The effect of temperature on characteristics of semen of rams

Abstract

The effect on a number of semen characteristics of exposure to four periods (4, 6, 9, and 13.5 hr) of high temperature (41¦C) was studied in nine rams. Individual rams varied in their susceptibility to seminal degeneration, and repeatability within rains at successive heat treatments was low. There were significant linear effects of duration of heat treatment on volume, density, number of spermatozoa per ejaculate, percentage of abnormal spermatozoa, motility, fructose concentration, and reaction time. There was a significant effect of week of collection after treatment on all characteristics. The major component of this effect was quadratic, showing a degeneration and recovery pattern. Evidence of degeneration appeared at approximately the 12th day and reached its maximum at the 19th day, after which recovery was shown up to the 30th day. This pattern was observed in most of the characteristics studied. There was a significant negative correlation (r = -0.593 ; P < 0.01) between a mean semen composite score and the maximum subcutaneous scrotal temperature recorded during the corresponding heat treatment period. Correlations between mean semen composite score and the increase in scrotal temperature (r = -0.22) and the minimum difference between body and scrotal temperature (r = +0.33) were not significant. Thus, the maximum subcutaneous scrotal temperature appears the important factor involved in seminal degeneration following exposure to high temperature.