Selecting Merino rams for ability to withstand infertility caused by heat. 1. Anatomy and functional activity of the scrotum

Merino rams selected for (Folds Plus) and against (Folds Minus) skin wrinkle have been used in a study of scrotal heat tolerance. The type selected against skin wrinkle (Folds Minus) showed a higher scrotal fluid loss and sweat gland and fibre density than the Folds Plus type. Folds Minus rams had smaller scrotal sweat glands which discharged more frequently than those of the Folds Plus rams during early periods of scrotal heating. Scrotal heat tolerance was seen to increase with increases in scrotal surface area. These findings are discussed in terms of the light they shed on the problem of identifying the features that characterize high scrotal heat tolerance in Merino rams