Tom's Livestock Overhaul

Each of these animals spawns with a two-allele genotype, and offspring inherit one allele from each parent following a Punnett-square pattern. Each trait has a dominance weight, so the more dominant allele decides the visible coat. Breeding two animals with different traits produces young whose appearance depends on how their alleles rank against each other, and the dominance weights can be changed in the config to rebalance which genes win out.

Wild animals spawn in groups that share one trait, like real herds and flocks, rather than as mismatched litters. Where an animal spawns also matters: each trait is tied to a biome-temperature category (Cold, Temperate or Hot), and the thresholds that define those categories are configurable. Biome temperature decides which traits appear on animals that spawn naturally, and offspring from bred animals keep their inherited traits regardless of where they are born. Packing too many pigs, cows, sheep or chickens into a tight space makes them show visible distress, with particles rising off them and periodic damage the longer they stay crowded.

The mod is for NeoForge and runs on 1.21.1 only. The server and every player need it. The author holds all rights and the license does not permit redistribution, so the code is not open source.