Curious, how big of a size difference between mare and stallion?

[TheJenners]

I mean we see the oopsies all the time on Facebook, someone’s pony mare was exposed to someone’s yearling colt “accidentally,” but what size difference would you as an educated breeder consider the safe zone for size difference between mare and stallion? I know some sporthorse breeders who regularly breed Connemara mares to WB stallions.

Purely curious, stop giving my pony mare side eyes

[exvet]

For me it’s not just about height but also is the mare a maiden and whether or not the stallion and mare are of similar type. For example I repeatedly bred my 15 hand stallion to my 13 hand mare. Both are welsh cobs. I never had an issue with size of the foal or a difficult delivery with that cross. I would not breed the same stallion to my son’s 14 hand maiden arabian because though being heavily crabbet she did not share the same stout body type as my stallion. I was too concerned that such a cross might result in a dystocia.

[cardinale]

No direct experience, but I did see on CL the other day the yearling product of Andalusian stallion x mini/sm pony mare. Big head, stocky build, looked about 10 hh.

[TheJenners]

Yikes!!

[dani0303]

I know a breeder using warmblood stallions on her medium pony mare. The mare has had 3 such foals with no issues

[JB]

We know through the Shetland/draft studies that the uterus determines the size of the foal at birth.

We also know that doesn’t account for a foal with huge shoulders relative to his body size, or the width of the mare’s pelvix. Lots of “normal” sized foals have larger shoulders, and/or the mare has a narrower pelvis, which causes problems (sometimes catastrophic).

First foals tend to be smaller.

Would I use a 17h stallion on a 12h mare? No.
17h on a 14.2h mare? Sure, unless the stallion is known for producing foals with large shoulders. This is a “sure” from a size safety perspective, but in reality I probably wouldn’t UNLESS that stallion has adult offspring from similar sized mares so I could see how proportions generally worked out.