SEMINAL DEGENERATION IN THE RAM AND ITS RELATION TO THE TEMPERATURE OF THE SCROTUM

Abstract

Summary. The semen collected from twelve Merino rams was examined before and after they were exposed during 3 days to two 6-hr periods in a climate room at 40·5° C, 8·5 mm Hg vapour pressure and 40·5° C, 31·5 mm Hg, respectively. Semen of decreased quality was collected from all the rams after this treatment. The change varied markedly in severity and duration and was related to the rise of the temperature of the subcutaneous tissue of the scrotum measured during the climate-room treatment and not to changes in rectal or flank-skin temperatures. The first ejaculate containing abnormal spermatozoa was collected 13 to 21 days after the treatment, and the concentration and total content of fructose in the semen of all rams started to rise at this time. The three rams which were most severely affected suffered a seminal degeneration which lasted for 35 to 39 days. After recovery from the first experiment, the same rams were divided into three groups of four. Two groups were exposed to the same heat treatments as before and the third group stood in the climate room for 12 hr at 21° C and 6·8 mm Hg vapour pressure. Water at 17 to 19° C was circulated around the scrotum of one group of rams exposed to heat and of the group in the thermo-neutral environment. Only the rams exposed to heat without their scrota cooled in this way produced semen of inferior quality. It was concluded that under the conditions of these experiments, the efficiency of the heat-dissipating properties of the scrotum alone decided the magnitude of the adverse effects of short periods of raised air temperature on the quality of the semen produced by Merino rams.