HGG Community Forums

There is no penalty in the game for breeding horses that are related. I've seen it in the pedigrees of a fair number, especially in H&J1.

Some players try to avoid such crosses, since line breeding can be questionable in real life, especially when done to excess, because bad recessive traits can be reinforced, but there is no effect in the game. The exception is if both horses are carrying one of the potentially homozygous lethal genes--the whites, frame, sabino 1 & 2 with white 1 & 2, and now some of the splash types. Then there is a 1 in 4 chance of a dead foal. This results in a dead foal almost every time such a cross is made, although sometimes one is lucky.

The thing to remember is that you aren't guaranteed three live foals for every four such crosses you make. Every foal has an equal chance of getting a lethal doubling up on the fatal gene.