Effect of long term ejaculation at high frequency on output of sperm, sexual behavior, and fertility of Holstein bulls; relation of reproductive capacity to high nutrient allowance.

Eighteen Holstein bulls were used to determine the long term effect of high frequency ejaculation on reproductive performance. From 1 to 7 yr of age, six bulls were ejaculated weekly, and six pairmates were ejaculated six times weekly. For comparison, six bulls were ejaculated one or six times weekly from 1 to 2 yr of age, placed on sexual rest, and then ejaculated six times weekly for 6 wk and twice daily for 14 days at 3, 4, and 5 yr of age. Six time bulls yielded 3.3 times more motile sperm per week than one time bulls. Sexual activity, which was similar for one and six time bulls, was relatively constant to 5 yr of age and then gradually decreased. Sexual rest did not affect subsequent weekly output of sperm. Postthaw motility of sperm was similar for the one time, six time, and sexually rested groups. Fertility at 4, 6, or 8 yr of age did not differ between one and six time bulls. In conclusion, continuous high frequency of ejaculation from 1 to 7 yr of age greatly increased the harvest of sperm from a bull without harming his growth, reproductive capacity, or fertility. Ten other Holstein bulls fed concentrate ad libitum from 17 wk to 2 yr of age attained puberty 2 wk earlier (37 wk of age) and yielded 1.4 times more sperm per week on six times at 3 yr of age than the six time bulls fed limited energy. Raising bulls on maximum energy allowance enables sampling in a progeny testing program by 13 to 14 mo of age.