A scoping review and systematic map of primary studies assessing heat stress on reproductive, physiological, and productive parameters of farm animals (original) (raw)
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Heat stress effects on livestock: molecular, cellular and metabolic aspects, a review
Journal of Animal Physiology and Animal Nutrition, 2015
Elevated ambient temperatures affect animal production and welfare. Animal's reduced production performances during heat stress were traditionally thought to result from the decreased feed intake. However, it has recently been shown that heat stress disturbs the steady state concentrations of free radicals, resulting in both cellular and mitochondrial oxidative damage. Indeed, heat stress reorganizes the use of the body resources including fat, protein and energy. Heat stress reduces the metabolic rates and alters post-absorptive metabolism, regardless of the decreased feed intake. Consequently, growth, production, reproduction and health are not priorities any more in the metabolism of heat-stressed animals. The drastic effects of heat stress depend on its duration and severity. This review clearly describes about biochemical, cellular and metabolic changes that occur during thermal stress in farm animals.
Impact of heat stress on the reproduction of farm animals and strategies to ameliorate it
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Animals are susceptible to heat stress under tropical environmental conditions. Exposure of growing male and female animals to severe heat stress during summer adversely affects their growth and reproductive traits, reduces the resistance to diseases and induces infertility in farm animals and represents a major source of economic loss to the livestock sector. During the summer season, animals usually suffer from summer sterility due to prevailing hot and humid conditions. In female animal's age at puberty, estrous signs, ovulation time, ova quality, conception rate, embryonic development, embryo size, embryo weight and hormonal balance are affected by exposure to heat stress. The most sensitive to heat stress are growing ovarian follicles. Heat stressinduced changes in growing follicles can be expressed later as compromised maturation and developmental capacity of the ovulating oocyte. In males, sex hormone levels, spermatogenesis, temporary sterility, libido, ejaculate volume, macroscopic as well as microscopic semen characteristics in an ejaculate are affected, and sperm abnormalities and dead sperm increase by exposure to the heat stress. Various heat stress amelioration technologies have evolved to circumvent the fertility reduction in dairy cattle and other livestock animals. New breakthroughs such as estrus synchronization, embryo transfer technique, cryopreservation of gametes and genetic manipulation, nutraceuticals (feed additives, pre and probiotics) and managerial changes may exist to improve summer fertility. This review summarizes the most up-to-date information on the effects of heat stress on the male and female reproduction especially under tropical conditions.
Symptoms of Heat Stress in Tropical and Subtropical Regions on Farm Animals
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The thermal relief regions for maximum animals are ranged 4 °C and 25 °C. In tropical and subtropical countries ambient temperature surpasses 25° C and animals undergo high environmental temperatures. Most physiological and biochemical variations in animals could take place to care for essential cell functions in contradiction of stressful conditions and to certification a fast retrieval from modest hypothermic destruction. Animal performance is reduced due to extreme variations in biological purposes affected by heat-stress conditions.
Journal of Animal Behaviour and Biometeorology, 2017
This review aimed to detail the main information pertinent to the physiological and behavioral mechanisms evidenced in cattle under heat stress conditions. Brazilian cattle-breeding represents the second largest herd in the world, promoting great impact on the country's exports. Throughout their adaptability, these animals were submitted to different environments, which directly influence productive and reproductive performance, seeking compensatory mechanisms to maintain body homeostasis. Therefore, we can consider that heat stress directly affects the physiological and behavioral responses of cattle subjected to high temperatures. Adaptability of breeds to tropics should be considered of extreme importance in the choice of a productive activity for cattle-breeding and, particularly, in hot environments.
Physiological consequences of heat stress in pigs
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Heat stress negatively influences the global pork industry and undermines genetic, nutritional, management and pharmaceutical advances in management, feed and reproductive efficiency. Specifically, heat stress-induced economic losses result from poor sow performance, reduced and inconsistent growth, decreased carcass quality, mortality, morbidity, and processing issues caused by less rigid adipose tissue (also known as flimsy fat). When environmental conditions exceed the pig’s thermal neutral zone, nutrients are diverted from product synthesis (meat, fetus, milk) to body temperature maintenance thereby compromising efficiency. Unfortunately, genetic selection for both increased litter size and leaner phenotypes decreases pigs’ tolerance to heat, as enhanced fetal development and protein accretion results in increased basal heat production. Additionally, research has demonstrated that in utero heat stress negatively and permanently alters post-natal body temperature and body composi...
