胎次和产奶量对奶牛泌乳性能的影响

【目的】明确高产与低产奶牛胎次对产奶量、乳成分和泌乳持续力的影响,为优化奶牛场的饲养管理模式及提高奶牛使用年限提供理论依据。【方法】基于北京、河北等地17个奶牛养殖场共12406头荷斯坦奶牛2021年春季的生产性能测定(DHI)报告,按高产(48.69±6.88 kg/d)和低产(23.47±5.28 kg/d)进行分组,对原数据经预处理后获得5158头高产奶牛和3110头低产奶牛的DHI报告;采用单因素方差分析(One-way ANOVA)进行方差齐性检验,通过Pearson双侧检验进行多变量相关分析,并以LDS和Duncan's多重比较对组间差异进行分析,2个变量间的相关性则通过Spearson相关系数进行判断。【结果】不同胎次对高产与低产奶牛的产奶量、乳成分和泌乳持续力均有影响:高产奶牛3胎和4胎的日产奶量显著高于其他胎次(P<0.05,下同),4胎以上高产奶牛的牛乳体细胞数(SCC)显著高于1胎和2胎高产奶牛;低产奶牛1胎的日产奶量、乳糖率显著高于其他胎次,且SCC显著低于除2胎外的其他胎次。在奶牛泌乳持续力方面,1胎高产奶牛的泌乳持续力显著高于3胎、4胎和5胎,1胎低产奶牛的泌乳持续力显著高于其他胎次,其他胎次间的泌乳持续力均无显著差异(P>0.05,下同);高产与低产奶牛的泌乳持续力与SCC间无显著相关性,但与日产奶量显著相关。除干物质含量与日产奶量、乳脂率与乳糖率的相关性外,高产奶牛和低产奶牛的产奶量、乳成分及SCC间的相关性基本一致,其中,日产奶量与乳糖率呈极显著正相关(P<0.01,下同),与SCC呈极显著负相关,而SCC与乳脂率和乳蛋白率均呈极显著正相关。【结论】高产奶牛最佳使用胎次为3~4胎,低产奶牛最佳使用胎次为1~3胎;高产与低产奶牛的胎次均影响其产奶量、乳成分及泌乳持续力,但不同胎次下产奶量和乳成分的变化趋势存在一定差异。因此,在提高饲养管理水平的基础上,应进一步优化营养供给,及时调整饲粮配方,合理对奶牛进行分群和规划,以达到奶牛的最佳使用胎次,增加养殖经济效益。

Effects of parity and milk yield on lactation performance of dairy cows

【Objective】To explore effects of different parity of high-yield and low-yield dairy cows on milk yield,milk composition and lactation persistence,so as to provide reference for raising management pattern optimization and increasing life of dairy cows dairy cows.【Method】12406 dairy cows from 17 dairy farms in Beijing and Hebei Province,China were grouped according to the criterium of high yielding(48.69±6.88 kg/d)and low yielding(23.47±5.28 kg/d).Raw data based on the DHI(Dairy Herd Improvement)report was pretreated to obtain 5158 high-yield dairy cows and3110 low-yield dairy cows. One-way ANOVA was used for homogeneity of variance test and multivariate correlation analysis was conducted by Pearson two-sided test. The differences between groups were analyzed by LDS and Duncan's multiple comparison,and the correlation between the 2 variables was analyzed according to Spearson correlation coefficient.【Result】Parity influenced milk yield,milk composition and lactation persistence:the daily milk yields of the third and fourth parity of high yielding dairy cows were significantly higher than those of other fetuses(P<0.05,the same below)and somatic cell count(SCC)of high-yield dairy cows after the fourth parity was significantly higher than that of other parity;daily milk yield and milk lactose rate of the first parity of low-yield dairy cows were significantly higher than those of other parities,and the SCC was significantly lower than that of other parities. In terms of lactation persistence,the first parity of high-yield dairy cows performed better than the third,fourth and the fifth parity,the first parity of low-yield dairy cows performed better than the other parities and no significant difference was found in other parities(P>0.05,the same below). Lactation persistence of high-and low-yield dairy cows was not significantly correlated with SCC but was significantly correlated with milk yield. Correlations of milk yield,milk component and SCC were consistent except for correlation between dry matter content and milk yield and correlation between milk fat rate and lactose rate. Extremely significant positive correlation was found between daily milk yield and milk lactose rate(P<0.01,the same below)and extremely significant negative correlation was found between daily milk yield and SCC. Composition and persistence between high-yielding and low-yielding dairy cows,and there was a significant positive correlation between daily milk yield and corrected milk and lactose rate. SCC was significantly positively correlated with milk fat rate and milk protein rate.【Conclusion】The third and the fourth parities of high-yield dairy cows performed the best and the first to the third parities of low-yield dairy perform the best. Parity of high-and low-yield cows influences milk yield,milk composition and lactation persistence. But the trend of milk yield and milk composition under different parities is difference. Therefore,with improved basic feeding management,nutrition supply should be optimized,feed formula should be timely adjusted and classification and grouping of dairy cows should be done appropriately to better utilize the optimal parity of dairy cows and increase the economic benefits.