In the promo image for the pack, it is claimed that horse breeding receives a "huge buff". However, the actual buff is quite tame in game. Horse Stonks, the mod that modifies horse breeding behavior, simply prevents a stat from being reduced below the worse parent. For example, breeding a 0.2 and 0.23 speed horse will never result in a horse slower than 0.2. It does this by first running the vanilla horse breeding code, then imposing the lower bound.

This does not fix the biggest issue with vanilla horse breeding, which is the third random horse that makes all breeding attempts tend towards the average horse. This issue was fixed in vanilla in 1.19.4, but obviously does not impact the modpack in 1.192.

As it stands in the Musketeer modpack, it's easy to get a horse that is similar to the ones you already have, but it is still just as difficult as in vanilla to improve the horse. For an example, if you are breeding a 0.3 speed and a 0.31 speed, in vanilla you are very likely to get a useless 0.27 speed horse. That horse would become a 0.3 speed horse in Musketeer, which is still just as useless because you already have a better 0.31 speed horse. In either case, the newly bred horse would be useless.

I propose a backport of the vanilla breeding behavior implemented in 1.19.4, or otherwise buffing horse breeding so that one can consistently improve the stats of their horse without hundreds of breeding attempts.

I'll add that I admit there is one very nice part of the mod, which is that stats don't degrade if you aren't paying attention to them. In vanilla, you pretty much have to only focus on one stat and let the others tend towards the average, as going for the fastest horses means you are waiting to get very lucky for very small speed improvements which are unlikely to coincide with jump and health improvements. With Horse Stonks, getting lucky with speed will at least keep jump and health the same, which means it is viable to breed for all stats at once. Still, the most valuable stat for most people is speed, and Horse Stonks does little to improve the experience of breeding for one stat.