A breeder flock that reaches photostimulation with poor uniformity will produce a flat, extended peak instead of a sharp one. The corrective window is in rearing, not in production.
Weigh a genuine random sample of at least two percent of the flock weekly, at the same time of day and the same point in the feeding cycle. Calculate the coefficient of variation, not just the mean; a good mean can hide two divergent populations.
Grade birds into light, standard and heavy pens when the coefficient of variation exceeds ten percent, and feed each group to bring it back onto its own target curve. Feeder space and water access are the quiet causes of most drift.
Document every intervention. Uniformity work is cumulative, and the flock record is what makes the next cycle better than the last.