National Institute of Animal Science, RDA, Suweon, South Korea.
Anim Sci J. 2010 Feb;81(1):58-62. doi: 10.1111/j.1740-0929.2009.00711.x.
Three late-lactation Holstein cows were used to determine the effects of environmental temperature on performance and energy partitioning. Each cow was housed in a respiratory chamber for 30 consecutive days and exposed to three different conditions of environmental temperature: (i) 20 degrees C and 20 degrees C (20 degrees C), (ii) 25 degrees C and 20 degrees C (25 degrees C), (iii) 30 degrees C and 25 degrees C (30 degrees C) during the day and night, respectively. The temperature was switched in an interval of 10 days. Humidity in the chamber was maintained at 55-65% through the entire experimental period. The daily mean as well as morning and evening rectal temperatures of Holstein cows increased linearly (P < 0.05) as chamber temperature increased. There was a significant linear reduction in dry matter (DM) intake (P < 0.05) and an increase in DM digestibility (P < 0.05). The response in milk yield, however, was not affected by heat stress. There were no significant differences among treatments for intake energy, heat production, net energy for lactation and net energy for gain. This results of this study disagreed with the assumption that late lactation cows gave priority to increasing body tissue at the expense of milk production under thermal stress.
本研究选用三头泌乳后期荷斯坦奶牛，研究环境温度对奶牛生产性能和能量分配的影响。每头奶牛在呼吸室中饲养 30 天，分别暴露在三种不同的环境温度条件下：（i）20°C 和 20°C（20°C），（ii）25°C 和 20°C（25°C），（iii）白天和夜间的温度分别为 30°C 和 25°C（30°C）。温度以 10 天为间隔进行切换。整个实验期间，室内湿度保持在 55-65%。荷斯坦奶牛的每日平均、清晨和傍晚直肠温度随室内温度的升高呈线性增加（P < 0.05）。干物质（DM）摄入量呈显著线性下降（P < 0.05），DM 消化率呈线性上升（P < 0.05）。然而，热应激对产奶量没有影响。在能量摄入、产热量、泌乳净能和增重净能方面，各处理组之间没有显著差异。本研究结果与假设不符，即在热应激下，泌乳后期奶牛优先增加体组织而不是产奶。
