Skin folds and Merino breeding. 5. Variations in scrotal, testis, and rectal temperatures as affected by site of measurement, acclimatization to heat and degree of skin fold

Abstract

In Merino rams, subcutaneous temperature in the scrotum declined from the inguinal border to the distal tip and from posterior to anterior. Testicular temperature was similar at several sites in both testes. Of the total increase in scrotal and testicular temperatures that occurred when rams were heated, the proportional hourly increases were similar at each air temperature above 30¦C irrespective of the air temperature regime (stepwise increasing or stepwise decreasing air temperatures) or fold type of the ram. The response of rams depended markedly on the air temperature regime. When air temperatures were decreasing, rams were less able to withstand high temperatures and more able to withstand low temperatures. When air temperatures were increasing the reverse was true. The differences between Folds Plus and Folds Minus rams also depended markedly on the ail temperature regime. In general Folds Minus rams had lower rectal temperatures than Folds Plus rams, but could express their ability to maintain lower subcutaneous scrotal temperatures than Folds Plus rams only after they had gained a degree of acclimatization to heat. Folds Plus rams had higher food intakes than Folds Minus rams which may be a factor in their reduced heat tolerance.