Heat stress on calves and heifers: a review  

作　　者：Jingjun Wang Jinghui Li Fengxia Wang Jianxin Xiao Yajing Wang Hongjian Yang Shengli Li Zhijun Cao 

机构地区：[1]State Key Laboratory of Animal Nutrition,Beijing Engineering Technology Research Center of Raw Milk Quality and Safety Control,College of Animal Science and Technology,China Agricultural University,Beijing 100193,PR China [2]Department of Animal Science,University of California,Davis,California 95616,USA [3]Beijing CNAgri Animal Science Technology Research Center,Beijing 100193,PR China.

出　　处：《Journal of Animal Science and Biotechnology》2020年第4期929-936,共8页畜牧与生物技术杂志（英文版）

基　　金：funded by National Key Research and Development Program of China (2018YFD0501600);Key Research and Development Project of Hebei (19226625D)。

摘　　要：The current review is designed with aims to highlight the impact of heat stress(HS) on calves and heifers and to suggest methods for HS alleviation. HS occurs in animals when heat gain from environment and metabolism surpasses heat loss by radiation, convection, evaporation and conduction. Although calves and heifers are comparatively heat resistant due to less production of metabolic heat and more heat dissipation efficiency, they still suffer from HS to some degree. Dry matter intake and growth performance of calves and heifers are reduced during HS because of redistributing energy to heat regulation through a series of physiological and metabolic responses, such as elevated blood insulin and protein catabolism. Enhanced respiration rate and panting during HS accelerate the loss of CO2, resulting in altered blood acid-base chemistry and respiratory alkalosis. HS-induced alteration in rumen motility and microbiota affects the feed digestibility and rumen fermentation. Decreased luteinizing hormone, estradiol and gonadotrophins due to HS disturb the normal estrus cyclicity, depress follicular development, hence the drop in conception rate. Prenatal HS not only suppresses the embryonic development by the impaired placenta, which results in hypoxia and malnutrition, but also retards the growth, immunity and future milk production of newborn calves. Based on the above challenges, we attempted to describe the possible impacts of HS on growth, health, digestibility and reproduction of calves and heifers. Likewise, we also proposed three primary strategies for ameliorating HS consequences. Genetic development and reproductive measures, such as gene selection and embryo transfers, are more likely long-term approaches to enhance heat tolerance. While physical modification of the environment, such as shades and sprinkle systems, is the most common and easily implemented measure to alleviate HS. Additionally, nutritional management is another key approach which could help calves and heifers maintain homeostasis and prevent

关 键 词：CALF Energy Heat stress HEIFER REPRODUCTION 

分 类 号：S823[农业科学—畜牧学]