高产和低产奶牛不同泌乳阶段养分表观消化率、瘤胃发酵参数和乳品质的比较研究

Comparative study on apparent digestibility of nutrients,rumen fermentation parameters and milk quality of high-yielding and low-yielding dairy cows in different physiological periods

试验研究泌乳性能与泌乳阶段对奶牛养分表观消化率、瘤胃发酵参数和乳品质的影响。试验采用双因素试验设计,两个因素分别为泌乳性能(高产、低产)和泌乳阶段(泌乳前期、中期、后期)。将健康状况良好,体重、胎次、饲养管理相似的36头奶牛按泌乳性能和泌乳阶段分成6组,分别为高产泌乳前期组、高产泌乳中期组、高产泌乳后期组、低产泌乳前期组、低产泌乳中期组和低产泌乳后期组,每组6头牛。结果显示,高产奶牛瘤胃氨态氮(NH_(3)-N)、丙酸、异丁酸浓度以及干物质(DM)、粗脂肪(EE)和中性洗涤纤维(NDF)表观消化率显著高于低产奶牛(P<0.05),而瘤胃乙酸、丁酸浓度和乙酸/丙酸值显著低于低产奶牛(P<0.05)。奶牛泌乳后期瘤胃丁酸、异丁酸、异戊酸浓度和乙酸/丙酸显著高于泌乳中期(P<0.05),泌乳中期丙酸浓度显著高于泌乳前期和后期(P<0.05),泌乳前期戊酸浓度显著高于泌乳中期和后期(P<0.05)。泌乳中期DM、EE和酸性洗涤纤维(ADF)消化率显著高于泌乳后期(P<0.05)。高产奶牛乳脂率有低于低产奶牛的趋势,乳糖和乳蛋白率无显著差异(P>0.05)。研究表明,泌乳性能的提高可以改善奶牛的养分表观消化率,使瘤胃发酵模式偏向丙酸发酵;泌乳后期奶牛产奶量显著下降,但是乳脂率显著上升。

The experiment studied the effect of lactation performance and lactation stages on the apparent digestibility of nutrients,rumen fermentation parameters and milk quality of dairy cows.The experiment adopted a two-factor experimental design.The two factors were lactation performance(high yield and low yield)and lactation stage(prelactation,mid-lactation,and late-lactation).36 healthy dairy cows with similar weight,parity and feeding management were divided into six groups according to lactation performance and lactation stage,namely high-yield pre-lactation group,high-yield mid-lactation group,high-yield late-lactation group,low-yield pre-lactation group,and low-yield mid-lactation group and low-yield late-lactation group,with six cows in each group.The results showed that the content of rumen NH_(3)-N,propionic acid and isobutyric acid and the apparent digestibility of DM,EE and NDF in high yield dairy cows were significantly higher than those of low yield dairy cows(P<0.05),and concent of acetic acid,butyric acid and the ratio of acetic acid to propionic acid were significantly lower than those of low yield dairy cows(P<0.05).The concent of butyric acid,isobutyric acid,isovaleric acid and the ratio of acetic acid to propionic acid of late lactation stage were significantly higher than those in mid lactation stage(P<0.05),and the concentration of propionic acid in mid lactation stage was significantly higher than that in early and late lactation stage(P<0.05).The concentration of valeric acid in early lactation stage was significantly higher than that in middle and late lactation stage(P<0.05).The digestibility of DM,EE and ADF in mid lactation stage was significantly higher than that in late lactation stage(P<0.05).The milk fat rate of high yield dairy cows tended to be lower than that of low yield dairy cows,and there was no significant difference in rates of lactose and milk protein(P>0.05).The study indicates that the improvement of lactation performance can improve the apparent digestibility of nutrients in dairy cows and make the rumen fermentation mode is mainly propionic acid fermentation,and the milk production of dairy cows in late lactation period decreases significantly,but the milk fat rate increases significantly.