The concentration of livestock breeding on a small number of highly productive commercial lines has reduced genetic diversity, creating welfare vulnerabilities to disease and environmental change.
The genetic homogeneity of commercial livestock populations creates systemic welfare vulnerability. A disease that spreads effectively through highly selected commercial populations can sweep through multiple farms simultaneously, causing welfare emergencies at scale. The limited genetic diversity of commercial Holstein cattle means that harmful recessive alleles carried by widely used elite sires can affect large proportions of the global dairy population before the problem is identified. Traditional breeds that developed under natural selection conditions often carry resilience traits — disease resistance, heat tolerance, better feet and legs — that commercial selection pressure has removed in pursuit of production efficiency.