Neonatal handling of Amazon parrots alters the stress response and immune function

Abstract

The influence of neonatal handling on behavior and immune function was assessed in Orange-winged Amazon parrots ( Amazona amazonica). Chicks ( n=11) were gently handled daily from 25 days of age until 38 days post-fledging, while control chicks ( n=9) were not handled. At 10 days post-fledging (∼66 days of age), chicks were given tests to evaluate tameness (e.g., willingness to perch on an offered finger). They were then restrained for 10 min, either by being held while perching (handled group) or, because they would not perch, by being restrained in a towel (nonhandled group). Serum corticosterone levels were measured and immune status was assessed by: the delayed-type hypersensitivity (DTH) response to phytohemagglutinin-P (PH-P) injection; the humoral response to a killed Newcastle disease virus (NDV) challenge; and heterophil:lymphocyte ratio (H:L). Handled chicks were tamer by all measures of tameness. DTH was greater in nonhandled chicks ( P≤0.002), as were serum corticosterone levels (Wilcoxon, P≤0.05), while NDV antibody titers were possibly reduced ( P≤0.09). H:L ratios did not differ. We conclude that handling conditioned the birds to be held in a manner that appeared not to be stressful. The greater DTH response of nonhandled chicks suggests that either their DTH response was enhanced by the acute stress of being restrained in a towel, and/or the DTH response of handled chicks was suppressed as a result of the repeated physiologic stress from handling during the neonatal period. In either event, handling produced marked differences in response to types of restraint that would be typically encountered in the husbandry of Amazons in captivity.