;average body weight: (727±65) kg] were randomly assigned to 2 groups, and each group had 5 dairy cows. Two types of diets with different ruminally degradable starch levels were formulated, one of them contained 62.3% ( percentage of total starch) ruminally degradable starch which named as low?ruminally degradable starch diet ( L?RDS) , and the other contained 72.1% ( percentage of total starch) ruminally degradable starch which named as high?ruminally degradable starch diet ( H?RDS) . A crossover experimental design was applied. There were two experimental periods, the transition period lasted for 7 d, and each period lasted for 21 d (14 d of pretrial period, and 7 d of sampling period). The results showed as follows:1) the apparent digesti?bility of starch and organic matter was significantly increased (P0.05). 2) Compared with L?RDS group, urinary urea?nitrogen and the proportion of urinary urea?nitrogen in nitrogen intake had a decrease trend for H?RDS group (P=0.09). The nitrogen intake, milk nitrogen, urinary nitrogen, fecal nitrogen, nitrogen retention and the proportions of them in nitrogen intake were not significantly affected by dietary ruminally de?gradable starch level (P>0.05), and the urinary excretion of purine derivatives and microbial protein yield were also not significantly affected by dietary ruminally degradable starch level ( P>0.05) . 3) Dry matter in?take, milk yield and milk composition of dairy cows were not significantly affected by dietary ruminally de?gradable starch level ( P>0.05) . Results of this study show that different ruminally degradable starch levels can affect the nutrient apparent digestibility of dairy cows fed high starch diets, with no significant influences on lactation performance and nitrogen balance.%本试验旨在研究饲喂高淀粉饲粮时不同瘤胃降解淀粉水平对奶牛泌乳性能、营养物质表观消化率和氮平衡的影响.选用10头荷斯坦经产奶牛[平均泌乳天数为(214±38)d,平均乳产量为(26.2±2.4)kg/d,平均体重为(727±65)kg]作为试验动物,随机分成2组,每组5头.试验设计2种不同瘤胃降解淀粉水平的试验饲粮,分别为瘤胃降解淀粉水平为62.3%(占总淀粉的百分比)的低瘤胃降解淀粉水平饲粮(L?RDS)和瘤胃降解淀粉水平为72.1%(占总淀粉的百分比)的高瘤胃降解淀粉水平饲粮(H?RDS).采用交叉试验设计,试验分为2期,过渡期7 d,每期试验21 d,其中适应期14 d,采样期7 d.结果显示:1)相比L?RDS组,H?RDS组有机物和淀粉的表观消化率显著升高(P0.05).2)相比L?RDS组,H?RDS组尿素氮及它们占摄入氮比例有降低趋势(P=0.09),摄入氮、乳氮、粪氮、尿氮和沉积氮及它们占摄入氮比例无显著变化(P>0.05),尿中总嘌呤衍生物排出量和微生物蛋白产量亦无显著变化(P>0.05).3)饲粮瘤胃降解淀粉水平对奶牛干物质采食量、乳产量和乳成分均无显著影响(P>0.05).综合以上结果可知,饲喂高淀粉饲粮时不同瘤胃降解淀粉水平影响饲粮营养物质的表观消化率,对泌乳性能和氮平衡无显著影响.