Abstract: The aim of this study was to explore the effects of parity and lactation stage on somatic cell counts in dairy herd improvement (DHI) milk samples and milk production loss in dairy cows. The results indicated that the somatic cell score (SCS) was increased with parity, and SCSs at different stages of lactation performance in different parities were different. SCS was increased with lactation time in first-parity dairy cows and SCS values were significantly different at three lactation stages (P < 0.05). The same trend was observed for SCS in second- and third-parity cows; SCS was higher at the early lactation stage than at the middle lactation stage, and its values at the two stages were significantly lower than that at the late lactation stage (P < 0.05). Milk production loss in dairy cows generally rose with parity and was higher at the early and late stages of lactation than at the middle stage.

Key words: dairy cow; parity; lactation stage; somatic cell score (SCS); milk production loss

摘要： 通过奶牛生产性能（dairy herd improvement，DHI）测定体细胞数，探究奶牛的胎次及其不同泌乳阶段对其乳体细胞数（somatic cell count，SCC）和乳损失量的影响。通过对某养殖场泌乳期奶牛DHI的测定进行分析，结果表明：体细胞评分（somatic cell score，SCS）随奶牛胎次的增加而增加，但SCS在不同胎次的不同泌乳阶段表现有所不同。一胎牛SCS随着泌乳期的延长而增加，前期、中期与后期的SCS呈显著性差异（P＜0.05）；二胎牛与三胎牛SCS呈现相同变化规律，泌乳前期的SCS较泌乳中期高，而泌乳后期SCS显著高于前2个泌乳阶段（P＜0.05）。乳损失量随胎次的增加整体呈现增加趋势，且泌乳早期和泌乳后期乳损失量高于泌乳中期。

关键词: 奶牛；胎次；泌乳阶段；体细胞评分；乳损失量