Responses of dairy cows to short-term heat stress in controlled-climate chambers
Responses of dairy cows to short-term heat stress in controlled-climate chambers
复制标题
DOI：
10.1071/an16472
复制
发表时间：
2017-06-01
影响因子：
1.4
通讯作者：
Hayes, B. J.
中科院分区：
文献类型：
--
作者：
Garner, J. B.;Douglas, M.;Hayes, B. J.
本研究的目的是描述泌乳奶牛的生理和生产反应期间和之后突然暴露于温带气候热浪条件下，与奶牛在热中性条件下相比。将12头泌乳经产Holstein-Friesian奶牛在气候控制室中饲养4天。6头奶牛暴露于短期温度和湿度挑战（THc，诱导中度热应激的昼夜温度和湿度波动;温度湿度指数74-84），6头奶牛暴露于热中性条件（THn，温度湿度指数55-61）。还在7天实验前和14天实验后期间测量了奶牛。测定了热应激的生理指标，包括直肠和阴道温度以及呼吸速率，这表明在受控气候室中的THc引起中度热应激。与THn治疗组相比，暴露于4天THc的奶牛的产奶量减少了53%，干物质摄入量减少了48%。THc奶牛的产奶量在第7天恢复到实验前的产奶量，在实验后第4天恢复到干物质摄入量。短期热挑战通过动员脂肪组织（如增加的非酯化脂肪酸所示）和骨骼肌中的氨基酸（如增加的尿素氮所示）诱导代谢适应，以补偿营养摄入量减少和能量消耗增加。内分泌反应包括更高的催乳素浓度，这与体温调节和水代谢有关。暴露于THc的奶牛表现出生产和身体反应，促进了较低的代谢产热和更大的散热，试图在短期热暴露期间保持体内平衡。这些结果表明，在受控气候室中对奶牛施加的条件足以诱导热应激反应，并对泌乳奶牛的生产产生不利影响，并且在热挑战后恢复正常摄食量和产奶量之间的延迟表明正在发生一段时间的代谢恢复。
The objective of the present research was to describe the physiological and production responses of lactating dairy cows during and after sudden exposure to temperate-climate heat-wave conditions, compared with cows in thermoneutral conditions. Twelve lactating multiparous Holstein-Friesian dairy cows were housed in controlled-climate chambers for 4 days. Six were exposed to a short-term temperature and humidity challenge (THc, diurnal temperature and humidity fluctuations inducing moderate heat stress; temperature humidity index 74-84) and six cows were exposed to thermoneutral conditions (THn, temperatur humidity index 55-61). Cows were also measured during a 7-day pre-experimental and 14-day post-experimental period. Physiological indicators of heat stress were measured, including rectal and vaginal temperature and respiration rate, which indicated that the THc in controlled-climate chambers induced moderate heat stress. The cows exposed to the 4-day THc reduced their milk yield by 53% and their dry-matter intake by 48%, compared with the cows in the THn treatment. Milk yield of THc cows returned to pre-experimental milk yield by Day 7 and dry-matter intake by Day 4 of the post-experimental period. The short-term heat challenge induced metabolic adaptations by mobilising adipose tissue, as indicated by increased non-esterified fatty acids, and amino acids from skeletal muscle, as indicated by increased urea nitrogen to compensate for reduced nutrient intake and increased energy expenditure. Endocrine responses included greater prolactin concentrations, which is associated with thermoregulation and water metabolism. The cows exposed to THc displayed production and physical responses that facilitated lower metabolic heat production and greater heat dissipation in an attempt to maintain homeostasis during the short-term heat exposure. These results indicated that the conditions imposed on the cows in the controlled-climate chambers were sufficient to induce heat-stress responses and adversely affected production in the lactating dairy cow, and the delay between the return to normal feed intake and milk yield following the heat challenge suggests a period of metabolic recovery was occurring.