Faecal glucocorticoid metabolites and body temperature in Australian merino ewes (Ovis aries) during summer artificial insemination (AI) program

Abstract

Reproductive wastage is a key issue for sheep producers, both regionally and globally. The reproductive output of farm animals can be influenced by physiological and environmental factors. Rapid and reliable quantification of physiological stress can provide a useful tool for designing and testing on-farm management interventions to improve farm animal welfare and productivity. In this study, we quantified physiological stress non-invasively using faecal glucocorticoid metabolites-FGMs analysis and body temperature measurements of 15 superovulated donor merino ewes (Ovis aries) during participation in artificial insemination (AI) program conducted during 2015/2016 Australian summer. We hypothesized that low percentage transferable embryos in donor merino ewes will be associated positively with higher body temperature and/or higher FGMs in these ewes. Temperature humidity index (THI) was calculated and found within high thermal stress range during the two AI trials. Overall, results showed none of the factors (ewe ID, AI trial no., THI or FGMs) were significant for reduced percentage transferrable embryos, except ewe body temperature was highly significant (p = 0.014). Within AI trial comparisons showed significant positive associations between higher FGMs and body temperature with reduced transferrable embryos. These results suggest that Australian merino ewes participating in summer AI trials can experience physiological stress. Prolonged activation of the stress endocrine response and high body temperature (e.g. ensued from heat stress) could impact on ewe reproductive output. Therefore, future research should apply minimally invasive physiological tools to gather baseline information on physiological stress in merino sheep to enable the development of new farm-friendly methods of managing stress.

A Review on the Influence of Climate Change on Sheep Reproduction

“…Previous research into fertility and reproductive ability in mammals also demonstrated, through a wide variety of trials and scientific reviews, the physiological responses associated with the perception or recognition of internal or external stressors [9,10]. Most recently, Narayan et al [11] determined that summer heat wave can impact the management outcomes of commercial livestock reproduction programs involved in artificial insemination (AI) and embryo transfer (ET) through the generation of physiological stress and early loss of embryos in 'hot ewes' [11]. New research into how climatic induced heat stress represents a physiological challenge to normal expression of life-history traits such as growth, development, behaviour and reproduction in domesticated farm animals is gaining interest throughout the agricultural sector worldwide.…”

“…A Review on the influence of Climate Change on sheep reproduction DOI: http://dx.doi.org /10.5772/intechopen.86799 In sheep, Narayan et al [11] showed that heat stress reduces embryo production during AI/ET because the physiological and cellular aspects of reproductive function and early embryo development are disrupted. Thus, climatic change induced heat stress can diminish reproductive capacity in the Merino ewe due to an increase in body temperature as it is exposed to elevated ambient temperature, and by the physiological adaptations of cells coping with thermal stress [35,36].…”

“…Within these challenges driven by the climatic change, sheep producers should anticipate changes in preimplantation environmental conditions (1), the uterine and placental competency (2), and adequate nutrient transport across the placenta (3), all of which are stressors that can all alter foetal development trajectories [50]. Alliston and Ulberg [54], Sawyer [7] and recently Narayan et al [11] provided concise evidence that ewes subject to high air temperature at time of mating will have a reduced reproductive rate through embryo loss [8,11,54]. Thermal stress is also known to influence the superovulation response in sheep [55] and cattle [56,57] in a multiple ovulation and embryo transfer program (MOET) [58].…”

“…Oocyte and/or embryo quality is most affected when ewes are exposed to a hot environment during the first 3 days after artificial insemination [8]. High internal body temperature > 39.5°C leads to high cortisol (stress) levels and subsequently reduced levels of transferable eggs in AI/ET [11].…”

Physiological implications, cellular responses and lactational performance of Saanen goats under heat stress

“…Farm ruminants are constantly exposed to environmental factors and climate challenges that could cause stress and negatively impact their production and reproduction (MINTON, 1994;McMICHAEL et al, 2007;NARAYAN;PARISELLA, 2017;NARAYAN et al, 2018). In tropical latitudes, ruminants are maintained on grassland pasture and are exposed, most of the time, to intense solar radiation.…”