Day 21 concludes Stage 3 and the third week of production. Broilers must hit the crucial 1.0 kg milestone. Perform a rigorous 100-bird sample weighing audit, evaluate flock uniformity (CV), calculate cumulative FCR, and assess skeletal leg strength before moving into the final finishing phase.
Week 3 body weight and uniformity dictate harvest uniformity and processing yield. A flock entering Week 4 with >80% uniformity and strong bone mineralization converts feed efficiently and avoids late-stage leg defects and ascites.
•Weighing birds only near the shed doors where weights are typically non-representative of the whole house.
•Weighing birds in groups rather than individually, making it impossible to calculate true coefficient of variation (CV).
•Ignoring poor uniformity on Day 21, leading to severe processing plant rejections and weight penalties at harvest.
•Examine femurs and tibias during post-mortem: check for femoral head necrosis (FHN), tibial dyschondroplasia (TD), and rickets (pliable bones or beaks).
•Veterinary Escalation: Immediately summon veterinarian if 21-day mortality exceeds 0.1%/day, if severe lameness exceeds 1.5%, or if post-mortem shows sudden death syndrome (flip-over) with enlarged congested lungs and blood clots.
•Use a three-sided catch frame in the center of the pen to corral birds quietly without chasing or stressing the flock during weighing.
•Record weights on a histogram sheet or digital scale app to see your flock's bell curve immediately.
Weigh 100 individual birds and calculate the average weight. Determine the range of ±10% of that average (e.g., if average is 1,000g, the range is 900g to 1,100g). Count how many birds fall within this range. If 85 out of 100 birds are within range, your flock uniformity is 85%.
A minimum 6-hour dark period reduces metabolic stress, lowers incidence of ascites and sudden death syndrome (flip-over), stimulates melatonin secretion, and gives bones time to remineralize under rapid muscle loading.
Tomorrow, your operation reaches Day 22. The primary management objective will be:
Transition shed to transitional/tunnel ventilation, target 1,125g body weight (+65–70g daily gain), and maintain litter dryness under 309 ml/bird water throughput.
Benchmark Milestone Day 21 Growth & FCR Target Audit
Day 21 marks the crucial transition to grower feed. Compare your flock's actual body weight against Cobb 500, Ross 308, and VenCobb 430 standards.
