Effect of Season on the Stallion
In both the stallion and mare season impacts reproduction. It does this by changing the secretion of melatonin from the pineal gland. Below is an example of how increasing day length during spring to summer decreases melatonin and stimulates increased GnRH. Note this effect of season and light is not the same in all seasonal species. For example in sheep it is the opposite. Many species such as humans, cattle and pigs are not seasonal and so even though melatonin changes occur, they do not impact sperm production or female cyclicity.
