Adrenal reactivity in lines of domestic fowl selected on feather pecking behavior.

Domestic chicken lines of the White Leghorn layer type differing in their level of feather pecking have been developed by divergent selection specifically on feather pecking behavior. This paper describes an investigation of basal level, reactivity to manual restraint and maximal adrenal response to 1-24 ACTH in breeder birds of the sixth generation of selection (S6) and their control line. Birds from the three lines had comparable basal levels of corticosterone (1.6 ng/ml, anova F(2,101)=0.62, ns), whereas males had higher basal levels than females, lsmean 1.9 vs. 1.5 ng/ml (anova F(1,103)=6.03, P<0.05). Reactivity to handling and restraint for 10 min differed with HFP birds showing higher reactivity than LFP birds, lsmean 11.0 vs. 7.9 ng/ml (t=-2.00, P<0.05), while control birds showed intermediate levels (10.2 ng/ml). Males had higher reactivity than females, lsmean 11.2 vs. 8.2 ng/ml (anova F(1,103)=3.96, P<0.05). Maximal response did not differ between lines (average 35.7 ng/ml, anova F(2,101)=1.38, P>0.05). Males had higher maximal response than females, lsmean 41.3 vs. 33.6 ng/ml (anova F(1,103)=5.77, P<0.05). The present study shows that selection against feather pecking behavior have resulted in lower levels of feather pecking as well as lower sensitivity to human handling and restraint in White Leghorn laying hen lines. From an animal welfare point of view this is a positive relationship.