The Amish don't know the word 'genetics.' But they've practiced selective breeding for 300 years — and results speak for themselves.
Principle
Best bull (more milk from his daughters, calm, healthy) + best cow (high yield, easy births, good temperament) = offspring better than both. From offspring — keep the best. Repeat for 300 years.
Selection Criteria
Bull: not by beauty — by daughters' productivity. Amish keep oral records (who from whom, how much milk). Aggressive ones — to meat, no discussion. Sick ones — don't breed.
Exchange
Communities exchange bulls and stallions (prevent inbreeding). Livestock auctions are important social events. Purebred bull: $3,000-10,000.
Result
Amish dairy cows give comparable yields to commercial — while eating less (no grain finishing), living longer (less stress), and calving easier. Practical selection → hardy, healthy animals. Not maximum productivity, but optimal.