Hatchability traits as selection criteria in breeding of laying hens

The aim of the study was to determine hatchability traits that may contribute to the aggregate breeding merit of laying hens. The research concerned the performance of five generations of Rhode Island White maternal line (2,626 birds) and Rhode island Red paternal line (1,787 birds). The individual recording of breeder hen flock included the following traits evidenced during 4 (maternal line) or 3 (paternal) hatches within a year: DE discarded eggs (eggs discarded due to structure defects, shell cracks, size, contamination), FE - number of fertilized eggs, DC number of dead chicks observed during the 1(st) and 2(nd) candling of the eggs, CHL - number of healthy chicks hatched from laid eggs (set eggs and discarded eggs), CHS - number of healthy chicks hatched from set eggs, CHF - number of healthy chicks hatched from fertilized eggs, and MWC - number of hatched chicks that were classified as malformed or weak. (Co)variance components were estimated by means of the REML method using the multiple-trait repeatability animal model. Breeding value was assessed with the BLUP method. Genetic improvement of hatchability traits may successfully rely on an analysis of one indicator - number of healthy chicks hatched from eggs laid during the setting period. This trait comprises also the other reproduction indicators and, thanks to high, positive correlations with them, facilitates the use of correlated response in the genetic improvement of laying hens. In breeding work aiming at improving CHL, one can expect a higher frequency of hatching-suitable eggs, an increased fertilization rate and a decreased embryonic mortality, which are accompanied by a higher percentage of hatched healthy chicks.