Corticosterone in feathers: Inter- and intraindividual variation in pullets and the importance of the feather type

Abstract

Measuring corticosterone concentrations in feathers of poultry may be suitable to determine birds' exposure to stress. It is thinkable, that in laying hens such information could be helpful as an animal welfare indicator to evaluate adverse husbandry conditions and to predict the risk of developing behavioral disorders, such as feather pecking and cannibalism. Yet, there are some fundamental issues which remain unclear. Therefore, the objective of the current pilot study was to examine the inter- and intraindividual variation of pullets at the end of the rearing period, when most of the feathers are fully grown and animals are reaching sexual maturity. Flight feathers from both wings ( n = 4), the tail ( n = 2 – 3), and body feathers ( n = 1 pool of 3 – 5 feathers) were taken from pullets ( n = 10), genetics Lohmann Brown, at an age of 19 weeks who were reared in the same flock ( N = 728). Corticosterone analysis was performed applying a validated protocol for laying hens. Results indicate not only high intraindividual, but also high interindividual variation. Mean over all samples was 75.2 pg/mg (± 38.58 pg/mg, n = 76), showing higher intraindividual variation (between feather types; SD: 23.75 pg/mg – 49.38 pg/mg; n = 10 pullets) than interindividual variation (within feather types; SD: 11.91 pg/mg – 49.55 pg/mg; n = 6 feather types). The variation between different feather types within one bird was higher than the variation within one feather type between different birds, indicating that birds a) may respond differently when exposed to stressors and b) corticosterone measurements should be done with the same feather type.

The Effect of Egg Laying on Feather and Plasma Corticosterone Concentrations in Turkey (Meleagris gallopavo) Hens

“…Even though the FCORT concentrations of secondary 1 and 3 were significantly different within the studied lines, we found that the inter-individual variation in FCORT was larger than the intra-individual variation when looking at both periods (53-56% vs. 29%). This is contrary to what was found in chickens by Häffelin et al [23], who found that intra-individual variation was higher than the variation between birds. However, they analyzed many more feather types (scapular, tail, wing, e.tc.)…”

“…This may explain why, in the present study, the intra-individual variation (32%) is slightly greater than the variation between individuals (25-30%) during the pre-lay period since this is supposed to reflect levels of FCORT before egg production. Inter-individual variation is an important consideration when assessing how individuals respond to the same situation [23]. Our results indicate more variability in the FCORT response between birds than within birds during energetically demanding periods, which may relate to differences found between genetic lines.…”

“…Differences between feathers and feather types in terms of FCORT have been reported previously [23]; however, this is not always the case. Others found that feathers of the same type tend to have similar FCORT levels (i.e., secondary 1 and secondary 2) [9,20], whereas feathers from different body areas (i.e., back feathers and wing feathers) tend to show differences [23,40]. This is potentially because FCORT deposition in feathers can be affected by the feather's size, shape, colour, structure, and growth rate [19,40,41].…”

“…Specifically, there are demonstrated differences in the concentration of FCORT between different feathers collected from the same individual. In some cases, the intra-individual difference in FCORT can be significantly larger than the difference between individuals [23]. Significant differences between feathers can be found when the feathers are chosen from different body areas (i.e., back vs. tail feathers) [23,24].…”

“…In some cases, the intra-individual difference in FCORT can be significantly larger than the difference between individuals [23]. Significant differences between feathers can be found when the feathers are chosen from different body areas (i.e., back vs. tail feathers) [23,24]. Studies which assessed different feathers from the same area (i.e., primary feather 2 vs. primary feather 8) did not find a significant effect of feather type on FCORT levels [9,20].…”