Genetic control populations: A study of efficiency of six poultry control strains

Synopsis

The aim of the experiment was to examine the efficiency of pedigreed random‐bred control populations. It was argued that it was difficult to achieve this aim by the study of the parameters of a single control population, but that a comparison of the contemporaneous performance of two or more control strains over several generations would be more appropriate.

Six pedigreed randombred control populations with a planned size of 50 males and 150 females and derived from different base populations representing strains involved in a commercial poultry breeding programme were recorded for eight generations. Some difficulty was experienced in maintaining the populations to the size planned, particularly the Wyandotte strain, and this was associated with low semen production from males and low egg production from females rather than from poor fertility or hatchability. Analysis of data on sexual maturity, 25‐week body weight and 300 days’ egg production indicated no obvious regular changes in mean or variance except for sexual maturity for which the within strain variance increased markedly. The differences between strain means stayed relatively constant and there were few changes of rank order. The intra class correlation, corrected for changes in variance, for strains between years was 0–92, 1.00 and 0.96 for sexual maturity, body weight and egg production respectively.

Heritability estimates on four of the base populations indicated large differences between strains but also that additive genetic variation for some traits in some strains was approximately zero. For such traits and strains, genetic drift cannot occur which is a most desirable feature of a genetic control population. Some data were available on crosses of the control strains, which had been recorded for egg production and laying house mortality on many farms in each of eight years. There were no regular changes between years in mean egg production but mortality

Notes

The data, on which these analyses are based, were collected whilst both authors were members of the Research Division, Thornber Bros. Ltd, Mytholmroyd, Yorkshire.