1. Genetic variables of feather pecking (FP) behaviour in a 1993 commercial pure line of White Leghorns were estimated at the age of 6, 38 and 69 weeks. 2. Heritability estimates of performing FP were 0.05 +/- 0.06, 0.14* +/- 0.07 and 0.38** +/- 0.12 for 6, 38 and 69 weeks respectively for sum of pecks (PECKS) and 0.13* +/- 0.07, 0.13* +/- 0.07 and 0.35** +/- 0.12 for sum of bouts (BOUTS). 3. Heritability estimates of receiving FP were not significantly different from 0 except at 6 weeks (0.15* +/- 0.07 and the average of the 3 age classes (AVG) (0.22** +/- 0.09) for PECKS and at 6 weeks (0.15* +/- 0.07) using BOUTS. 4. Genetic correlations of performing FP among age classes were in general high and significant. This was not the case with receiving FP. 5. Plumage cover at 51 weeks had a negative genetic correlation with performing FP at 69 weeks and AVG, but not with receiving FP. No phenotypic correlations were significant between plumage and FP. 6. Body weight at 51 weeks had a negative genetic correlation with performing FP at AVG. 7. Heritability estimates for performing and receiving FP at 6 weeks correspond to those in the literature. No estimates have previously been reported on feather pecking at 38 weeks or 69 weeks. 8. Selection of birds with no or a very low tendency to perform feather pecking should, on the basis of our results, be feasible.
