As stated in the bug report for horse breeding, and with considerable research, it is impossible to breed a horse to be better than the best possible spawned horse.

What this means, is if you find a horse with 30hp (15 hearts) you will NEVER be able to breed it with another natural horse to get anything better. This is due to the way the current breeding mechanics work.

(A B C)/3 = Child

What this means, is that for each breeding, the game takes Horse A's stats, Horse B's stats, rolls a random Horse C, adds them together and divides the total by 3. So because a newly spawned horse is capped in its categories, any bred horse will never exceed them. The best you could hope for is to breed 2 30hp horses and get VERY lucky to have your random horse stat be 30hp and you would only then result in a 30hp child, all other cases the child will be less than the two bred parents' maximum potential ^{[if they top the natural spawn stat charts]}

Conversely it also means that if the two bred horses are REALLY terrible, the random horse stat will make the child MUCH better than the parents up to a point (the average horse) ... the child will be better, but only because its stats are closer to an average horse ... and the parent's stats are terrible...

so to avoid all of this jumping around variability in breeding stats, I'm proposing a new algorithm

(pA pB)/2*R

pA=Parent A

pB=Parent B

R=Random # between 0.x and 1.x (to limit variability of child scores from parents, I suggest 10%[0.9 to 1.1])

Lets go with Block Jump

Parent A = 3 Blocks

Parent B = 4 Blocks

R = 1.05

(pA pB)/2*R

(3 4)/2*1.05

Child has Jump of 3.675