北京地区夏季体温变化对奶牛泌乳性能的影响分析

Analysis on the effect of change in body temperature on lactation performance of dairy cows in summer in Beijing area

为了探究夏季热应激状态下奶牛体温变化对产奶量和乳成分的影响,试验测定北京地区5个牛场1 691头中国荷斯坦泌乳母牛连续2 d上午和下午的直肠温度(RT)、体况评分(BCS)以及当月泌乳性能(DHI数据),在固定模型中考虑了测定年、场(年场效应)、胎次和泌乳阶段三个分类效应,且将下午直肠温度(RT_2)、上午下午直肠温度差(△RT)和BCS作为回归协变量。结果表明:校正奶量和日奶量对RT_2回归均极显著(P<0.01);△RT_2对日奶量有显著(P<0.05)的影响,对校正奶量有极显著(P<0.01)的影响;RT_2、△RT对乳脂率、乳蛋白率和脂蛋比均有显著(P<0.05)或极显著(P<0.01)影响,乳脂率和脂蛋比随着RT_2的升高而增大,随着△RT的增大而减小;而乳蛋白率随着RT_2的升高而减小,随着△RT的增大而增大。说明直肠温度作为奶牛热应激反应较好的量化指标,同时与奶牛泌乳性能有密切关系,可以将其作为管理指标,密切监测提高管理效率。

To explore the effect of change in body temperature of dairy cows on milk yield and milk components under the heat stress during summer,the rectal temperature( RT) for two days in the morning and afternoon,body condition score( BCS) and monthly lactation performance based on DHI data were measured in 1 691 Chinese Holstein lactating cows from 5 dairy farms in Beijing area. Three categorical factors including year and farm data collected( year- farm effect),parity,and lactation stages were considered in the fixed model,and the rectal temperature in the afternoon( RT_2),rectal temperature difference between the morning and afternoon( △RT),and BCS were used as regression covariates. The results showed that the corrected milk yield and daily milk yield on RT_2 regression were highly significant( P < 0. 01),and the square of △RT_2had a significant effect( P < 0. 05) or highly sigrificant effect( P < 0. 01) on the daily milk yield or the corrected milk yield,respectively; both RT_2 and △RT had significant( P < 0. 05) or highly significant( P < 0. 01) effects on the milk fat percentage,milk protein percentage and fat- to- protein ratio; the milk fat percentage and fat- to- protein ratio increased with the increase of RT_2,but decreased with the increase of △RT; while the milk protein percentage decreased with the increase of RT_2,but increased with the increase of △RT. The results indicate that rectal temperature as a good quantitative indicator for heat stress response in dairy cows,can be used as a management index to improve the management efficiency through frequent monitoring due to its close relationship with lactation performance of dairy cows.