Eslamizad Mehdi, Lamp Ole, Derno Michael, Kuhla Björn
Institute of Nutritional Physiology 'Oskar Kellner', Leibniz Institute for Farm Animal Biology (FBN), Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany; Department of Animal Science, Campus of Agriculture and Natural Resources, P.O. Box 4111, University of Tehran, Karaj, Iran.
Institute of Nutritional Physiology 'Oskar Kellner', Leibniz Institute for Farm Animal Biology (FBN), Wilhelm-Stahl-Allee 2, 18196 Dummerstorf, Germany.
Physiol Behav. 2015 Jun 1;145:64-70. doi: 10.1016/j.physbeh.2015.03.044. Epub 2015 Mar 31.
The objective of the present study was to integrate the dynamics of feed intake and metabolic oxidation in late pregnant and early lactating Holstein cows under heat stress conditions. On day 21 before parturition and again on day 20 after parturition, seven Holstein cows were kept for 7days at thermoneutral (TN) conditions (15°C; temperature-humidity-index (THI)=60) followed by a 7day heat stress (HS) period at 28°C (THI=76). On the last day of each temperature condition, gas exchange, feed intake and water intake were recorded every 6min in a respiration chamber. Pre- and post-partum cows responded to HS by decreasing feed intake. The reduction in feed intake in pre-partum cows was achieved through decreased meal size, meal duration, eating rate and daily eating time with no change in meal frequency, while post-partum cows kept under HS conditions showed variable responses in feeding behavior. In both pre- and post-partum cows exposed to heat stress, daily and resting metabolic heat production decreased while the periprandial respiratory quotient (RQ) increased. The prolonged time between meal and the postprandial minimum in fat oxidation and the postprandial RQ maximum, respectively, revealed that HS as compared to TN early-lactating cows have slower postprandial fat oxidation, longer feed digestion, and thereby showing a shift from fat to glucose utilization.
本研究的目的是综合热应激条件下妊娠后期和泌乳早期荷斯坦奶牛的采食量和代谢氧化动态变化。在分娩前21天以及分娩后20天，7头荷斯坦奶牛先在热中性（TN）条件下（15°C；温湿度指数（THI）=60）饲养7天，随后在28°C（THI=76）的条件下经历7天的热应激（HS）期。在每个温度条件的最后一天，在呼吸室内每6分钟记录一次气体交换、采食量和饮水量。产前和产后奶牛对热应激的反应是采食量下降。产前奶牛采食量的减少是通过减小采食餐量、缩短采食餐时、降低采食速率和减少每日采食时间实现的，采食频率没有变化，而处于热应激条件下的产后奶牛采食行为表现出不同的反应。在暴露于热应激的产前和产后奶牛中，每日和静息代谢产热均下降，而围餐期呼吸商（RQ）升高。采食餐与餐后脂肪氧化最小值以及餐后呼吸商最大值之间的时间延长，分别表明与热中性条件下的奶牛相比，热应激条件下的泌乳早期奶牛餐后脂肪氧化较慢、饲料消化时间较长，从而显示出从脂肪利用向葡萄糖利用的转变。
