Selective breeding has transformed livestock production, dramatically increasing growth rates, milk yields, and egg production over the past century. These gains have frequently come at a welfare cost, as selection for production traits can inadvertently select for conditions that compromise health and wellbeing.
Welfare Costs of Intensive Selection
Examples across species illustrate the pattern:
Broiler chickens: Rapid growth rates associated with leg disorders, heart failure (sudden death syndrome), and ascites. Breast muscle growth is disproportionate and impairs locomotion.
Dairy cattle: High milk yield creates metabolic stress, increasing risk of ketosis, lameness, and reproductive disorders. Holstein cows selected purely for production have shorter productive lives.
Pigs: Selection for leanness has been associated with increased stress susceptibility (porcine stress syndrome in extreme cases) and reduced disease resilience.
Turkeys: Breast muscle hypertrophy in commercial turkeys prevents natural mating, requiring artificial insemination. Cardiovascular problems are common.
The Welfare Trait Dilemma
Including welfare traits in breeding indices is theoretically straightforward but practically complex. Key challenges include:
Many welfare traits are difficult and expensive to measure at scale
Heritability of welfare traits is often moderate to low
Genetic correlations between production and welfare traits can be antagonistic
Industry incentive structures have historically rewarded production over welfare
Progress in Welfare-Conscious Breeding
The field is evolving. Major breeding companies now include health and welfare traits in their indices:
Cattle: Longevity, fertility, mastitis resistance, lameness resistance and hoof health increasingly weighted
Poultry: Leg health scores, cardiovascular fitness, and livability included in some broiler indices; bone strength in layer lines
Genomic selection has accelerated genetic progress and makes it more feasible to select for multiple traits simultaneously, including welfare. SNP chips allow genomic estimated breeding values (GEBVs) for traits that would otherwise be difficult to measure, including disease resistance and behavioural traits.
Regulatory & Industry Landscape
The EU Farm to Fork Strategy and updated EU animal welfare legislation place increasing pressure on breeding companies to demonstrate welfare-conscious selection. Welfare assurance schemes increasingly require producers to use approved breed lines. Consumer demand for welfare-certified products is also driving change upstream to breeding decisions.