Physiological impact of amino acids during heat stress in ruminants

The loss in value due to reductions in milk and meat production from heat stress (HS) worldwide by the end of the century have recently been estimated at $14.9 to $39.9 billion per year (Thornton et al., 2021). These losses are predicted to be mostsevere in tropical regions where an increase in beef production, for example, to feed the growing population worldwide is expected by 2050 (Cooke et al., 2020). Common HS abatement practices including increasing shaded areas, increasing air velocity by use of fans, and the use of water-soaker lines to increase evaporative heat loss have been implemented on farms. Despite this, the continued increase in environmental temperature and the duration and frequency of droughts will impact not only animal numbers, but also productive ef!ciency worldwide and the economic return (Wankar et al., 2021). Although tackling the negative impact of global warming on productive efficiency and wellbeing requires multiple management approaches, greater knowledge of physiological mechanisms that are altered by HS will be valuable. This is particularly true in parts of the world where intensive production systems are characterized by animals of high-genetic merit that not only has resulted in marked increases in milk or beef production, but also in the amount of heat (i.e., heat increment) produced per unit of feed consumed (West, 2003; Cooke et al., 2020). Escalating global temperatures combined with global demand for livestock products has resulted in HS becoming an important ongoing challenge facing the global livestock industry.