Restoration of reproductive capacity of stallions after suppression with exogenous testosterone.

The research investigated the effects of withdrawing testosterone propionate (TP) treatment on sperm production, seminal quality and libido in stallions. The study found that while high dosages of TP drastically reduced many sperm-related factors, these effects were largely reversible after the treatment had been stopped for 90 days.

Experimental Design

In the study, 12 stallions were chosen and divided into three groups. The groups were given no TP (control group), 50 micrograms TP per kg body weight, or 200 micrograms TP per kg body weight every other day for 88 days.

Findings

• The study found that the low dosage (50 micrograms) of TP did not cause significant changes to most of the factors studied.
• Higher dosage (200 micrograms) dramatically shrunk scrotal width, reduced sperm production, decreased the number of sperm per ejaculation, reduced the percentage of sperm showing progressive movement and also lowered the percentage of normal sperm cells.

TP Withdrawal Effects

The effects noted from the higher dosage treatment were largely reversed after the testosterone treatment was halted.

• Scrotal width, testicle weight and sperm production were back to normal in both the treatment and control groups 90 days after the TP treatment was stopped.
• The number of sperm cells in each ejaculate remained lower in the stallions that received 200 micrograms TP compared to the control group during recovery. However, the count of sperm in the extragonadal ducts normalized in all groups 90 days after recovery.
• Both sperm movement and the proportions of normal sperm were back to normal for all three groups by the end of the recovery period.
• The study also indicated that libido was unaffected by either TP treatment or withdrawal.

Conclusions

This research is significant in understanding the reversible effects of TP treatment on stallions. Knowledge of these effects, and the time period for full recovery, may be invaluable in scenarios where TP treatment is used to manage stallion behaviors or in other veterinary medical interventions.