热应激对不同泌乳阶段奶牛日产奶量的影响

Effects of Heat Stress on Daily Milk Production of Dairy Cows in Different Lactation Periods

对热应激条件下湖北省黄冈市某规模化奶牛场不同泌乳阶段奶牛日产奶量的变化进行了调查研究。结果表明,处于非热应激期和热应激恢复期的泌乳早期奶牛的日产奶量极显著(P<0.01)高于处于中度热应激期的泌乳早期奶牛的日产奶量,处于非热应激期的泌乳中期奶牛的日产奶量显著(P<0.05)高于处于中度热应激期的泌乳中期奶牛的日产奶量。中度热应激期与非热应激期相比,温湿指数(THI)每增加1个单位,泌乳早期、泌乳中期和泌乳后期的奶牛日产奶量分别下降0.46、0.37和0.30 kg/头;热应激恢复期与中度热应激期相比,THI每降低1个单位,泌乳早期、泌乳中期和泌乳后期的奶牛日产奶量分别增加0.45、0.16和0.05 kg/头。因此,泌乳早期的奶牛受到热应激的影响程度大于泌乳中期的奶牛,泌乳后期的奶牛受到热应激的影响程度最小。建议奶牛场合理安排奶牛的配种与产犊时间,在上一年的10、11、12月尽量不给奶牛配种,避开母牛在7、8、9月产犊,从而避免热应激对奶牛泌乳早期和中期的影响。

The effects of heat stress on the daily milk yield of dairy cows in different lactations were investigated in a largescale dairy farm at Huanggang city.The results showed that the mean daily milk production of early lactation cows in nonheat stress period and heat stress recovery period were significantly higher than those in moderate heat stress period（P〈0.01）.The mean daily milk production of middle lactation cows in non-heat stress period was significantly higher than those in moderate heat stress period（P0.05）.Compared with the non-heat stress period,the mean daily milk production of early,middle and late lactation cows in moderate heat stress period decreased by 0.46,0.37 and 0.30 kg cattle,respectively,when the temperature-humidity index（THI） increased by one unit.The mean daily milk production of early,middle and late lactation cows in heat stress recovery period were higher than those in moderate heat stress period by 0.45,0.16 and 0.05 kg cattle,respectively,when THI decreased by one unit.It is indicated that the degree of heat stress affecting early lactation cows was greater than middle and late lactation cows.It is recommended that the mating and calving time of cows should be reasonable arranged.Mating in October,November and December,and calving in July,August and September should be avoided to avoid the early and middle lactation of them under heat stress period.