Management of heat stress in lambs

Heat stress impairs lamb growth, meat and milk quality, reproductive performance, and immune function. Elevated temperatures increase respiratory rate and rectal temperature, leading to hyperthermia when heat loss is insufficient. Rectal temperature rises above normal above 32 °C, with panting occurring at 40 °C under low humidity. Dietary changes affect digestibility, rumen pH, microbial populations (e.g., Clostridium cocoides, Streptococcus, Fibrobacter), volatile fatty acids, and methane production. Rumen function is altered, increasing acidosis risk. Key mitigation strategies include free water access, shade, cooling systems, high-protein (≥23%) and high-fat (≥30%) diets, and veterinary consultation.