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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.
Wolc et al. (Fri,) studied this question.