The effects of frequency of ejaculation and undernutrition on the size and tone of the ram's testes

Abstract

Replicated experiments were conducted to examine the effects of frequency of ejaculation (0, 5 or 10 ejaculations/day for 15 days; 3 rams/subgroup) and undernutrition (100%, 60% or 20% of maintenance for 28 days; 6 rams/subgroup) on the size and tone of the testes of mature Merino rams. Rams fed at 20% of maintenance experienced reductions of 15% in live weight and 35% in testicular volume. Comparable values for rams fed at 60% of maintenance were 10% and 33% respectively. Rams which ejaculated 5 times a day suffered no reduction in live weight or testicular volume. However, contemporaries ejaculated 10 times a day experienced a 10–15% reduction in testicular volume ( P < 0.01). The tone of the testes was not closely related to changes in testicular volume induced by either undernutrition or frequent ejaculation. After 15 days (the length of the shorter experiment) the reductions (means of both replicates) in testicular volume were of the order of 14% when fed at 60% maintenance, 16% when ejaculated 10 times daily, and 19% when fed at 20% maintenance. It is concluded that both undernutrition and frequent ejaculation may contribute to the reduction in testicular size (or volume) frequently observed in rams during paddock mating. It is suggested that increased physical activity may be at least partly involved in the observed ejaculation response.