Mitigation of the Heat Stress Impact in Livestock Reproduction

Abstract

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.

Effects of fossil shell flour supplementation on heat tolerance of dohne merino rams

“…It was found that the decrease in ST as the FSF inclusion levels increased in Dohne Merino rams were the direct effect of FSF during the experiment. The result from this study aligned with the report of ( Krishman et al., 2017 ) that observed that, dietary supplementation of trace elements to animal feeds can ameliorate adverse effect of heat stress. Since, FSF is abundantly rich in about 14 trace elements, the addition of FSF to Dohne Merino rams’ diet can be concluded to reduced ST in FSF supplemented diet compared to FSF non-supplemented diet.…”

Will dairy cattle production in West Africa be challenged by heat stress in the future?

“…& The future climate scenario analyses indicate that the length of consecutive days of heat stress for dairy cattle with THI higher than the severe/danger threshold is likely to increase in future periods in WA. These changes are also important because the severity of heat stress impact on milk production would increase by increasing the length of heat stress period (Rojas-Downing et al 2017;Krishnan et al 2017). & Based on GFDL-ESM2M, HadGEM2-ES, and MPI-ESM-MR projections under the RCP4.5 scenario, by 2071-2100, around 2.0, 5.8, and 9.8% of dairy cattle population in WA would experience dangerous heat stress events 40% (~145 days) more frequent than the historical period, respectively.…”

Association of IGFBP-3 gene polymorphism g. 3.930 G>A with birth size and birth weight in crossbred beef cattle

“…The average BW of Brahman Cross cattle was 35 kg (Holmes et al, 1992), Zebu-Wagyu crosses were 28 kg (Hearnshaw et al, 2001), and Zebu-Belgian Blue crosses were 35 kg (Nogueira et al, 2016). Average cattle BW in this study tends to be smaller due to environmental factors, high temperatures as in tropical environments will reduce birth weight compared to temperate environments (Krishnan et al, 2017).…”