Does enhancement of specific immune responses predispose laying hens for feather pecking?

To mimic airborne immune challenges, layer hens were intratracheally and concurrently challenged with various doses of the protein antigen human serum albumin (HuSA) and the pathogen-associated molecular pattern lipopolysaccharide (LPS) at 7 and 13 wk of age. All groups received 1 similar dose of HuSA plus LPS at 11 mo of age. Evaluation of plumage and body condition at 12 mo of age revealed that birds that had undergone intratracheal immunization with a high dosage of HuSA, irrespective of the concurrent dose of LPS, had significantly more feather damage but less wounds to the vent region, as opposed to birds not receiving HuSA. On the other hand, a high dosage of LPS was related to comb damage. These results suggest that stimulation of specific (humoral) immune responses (to HuSA) rather than innate responses (to LPS) at a young age may predispose layers for feather pecking (FP) behavior at later ages. Involvement of immune mechanisms in FP or vent damage may differ. Predisposal for FP behavior by specific immunity can have consequences for health and vaccine management.