All good things must end, and eventually your breeding horses won't be able to be bred anymore. The limits are much, much lower than realistic numbers (especially for stallions), but the limits are in place to prevent an excess of horses on the site, which would lead to tons of unwanted horses and a major shift in the way the grade scale works.
Normally, mares can have 3-4 foals. This is randomly determined at birth. Custom mares get +2 to their original limit, meaning they all have a limit of 5-6. If you have the skill to see limits, you'll be able to plan ahead. Otherwise, there will be an icon in Mare Services to let you know if a mare has reached her limit and is no longer able to be bred.
Mares can earn additional foal slots by using Legacy or Robin's Nests, either of which will increase her foal limit by 1. Mares who are <75% custom have a maximum foal limit of 5, while mares who are >=75% custom have a maximum foal limit of 8.
Stallions earn their foal limits by merit, rather than all studs being given essentially equal limits. Stallion foal limits are calculated as follows:
- Colts are all be born with a limit of 5 foals.
- Purchased custom colts will start with a limit of 10 foals.
- They earn a bonus of 5 to 7 foal slots when they earn 50 racing points.
- They earn an additional bonus of 5 to 7 slots when they reach 100 points.
- They then earn up to 12 additional bonus slots if they are accepted into the Stallion Incentive Program, based upon their level of acceptance. (See below.)
Thus, based on merit, a non-custom stallion can earn 27-31 foal slots. The only stallions who may exceed this limit are Pro Shop Purchased customs, stallions who were standing at stud before Year 14, or stallions who have been fed legacy. Like mares, these limits can be viewed on their Breeding Info page and also in your Stud Services.