Heritability of egg production in laying hens under cumulative, multitrait and repeated measurement animal models

Six generations of three layer lines (13 770 recorded individuals of A22 line, 13 950 of A88, 9 351 of K66) were used to estimate genetic effects on egg production under cumulative, multitrait and repeatability models. Variance components were estimated by the AI-REML algorithm. The heritability of cumulative records ranged from 0.08 to 0.1. For the repeated measurements model the following genetic parameters were obtained: heritability 0.02-0.03, repeatability 0.04-0.38. The first two months of egg production were found to differ from the other periods: heritability was relatively high (h2 > 0.35) and low or negative correlations with the other periods were found. Heritability was low (h2 < 0.1) from the peak production until the end of recording and the consecutive periods were highly correlated. Further studies on monthly records are suggested.