Impact of Climate Change on Sheep Reproduction

Abstract

The climate is changing faster than the predictions, with expectations of more frequent warm spells, heat waves and heavy rainfall in the future. The magnitude of these will depend on the geographical features of that region. The extreme environmental conditions due to change in climate will impose various stresses on sheep and consequently will adversely affect their reproductive performance. Animals will experience heat stress due to high temperature and more solar radiation, and nutritional stress due to reduced quantity and quality of feed because of low rainfall, more droughts, poor crop yields and less pasture growth. Reproduction is a complex process that involves a timed sequence of physiological and psychological events governed by hormones, metabolites and environmental signals. In both the sexes, these events are very sensitive to high temperature and under-nutrition. Nearly all the reproductive processes such as gametogenesis, puberty, gamete transport, fertilization, early embryonic development, maternal recognition of pregnancy, gestation, parturition and post-partum recovery are influenced by environmental stresses either directly by affecting the functions of reproductive organs or by blocking the hormone-mediated cellular functions of the hypothalamic-pituitary-gonadal (HPG) axis. Sheep husbandry is the main activity of livelihood security of large populations in hot arid and semi-arid climates and is based on grazing. Sheep often have to walk long distances under hot solar radiation and they experience deprivation of feed for short or long periods. The potential effects of climate change on sheep reproduction would be increased incidence of reproductive disorders such as delayed puberty, fertilization failure, embryo mortality, retardation of foetal development and growth, abortion, and premature or still birth, culminating in low reproductive efficiency of animals. Further, climate change may affect seasonal breeding in sheep due to mismatch of nutrient availability with commencement of reproductive activities.