泌乳天数对头胎和经产荷斯坦牛生产性能的影响及相关性分析

Effects of Days in Milk(DIM) on Production Performance and Correlation Analysis in Primiparous and Older Holstein Cows

本试验收集了内蒙古地区某牧场4 156头荷斯坦泌乳牛共20 441条生产性能测定记录,采用SPSS17.0软件对不同泌乳阶段头胎牛和经产牛的产奶量、乳脂率、乳蛋白率、体细胞数(分)、尿素氮含量进行了分析,结果表明,头胎牛和经产牛产奶量在泌乳周期内均先升高后降低,60~100d时均达到高峰,经产牛高峰奶高于头胎牛,持续力小于头胎牛。乳脂率均呈先降后增趋势,产奶高峰期(60~100d)降到最低;高峰期以前头胎牛大于经产牛,高峰期过后头胎牛小于经产牛。乳蛋白率在整个泌乳周期内均持续增加,且经产牛大于头胎牛。经产牛体细胞分在泌乳期内持续增加,头胎牛在泌乳早期(小于60d)和泌乳后期(大于400d)体细胞分较高,中期(泌乳100d左右)最低;泌乳早期头胎牛体细胞分高于经产牛,泌乳中后期经产牛高于头胎牛。头胎牛尿素氮含量在泌乳早期和后期较高,泌乳中期较低,经产牛泌乳早期和后期较低,泌乳中期(100~200d)最高;小于300d时经产牛高于头胎牛,超过300d时头胎牛高于经产牛。在整个泌乳周期内,头胎牛与经产牛产奶量、乳脂率和乳蛋白率均有显著相关性(P<0.05),体细胞分和尿素氮无显著相关性(P>0.05)。

In order to evaluate the infuence of days in milk（DIM） on production performance in primiparous and older Holstein cows, a total of 20441 DHI records of 4156 cows were collected on a dairy farm in Inner Mongolia. The index were analyzed such as milk yield, butterfat（F%）, lactoprotein percentage（P%）, somatic cell score（SCC） and urea nitrogen （MUN） in primiparous and older cows, as well as correlation between the two using SPSS 17.0 in the study. As a result, frstly, milk yield increased and then decreased with the increase of lactation days, peaked on 60 to 100 days after parturition. The peak milk of older cow was greater and sustainability was less than primiparous. Secondly, in both of primiparous and older cows, butterfat percentage（F%） decreased and then increased with the increase of days in milk（DIM）,minimized at the peak of lactation （60 to 100 days after parturition）. Comparing between primiparous and older cows, F% of primiparous was higher before the peak of lactation, while lower after the peak of lactation than the olders. Thridly, lactoprotein percentage（P%） of both primiparous and older cows increased steadily with days in milk（DIM）, and the older was higher than primiparous all the time. Fourthly, SCC of older cows increased steadily with days in milk（DIM）. SCC of primiparous was higher during early lactation（within 60 days in milk）and the end of lactation （more than 400 days）, minimized during the medium term of lactation（around 100 days of lactation）. Comparing between primiparous and older cows, SCC of primiparous was higher in during early lactation, while less in the middle and end of lactation than older cows. Fifthly, MUN of primiparous was higher in the early and end of lactation than the medium term. On the contrary, MUN of older cows was less in early and the end of lactation than the medium term. Comparing between primiparous and older cows, MUN of older cows was higher within 300 days in milk, less for more than 300 days than primiparous. In the whole lactation period, the correlations of milk yield, F% and P% were signifcant between primiparous and older cows（P〈0.05）, while the correlations of SCC and MUN were not signifcant between the two groups （P〉0.05）.