胎次对中国荷斯坦牛305d产奶量及乳成分的影响OA

In order to accurately apply the dairy herb improvement(DHI)report and improve the lactation level of the whole herd,this experiment conducted variance analysis and correlation and regression analysis on 7 369 DHI records of Chinese Holstein cattle from a cattle farm in Ningxia to explore the effects of parity on 305 d milk yield and milk com-position.The results showed that the parity significantly affected the milk yield and milk composition of 305 d(P<0.01);305 d milk yield of the fourth fetus,milk protein rate of the second fetus,lactose rate of the first fetus,and urea nitrogen content of the seventh fetus were significantly higher than those of other parity(P<0.01);The milk fat percen-tage showed a trend of first decreasing and then increasing with the increase of parity,and the average milk fat percen-tage of the whole group remained above 3.57%;As the number of parity increases,there was a significant fluctuation in the number of somatic cells,with the sixth fetus reaching its highest value.Parity was significantly positively correlated with milk yield and somatic cell number(P<0.01),negative correlation with milk fat rate,milk protein rate,lactose rate,and total solid substance content(P<0.01);the milk fat rate was significantly positively correlated with the milk protein rate(P<0.01);milk protein rate was significantly negatively associated with the lactose rate(P<0.01),positive correlation with somatic cell number,blood urea nitrogen,and total solid substance(P<0.01);the number of somatic cells in milk was significantly negatively correlated with lactose rate and urea nitrogen content(P<0.01);BUN was sig-nificantly positively correlated with the lactose rate(P<0.01);lactose rate was significantly negatively correlated with milk fat rate,milk protein rate and somatic cell number(P<0.01);the total solid material content was significantly posi-tively correlated with milk fat rate,milk protein rate and lactose rate(P<0.01),and negative correlation with blood urea nitrogen(P<0.01).In summary,the influence of parity on milk production and composition in Chinese Holstein cattle follows a certain variation pattern,and it is suggested that the farm should adjust the dietary formula according to the changing trend,so as to improve the management level and economic benefit of the farm.