Babies are so cute! There are too many!
A mare is sexually mature at about 18 months of age and can remain fertile well into her later years – 25-35. If they have access to a stallion, mares will breed naturally yearly. So, it is possible that one mare can be expected to produce more than 20 new horses during her lifetime.
The best studies estimate that there are approximately 170,00 unwanted horses in the Unites States each year. Unwanted Horse Coalition / American Horse Council. http://www.unwantedhorsecoalition.org/uhc-materials/ Some die lonely deaths unnoticed, some are put down, some end up in rescues and sanctuaries. Approximately 150,00 are shipped over our borders to slaughter. http://www.aspca.org/animal-cruelty/horse-slaughter Nuf said.