Rapid growth by genetic selection
Modern broiler chickens reach slaughter weight (5-6 pounds) in 6-7 weeks from day-old chick, compared to 12-16 weeks for slower breeds 50 years ago. This acceleration comes from intensive genetic selection for fast growth rate and feed efficiency.
At 1 day old, chicks weigh 40 grams. By week 3, they weigh 1-1.5 pounds. By week 6, they reach 5-6 pounds (slaughter weight). This exponential growth curve is unsustainable long-term: continued growth causes skeletal problems, heart stress, and early mortality.
Nutrition and environment management
Broilers are fed high-protein feed (18-24% crude protein) continuously to support rapid muscle growth. Water is always available. Temperature is strictly controlled: 95F at day-old (under heat lamps), reducing 5 degrees weekly to ambient temperature by week 4.
Stocking density is dense (6-8 birds per square foot) to maximize space efficiency, but this requires excellent ventilation and litter management (dry bedding). Poor conditions spread respiratory disease quickly through crowded flocks.
Production economics and welfare tradeoffs
The fast 6-week cycle is economical: turnover is rapid, amortized costs are low, and feed efficiency is high (converting 1.8-2 kg feed per 1 kg body weight gain). A single-shed farm (25,000 birds) produces 8-9 flocks per year, generating stable income.
The intensive system prioritizes speed and efficiency over individual bird comfort. Broilers have joint and cardiac stress from rapid growth; some cannot walk normally by week 6. Alternative slower-growing breeds take 10-14 weeks, eat more, and cost more but are hardier and have fewer welfare problems.