全球变化知识资源中心

Heat and water stress are rampant challenges in animal production as a result of climate change. Sixteen lactating goats of the Alpine and Saanen breeds were subjected to water restriction for 16 h on two consecutive days followed by rehydration, along with naturally rising temperature that culminated by the end of an experimental period of one week. Data were collected from the animals on four separate days representing their status under control conditions when temperature was still within their comfort zone, on the second day of the water restriction treatment, 24 h after rehydration and finally on the day when ambient temperature was above the normal average. Animals showed an increase in rectal temperature with time as ambient temperature increased. The heat stress was reflected by the decrease in pCO(2) and HCO3 concentrations consistent with the onset of panting, while milk production was maintained but the concentration of major milk components decreased. Water stress, on the other hand, led to hemoconcentration with increased osmolality, Na+, urea, glucose and albumin concentrations and an increase in milk lactose. The changes in blood parameters were reversed 24 h after rehydration but were slightly lower than normal, indicating the need for more than 24 h to re-adjust water balance in these lactating animals. Finally, the latency between first feeding and the following drinking event after return from milking showed that the shortest latency was under the water restriction treatment indicating thirst, in addition, a trend for shorter latency before drinking over the experimental period was observed in response to the rise in temperature. This experiment showed the capacity of these highly productive breeds to withstand mild water and heat stress. However, subtle changes in physiology and milk composition warrant further research into their effect on milk quality and animal welfare.