The aim of the study was to determine trends for genetic and production parameters in a population of New Hampshire N-11 laying hens over 8 generations. Individual performance testing included body weight at 33 weeks of age (g), egg weight at 30 weeks of age (g), age at puberty expressed as days of age at first egg (days), and number of eggs laid to 39 weeks of age. As a result of implementing the genetic improvement programme based on NOVASEL electronic data processing system, egg production was increased, age at first egg was advanced and body weight of the chickens decreased in the N-11 line. The analysis of estimates of effective population size (Ne) and coefficients of inbreeding (Fx) shows that the cockerel and hen mating system used for reproduction effectively protects the population from an increase in inbreeding.

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