THE COMPARATIVE EFFECTS OF UNDERNUTRITION, EXERCISE AND FREQUENCY OF EJACULATION ON THE SIZE AND TONE OF THE TESTES AND ON SEMEN QUALITY IN THE RAM

The effects of undernutrition (100% or 10% of maintenance), exercise (walking 0 or 10 km day(-1)) and frequency of ejaculation (0, 4, 5 or 8 times daily) on the size and tone of the testes and on semen quality were studied in a total of 65 Merino rams in four experiments of 14-36 days duration. Testicular volume was reduced by 18 days of exercise (11-16%; P<0.05) or undernutrition (20-26%; P<0.01), and the effects were additive. Exercise for an additional 18 days led to a further decline of only 5% (NS); cessation to a 15% recovery (P<0.05). Ejaculation had no effect on testicular volume at either the 100% or 10% feeding levels. Testicular tone was not affected by undernutrition or ejaculation, but increased (24-88%; P<0.01) during 18 days of exercise. An additional 18 days of exercise caused tone to increase a further 9% (P<0.05). After exercise, tone declined by 11% over 18 days (P<0.05). Ejaculation per se decreased semen volume (25-53%; P<0.01), motility (19-36%; P<0.01), density (19-55%; P<0.01) and sperm per ejaculate (42-85%; P<0.001). Exercise caused smaller reductions in semen volume (10-25%; P<0.05), but in semen density only after 36 days (24-30%; P<0.05). The effects of under-nutrition on semen (less than 14%) were non-significant. Overall, the results indicate that reduced feed intake had a greater effect than exercise on testicular volume, and that exercise alone was associated with increased testicular tone. Ejaculation per se had no effects on either testicular volume or tone, but was the dominant influence on semen quality.