Data from a selection experiment conducted with White Leghorn lines were used as the basis for an evaluation of responses to selection for increased production and correlated responses of reproduction traits. Data on egg number (EN), egg weight (EW), percent fertile eggs (PF) and percent hatched of fertile eggs (PHF) were collected from the two lines as a part of a ten- generation experiment in which increased egg number (Lnl) and egg weight (Ln2) were selected for. Genetic trends for direct and correlated responses were calculated for each line. Direct selection for increased egg number in Lnl and egg weight in Ln2 resulted in substantial genetic gain over generations. Moreover, in the line selected for EN there were consistent positive genetic trends in terms of the PHF and along with egg number. Selection for increased egg weight, however, negatively affected PF and PHF over generations. 

A. Sewalem, K. Lillpers, K. Johansson, M. Wilhelmson

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 24: Sheep and goats (fibre); sheep and goats (meat and milk); poultry; horses; buffaloes., , 286–289, 1998
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