Genetic relationships among time of egg formation, clutch traits and traditional selection traits in laying hens

In a population of Rhode Island White hens heritability of egg formation, clutch characters and traditional selection traits as well as the genetic and phenotypic correlations between them were estimated via multitrait animal model. Over 1300 birds and about 4000 birds were recorded in two consecutive generations for oviposition time and traditional traits, respectively. The heritability estimates obtained for classical selection criteria: age at first egg (h²=0.42), egg weight (h²=0.50) and body weight (h²=0.42) were considerably higher than those for egg production traits: initial egg production (h²=0.22), clutch traits (h² between 0.11 and 0.23) and oviposition time (h² between 0.13 and 0.19). Both genetic and phenotypic correlations between clutch traits and traditional selection traits were low, except for initial egg production and maximal clutch length (r_g=0.40 and r_p=0.38). As expected, negative correlations were registered for number of clutches and average clutch length. It indicates an opportunity of selection aimed at improvement of egg production persistence by an increase in the average clutch size. Oviposition time was favourably correlated with traditional selection criteria.