Day 28 marks the end of Week 4 and the core of Stage 4. Broilers have multiplied their Day 1 placement weight by more than 40 times, reaching an average of 1,725g. Total flock biomass reaches peak density (24–28 kg/m²), making leg soundness, skeletal strength, and breast meat conformation decisive for final profitability.
•Weighing only birds near the shed entrance or catching only easy-to-catch slow birds, producing a falsely skewed low average weight.
•Skipping leg soundness evaluations, ignoring progressive skeletal issues that worsen rapidly in heavier birds during Stage 5.
•Pushing growth excessively with 24-hour continuous lighting, which causes leg weakness, ascites, and sudden death syndrome.
•Failing to calculate actual cumulative FCR at Day 28, losing the opportunity to make corrective management adjustments before final harvest.
•At 1.7kg, skeletal mineralization must support rapid muscle accretion. Leg weakness is often multifactorial: bacterial chondronecrosis (BCO), viral arthritis (Reovirus), or nutritional imbalances. Maintain dry litter and adequate dark periods (6 hours) to stimulate bone remodeling.
•Clinical escalation trigger: If lameness exceeds 5% or if cull rate spikes >0.15%/day due to leg deformities or ascites, submit lame bird cull samples for femoral head necropsy and bone histology.
•Use a proper three-sided catching frame to enclose a random group of 30–40 birds in each section. Weigh every single bird inside the frame—do not pick and choose, otherwise your sample will not represent the true shed average.
•Check the breast muscle: a good 1.7kg broiler should have a firm, wide breast that feels like a solid block of meat with no indentation or sharpness along the breastbone.
Key benchmarks include: Body Weight 1,725g (±50g), Cumulative Feed Intake ~2,550g per bird, Cumulative FCR 1.48–1.52, Livability >97.5%, and Flock Uniformity CV < 9.0% (≥80% of birds within ±10% of mean weight).
Partial thinning (or 'thinning out') involves harvesting 20–25% of the heaviest birds (typically fast-growing males) at Day 28–32 for smaller whole-bird markets (1.6–1.8kg). This immediately reduces shed stocking density, lowers metabolic heat, and provides extra feeder/drinker space for the remaining flock to grow to 2.5–3.0kg.
Providing a continuous 6-hour dark period stimulates natural melatonin secretion, which regulates growth hormone and promotes strong bone and cartilage mineralization. Continuous 24-hour light causes irregular rapid growth spurts that overload immature skeletal frames, leading to leg deformities and lameness.
