1974 Reproduction  
Local heating of the scrotal contents of rams to approximately 40\s=deg\Cfor 1\m=1/2\ to2hr causes a sharp increase in the proportion of morphologically abnormal spermatozoa in the ejaculate 14 to 16 days later (Braden & Mattner, 1970) . This period of delay approximates to the epididymal passage time for ram spermatozoa (Dawson, 1958; Amir & Ortavant, 1968) , and has been cited as evidence that spermatozoa undergoing epididymal passage at the time of heating are resistant to damage (Braden &
more » ... damage (Braden & Mattner, 1970) . In the present study, observations were made of the changes in the fine structure of ejaculated ram spermatozoa after mild scrotal heating. Four mature Saxon Merino rams which produced good quality semen were restrained in metabolism cages. The scrota of three of them (Rams A, B and C) were immersed for 2 hr in a circulating water-bath at approximately 41\s=deg\C. The fourth ram (D) received identical treatment but the water-bath was at 34\s=deg\C. Semen samples were collected by electroejaculation immediately before scrotal heating and on the days shown in Text- fig. 1 . The motility of each ejaculate was estimated immediately after collection, and the percentages of live and abnormal spermatozoa were estimated from prepared slides (Hancock, 1957) . Spermatozoa were fixed for electron microscopy in a freshly prepared mixture of equal parts of phosphate-buffered, 10% gluteraldehyde solution and picric-formaldehyde solution (Stefanini, DeMartino & Zamboni, 1967) . The spermatozoa were concentrated (Stefanini et al, 1967) , post-fixed in 1% osmium tetroxide solution, dehydrated in ethanol, and embedded in Durcupan\x=req-\ ACM (Fluka A.G., Switzerland). Fine structural abnormalities of spermatozoa were described from ejaculates of Ram A. The percentage of spermatozoa with abnormal acrosomes was counted in ejaculates prepared for electron microscopy. At least 200 spermatozoa cut in sagittal section were assessed in each ejaculate examined. Three of the rams appeared to be in good health throughout the experi¬ ment. Ram suffered a swollen prepuce and scrotum due to harness pressure. This was first noted on Day 4 after heating, and persisted for 8 days. Abnormal spermatozoa seen in light microscope examination of semen in the present study were similar to those described by Lagerlöf (1934) . Their * Present address :
doi:10.1530/jrf.0.0400191 pmid:4416274 fatcat:dtahq6aafrhetnh5up2fhes73u