Divergent selection on feather pecking behavior in laying hens has caused differences between lines in egg production, egg quality and feed efficiency

The correlated changes in egg production, egg quality, and feed efficiency due to selection for or against feather pecking (FP) were investigated by analyzing the data from an experiment including two divergent selection lines and a control line. The experiment was conducted with hens at the age of 42 to 46 weeks (hatch 1) and 39 to 43 weeks (hatch 2) in the fifth generation of selection. Number of FP bouts per hour in low FP line (LP) was significantly lower than that in high FP line (HP) (0.38 vs. 2.01), and total plumage score in line LP was significantly better than that in line HP (16.9 vs. 11.6). During the four weeks, egg number and egg mass in line LP were significantly higher than those in line HP (24.4 vs. 18.3, and 1223 g vs. 1132 g). On the other hand, line HP was significantly higher than line LP in egg weight (60.7 g vs. 59.2 g), albumen height (73.0 vs. 64.9 in Haugh unit), shell thickness (38.1 cmm. vs. 37.0 cmm.) and yolk percentage (30.6 % vs. 29.5 %). The control line (C) was intermediary with respect to those traits. The residual feed consumption was significantly different between the lines, highest for line HP, lowest in line LP while intermediate in line C. Partial regressions of feed consumption on body weight gain and on egg mass were not significantly different between the three lines, while there was a significant difference in partial regression on metabolic BW (32.6 g/d in line LP, 38.0 g/d in line C and 43.4 g/d in line HP). In addition there was a significant negative regression of feed consumption per day on plumage score (-1.73 g). The adjustment for plumage score accounted for 60% of the difference between partial regressions on metabolic BW in line LP and HP. These results indicate that selection for feather pecking behavior has led to a change in egg production, egg quality and feed efficiency. The better feed efficiency in the low FP line resulted from a lower requirement for maintenance energy