Extent of variation within a laying flock: attainment of sexual maturity, double-yolked and soft-shelled eggs, sequence lengths and consistency of lay

1. An experiment was conducted to determine the amount of variation that exists within a population of laying hens in age at first egg, the number of birds that did not come into lay, the prevalence of soft- shelled and double- yolked eggs, sequence characteristics and consistency of lay. 2. Oviducal problems accounted for most of the poor laying performance. About a third of the flock produced double- yolked or soft- shelled eggs at the onset of lay, the proportion being influenced by the age at photostimulation. In some instances these aberrations interrupted sequences. Differences in laying performance were particularly evident in mean sequence length, mean prime sequence length and mean pause length both within and between individuals. Furthermore, sequence length did not always decline in a regular fashion with advancing age. 3. The information gathered here has been used to develop a mechanistic, stochastic population model for laying hens.