The relationship between air temperature, scrotal surface area and testis temperature in rams

Abstract

Scrotal surface area, intra-testicular, and subcutaneous scrotal temperatures were measured for five Merino rams selected for a high degree of skin fold (Folds Plus) and five selected for a low degree of skin fold (Folds Minus) at air temperatures between 20°C and 45°C. As air temperature increased, scrotal surface area of both Folds Plus and Folds Minus rams increased slightly. The greatest increases occurred at a scrotal temperature of about 36°C. At all temperatures Folds Plus rams had more pendulous scrota and larger scrotal surface areas than Folds Minus rams. Despite this, the intra-testicular temperatures of Folds Plus rams were higher than those of Folds Minus. Increasing scrotal surface area at high temperatures is one means of reducing testes temperature and maintaining fertility, but the scrotum has other more important means of thermoregulation, e.g., rate and amount of sweat loss.