Livestock genetic selection has prioritized production traits at the expense of health and welfare, but breeding programs increasingly incorporate welfare-relevant health traits.
Livestock genetic selection for production traits without adequate weighting of health has created populations with systemic welfare problems. High-yielding dairy cows experience metabolic stress from milk production exceeding their physiological capacity. Extreme muscle development in continental beef breeds causes difficult calving requiring routine caesarean section. Broiler chickens bred for extreme growth rates have skeletal and cardiovascular problems. Modern pig sows with extreme litter sizes produce more piglets than they can rear without human intervention. Breeding organizations are increasingly incorporating welfare-relevant health traits including fertility, lameness resistance, and immune function into selection indexes. Economic indexes that include health costs incentivize selection for healthier animals that are also more profitable long-term.