Use of infrared thermography to assess laying-hen feather coverage

Infrared thermography (IRT) was compared with the traditional 4-scale feather scoring (FS, with 1 representing the worst feather coverage and 4 the best) method for assessing feather coverage of laying hens. The feather coverage of 6 body parts (head, dorsal neck, front neck and crop, back, breast, and belly), body surface temperature distribution, and relative change in sensible heat loss of 60 laying hens (Lohmann SL white breed) at 28, 56, or 73 wk of age (20 hens per age group) were compared by using IRT. For all the 6 body parts and the area-weighted overall, the area of excellent feather (EF) determined by IRT was positively correlated with the 4-scale scores determined by FS (P < 0.05), whereas the areas of fair feather (FF), no feather (NF), and body surface temperature were negatively correlated with FS scores (P < 0.05). Feather deterioration occurred for elder hens at all body parts. Feather coverage of the hens was classified as 98.7% EF, 1.3% FF, and 0% NF at 28 wk of age; 70.2% EF, 20.6% FF, and 9.2% NF at 56 wk of age; and 35.4% EF, 17.1% FF, and 49.5% NF at 73 wk of age. As a result of less feather coverage and higher surface temperature, sensible heat loss was speculated to be higher for 56- and 73-wk-old hens than for 28-wk-old hens, potentially leading to higher feed-to-egg conversion for the elder hens. It was concluded that IRT is a promising technique or tool that may provide a more objective and quantitative evaluation of laying-hen feather conditions and delineation of bird thermoregulation.