Influence of ejaculation frequency of stallions on characteristics of semen and output of spermatozoa.

The study investigates the effects of different ejaculation frequencies on sperm reserves and output in stallions, finding that specific frequencies have distinct impacts on sperm characteristics. The research also suggests practical ejaculation frequencies for inseminating mares and long-term storage of stallion semen.

Stabilization of Extragonadal Sperm Reserves

• It took approximately 1 week to stabilize the extragonadal sperm reserves in stallions that were ejaculated daily for 10 weeks.
• The true daily sperm output of a stallion was found to be equal to the mean daily sperm output of seven ejaculates, with a variation of +/- 1-35 x 10^9 spermatozoa.

Effects of Different Ejaculation Frequencies

• Mean concentrations of spermatozoa per milliliter and the number of spermatozoa per ejaculate were higher for frequencies of once (X1) and three times (X3) per week compared to six times (X6) per week.
• Sperm output per week was nearly identical for the X3 and X6 frequencies and higher than the X1 frequency.
• An increase in ejaculation frequency from one to two ejaculates per day twice weekly significantly raised the output of spermatozoa per week.
• Gel-free semen volume, spermatozoa per milliliter, and the number of spermatozoa per ejaculate were higher in the first ejaculate compared to the second.

Practical Recommendations

• Collection of semen on alternate days is suggested as a practical ejaculation frequency for inseminating mares. This approach would align with the observed effects of different frequencies on sperm characteristics.
• For long-term storage of stallion semen, two ejaculates collected twice a week is recommended as a practical frequency. This recommendation takes into account the observed increase in sperm output with this frequency.

Implications

• The findings of this study provide valuable insights into the management of stallion reproduction, particularly in understanding how different ejaculation frequencies affect sperm characteristics.
• The practical recommendations for insemination and long-term storage can be directly applied in equine breeding practices to optimize reproductive success.