热应激条件下降低日粮粗蛋白含量和添加瘤胃保护赖氨酸对高产奶牛生产性能的影响

Effect of Reducing Dietary Crude Protein Content and Supplementing Rumen Protected Lysine on Performance of High Producing Dairy Cows under Heat Stress

观察降低日粮蛋白质(CP)和添加瘤胃保护赖氨酸(RPLys)对奶牛产奶量和奶组成的影响。60头荷斯坦奶牛随机分为4个试验组:饲喂18%CP和0.82%Lys的日粮为对照组,16.0%CP和0.65%Lys为试验1组,16.0%CP和0.85%Lys为试验2组,16.0%CP和1.05%Lys为试验3组。添加的Lys为瘤胃保护赖氨酸(RPLys),4个日粮配方用相同瘤胃未降解蛋白质来平衡。所有试验奶牛先饲喂2周试验日粮作为预试期,然后开始10周正试期。试验期间,最低和最高平均环境温度分别为(29.3±0.17)℃和(38.1±0.31)℃;最低和最高平均温湿度指数(THI)分别为73.7±0.30和83.7±0.21。对照组产奶量平均为(31.55±0.9)kg/d,与试验2组和3组的产奶量相似(P>0.05);对照组产奶量比试验1组高1.2 kg/d(P<0.05)。因此,如果奶牛日粮考虑代谢蛋白质(MP)的数量和质量,16%CP日粮在产奶后期和热应激条件下可以维持产奶量。RPLys添加到16%CP日粮改进MP质量,提高奶产量。血液葡萄糖、NEFA和BUN含量可能作为瘤胃微生物发酵和奶牛机体内牛奶合成所需均衡养分的参数。

A lactating trial was performed to characterize the effects of decreasing dietary CP from 18% to 16% and increasing dietary lysine from 0.65% to 1.05% with rumen protected lysine （RPLys） on milk yield and composition. Sixty Holstein cows were randomly allotted to four treatment groups and fed diets of 18% CP with 0.82% lysine or 16.0% CP or 0.65% lysine, 16.0% CP and 0.85% lysine or 1.05% lysine. Supplemental lysine was rumen protected and diets were balanced for the same intake of rumen undegradable protein（RUP）. The cows were fed the experimental diets for a two-week adaptation period followed by a 10-week lactation trial. During the study, the minimum and maximum ambient temperature averaged 29.3 ± 0.17 and （38.1 ± 0.31）℃. The minimum and maximum temperature-humidity index （THI） averaged 73.7 ± 0.30 and 83.7 ± 0.21. Milk production for control cows averaged （31.55 ±0.9） kg/d and was similar （P〉0.05） to treatment 2 or treatment 3 cows,but higher （P〈0.05） than treatment 1 cows by 1.2 kg/d. Thus if the amount and quality of MP is considered diets of 16% CP can maintain milk production in late lactation cows exposed to heat stress. RPLys can be supplemented to diets of 16% CP to increase MP quality and improve milk production. The blood glucose, NEFA and the BUN content may be used to evaluate rumen microbial fermentation and the milk synthesis in cow organism for the balance of required nutrients as the parameter.