[CJ808]

I think it happens in quite a few species as the growth plates stay open longer. I’ve seen some Castrated male cows get very tall. I’m not sure the author knew much about horses as they kept referring to them as race horses. Gem Twist was a Show jumper. Cloned horses are banned from racing and race horses from using AI for that matter.

[msrenee]

I guess that's the weirdest part. The guy that referred to Gem Twist as a racehorse does artificial insemination for horses as a profession. So the basis of his career is horse breeding. He conflates racing and show jumping and either doesn't happen to mention the most obvious explanation for the size difference or is not familiar enough with horses to be aware of it. I believe I was 12 when I learned that a gelded horse tends to grow bigger than they would if they were left a stud. I honestly googled it to make sure it's not just one of those things that everyone "knows" that has no basis in fact. Difference in feed is another likely explanation that wasn't even mentioned. Why would you go to the size of the dam and the length of gestation when there's two obvious possibilities that are common knowledge to anyone who has horse experience? The quote makes it seem like it's some kind of surprise that genetics isn't the only contributor to size, but anyone who has any horse experience can tell you there's a number of other factors that determine adult size.