The object of this research was to study the relationship between feather pecking and open-field activity in laying hens at two different ages. A population of 550 birds of a laying hen cross was subjected to an open-field test at 5 and 29 weeks of age and to a social feather pecking test at 6 and 30 weeks of age. Factor analysis was used to identify underlying factors for each test: pecking behavior (social test) and open-field activity (open-field test). In young birds, a positive phenotypic correlation of 0.24 was found between high open-field activity and high levels of pecking behavior (ground pecking, preening, gentle feather pecking, and wall pecking). In adults, a similar genetic correlation of 0.62 was found. At adult age, the factor pecking behavior consisted mainly of gentle and severe feather pecking. Between ages, a strong, negative genetic correlation of -0.65 was found between open-field activity at young age and pecking behavior at adult age, indicating that open-field activity levels in young birds may predict pecking behavior in adult hens.

The aim of this study was to investigate the changes in immunological parameters as well as changes with respect to plasma levels of serotonin and tryptophan in lines selected for and against feather pecking (FP) behavior [high FP (HP) line and low FP (LP) line] for 5 generations. The hens from the HP line had a higher plasma serotonin level than those from the LP line (0.059 vs. 0.037 micromol/L, F(2,27) = 0.031, P < 0.05). The plasma level of tryptophan was, on average, 67.30 micromol/L and did not differ between the lines (68.3 vs. 66.3 micromol/L, F(2,28) = 0.36, P < 0.05). The HP line had a higher response to infectious bursal disease virus vaccination after 1 wk post-vaccination compared with the control and LP lines. The number of white blood cells (P < 0.0001) and the expression of MHC class I molecules on CD4 (P < 0.02), CD8beta (P < 0.006) and on B cells (P < 0.03) were highest in the LP line compared with the control and HP lines. Selection for or against FP, therefore, changes the number of white blood cells and the expression of MHC class I molecules on T and B cells, which may influence the health status of the birds.

In the European Union, legislation concerning animal housing is becoming stricter because of animal welfare concerns. Feather pecking (FP) in large group housing systems is a major problem. It has been suggested that corticosterone (CORT) response to manual restraint as a measure for stress is associated with FP behavior. The aim of the current study was to identify QTL involved in FP behavior and stress response in laying hens. An F2 population of 630 hens was established from a cross between two commercial lines of laying hens differing in their propensity to feather peck. The behavioral traits, measured at 6 and 30 wk of age, were gentle FP, severe FP, and aggressive pecking. Toe pecking was measured at 30 wk of age and CORT response to manual restraint was measured at 32 wk. All animals were genotyped for 180 microsatellite markers. A QTL analysis was performed using a regression interval mapping method. At 6 wk of age, a suggestive QTL on GGA10 was detected for gentle FP. At 30 wk of age, suggestive QTL were detected on GGA1 and GGA2 for gentle FP. A significant QTL was detected on GGA2 for severe FP. At 32 wk of age, a suggestive QTL was detected on GGA18 for CORT response to manual restraint. In addition, a suggestive QTL was detected on GGA5 with possible maternal parent-of-origin effect for CORT response.

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The objective of the current study was to estimate heritabilities (h2) of feather pecking and open-field response of laying hens at two different ages. An F2 cross, originating from a high and a low feather pecking line of laying hens, was used for the experiment. Each of the 630 birds of the F2 cross was subjected to an open-field test (individual, 10 min) at 5 and 29 wk of age and to a social feather pecking test (groups of five birds on wood shavings, 30 min) at 6 and 30 wk of age. Both tests were performed in a square open field (1.25 x 1.25 m). Behavior was recorded directly from a monitor. Heritabilities of feather pecking and open-field behaviors were calculated. In the open-field test at 5 wk of age, high h2 were found for most traits, ranging from 0.20 for the frequency of flying to 0.49 for number of steps. In the social test at 6 wk, gentle feather pecking (0.12) and ground pecking (0.13) were found to be heritable. When both tests were repeated at 29 and 30 wk of age, h2 estimates were lower for the open-field test, ranging from 0.10 for duration of sitting to 0.20 for latency to first step. In the social test, however, higher h2 estimates of 0.15 for gentle feather pecking and 0.30 for ground pecking were found compared with 6 wk of age. In conclusion, gentle feather pecking and open-field behaviors may be used in selection against feather pecking.