The time it takes for a horse to ejaculate depends on libido. An aggressive horse will take around 2 minutes, but it may take as long as 30 minutes for an average horse.
Horses have the lowest reproductive efficiency of all species of domestic livestock and scientists guess that there is probably not a specific cause. Knowledge of the reproductive physiologies of the mare and stallion is the biggest key to successful horse breeding.
A research project carried out at The Norwegian School of Veterinary Science recently found that 50.7% of Norwegian standard bred horses suffer from joint defects caused by hereditary diseases, which should now be taken into account when breeding.