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

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Abstract
Holstein bulls (18) were used to determine the long-term effect of high frequency ejaculation on reproductive performance. From 1-7 yr of age, 6 bulls were ejaculated weekly, and 6 pairmates were ejaculated 6 times weekly. For comparison, 6 bulls were ejaculated 1 or 6 times weekly from 1-2 yr of age, placed on sexual rest, and then ejaculated 6 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 1 time bulls. Sexual activity, which was similar for 1 and 6 time bulls, was relatively constant to 5 yr of age and then gradually decreased. Sexual rest did not affect subsequent weekly output of sperm. Post-thaw motility of sperm was similar for the 1 time, 6 time and sexually rested groups. Fertility at 4, 6 or 8 yr of age did not differ between 1 and 6 time bulls. Continuous high frequency of ejaculation from 1-7 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 lib from 17 wk-2 yr of age attained puberty 2 wk earlier (37 wk of age) and yielded 1.4 times more sperm per week on 6 times at 3 yr of age than the 6 time bulls fed limited energy. Raising bulls on maximum energy allowance enables sampling in a progeny testing program by 13-14 mo. of age.