Heat stress in swine: Impact and strategies to combat
2021
Our climate is regularly changing. Since industrial revolution, global temperature has increased to 1.5°C. Numerous health and environmental challenges troublesome the swine industry worldwide. Heat stress (HS) during summer is one seasonal condition that has an immensely negative effect on pig farmers which may let stifle their profitability if proper management strategies are not adopted in time. Heat stress (HS) is being one of the largest impediments to efficient animal agriculture which causes changes in behavior, physiology, and metabolism of animals. It causes serious health impacts that result in diminished performance, especially in breeding herds and finisher pigs, eventually, economic losses for the farmer.
In utero heat stress increases postnatal core body temperature in pigs1,2
Journal of Animal Science, 2015
Although advances in technology (i.e., cooling systems and management practices) have partially ameliorated the negative effects of heat stress (HS), growth performance continues to be reduced while morbidity and mortality are increased in almost all agriculturally important species during the warm summer months (Collin et al., 2001; Brown-Brandl et al., 2004; Baumgard and Rhoads, 2013). Further, genetic selection for traditional production traits (i.e., enhanced lean tissue accretion) compromises HS tolerance as synthesizing and maintaining muscle generates increased metabolic heat (Brown-Brandl et al., 2001). Consequently, HS is one of the primary factors limiting profitable animal protein production, and if the frequency of severe hot weather increases as predicted (McGeehin and Mirabelli, 2001), the sustainability of some animal industries may be regionally threatened. Although primarily an economic concern in most countries, HS and future climate change are food security and humanitarian issues in some developing nations (Baumgard and Rhoads, 2013). Although in utero HS (iuHS) negatively impacts fetal development and can be teratogenic (Graham et in utero heat stress increases postnatal core body temperature in pigs 1,2
Mitigation of the Heat Stress Impact in Livestock Reproduction
Theriogenology, 2017
Heat stress affects the fertility and reproductive livestock performance by compromising the physiology reproductive tract, through hormonal imbalance, decreased oocyte quality and poor semen quality, and decreased embryo development and survival. Heat stress decreases the secretion of luteinizing hormone and estradiol resulting in reduced length and intensity of estrus expression, increased incidence of anoestrus and silent heat in farm animals. Oocytes exposed to thermal stress lose its competence for fertilization and development into the blastocyst stage, which results in decreased fertility because of the production of poor quality oocytes and embryos. Furthermore, low progesterone secretion limits the endometrial functions, and subsequently embryo development. In addition, the increased secretion of endometrial prostaglandin F2 alpha during heat stress threatens the maintenance of pregnancy. In general, the percentage of conception rate was found to be reduced by 4.6% for each unit increase in temperature humidity index (THI) above 70, and heat stress during pregnancy further slows down the growth of the foetus and results in lower birth weight. In tropical and subtropical regions, during hot days, the testicular temperature may increase and impair both the spermatogenic cycle and semen quality, which culminates in decreased bull fertility. The effects of heat stress on livestock can be minimized via adapting suitable scientific strategies comprising physical modifications of the environment, nutritional management and genetic development of breeds that are less sensitive to heat stress. In addition, the summer infertility may be countered through advanced reproductive technologies involving hormonal treatments, timed artificial insemination and embryo transfer, which may enhance the chances for establishing pregnancy in farm animals.
Heat stress of cattle from embryonic phase until culling
Acta Agraria Debreceniensis
Heat stress becomes a serious problem in the livestock sector as it affects cows' performance negatively. The objective of this paper review is to investigate the effects of heat stress during the different phases of the life cycle of cows; embryos, calves, heifers, and cows. Heat stress during early maternal gestation affects the ability of embryos to develop increasing the risk of abortion and early embryonic death. Heat stress during late maternal gestation affects the performance of calves and heifers later in their life, as it reduces growth performance, conducts physiological changes, impaired immunity, changes the behavior, and reduces the length and intensity of the estrus in heifers with decreasing in milk production in the first lactation. On the level of cows, milk quality and production, meat quality, and the final body weight decrease under hot temperatures. Heat stress decreases the conception rate, alters follicle growth, and estrous symptoms. Hormones secretion a...