Effect of inbreeding on production traits and their genetic parameters in laying hens

Inbreeding depression in closed populations may be one reason for decreasing genetic progress. The aim of this study was the analysis of inbreeding depression on various traits for laying hens. Part period egg production traits (EN24, EN32, EN44, EN60, ENT), body weight, egg weight, egg mass, and feed intake from two brown purebred lines of a commercial breeding programme were analysed. Higher heritabilities were estimated with 10 generations pedigree information versus 3 generations pedigree information for the male line. For the female line no significant differences between heritability estimates were observed. Inbreeding depression was not critical, mainly because matings of sibs were avoided. Average inbreeding coefficient after 10 generations was for the male line 4.8% and for female line 3.9%. In the male line, significant inbreeding depressions were calculated for EN32, EN60, ENT, egg mass and feed conversion rate. In the female line only for EN24 a significant inbreeding depression was found. A possible reason may be the difference in average inbreeding coefficient between lines. Also the female line showed lower frequencies of highly inbred individual hens.