Revenge of Billy the Kid (1992)

Old McDonald had a farm... and on that farm he HAD a goat.

The horny farmer McDonald has his wicked way with a goat. Life returns to normal for the family, until the goat gives birth! The mutant off spring, called Billy, is tormented by the Farmer's sons, only the daughter feels any pity for him. It isn't long before Billy, who keeps growing bigger, plans revenge..