The dark side of white hair? Artificial light irradiation reduces cortisol concentrations in white but not black hairs of cattle and pigs

Analysing hair cortisol concentrations (HCCs) is a minimally invasive way to retrospectively assess long-term stress, and its application in studies of animal welfare stress has attracted considerable interest. However, not only stress-related effects but also hair-specific characteristics external influences can affect HCCs interfere with the interpretation results. Thus, it was aim this study investigate impact daylight UV irradiation on hairs pigs cattle. We examined whether potential effect depended colour hair. For purpose, black white samples from 18 Saddleback Holstein Friesian cattle were exposed artificial light (both visible UV) compared control same animals kept dark. Exposure significantly decreased both (P < 0.05) 0.001), had an influence HCCs, showing higher levels than (cattle: P 0.001, pigs: = 0.07). The interaction between exposure significant 0.01) so reduced porcine In cattle, light-exposed exhibited lower or These results demonstrate that degrades favours elimination by structural changes matrix. detectable hair, indicating melanin pigments absorbed radiation, thereby reducing photodegradation. Compared other known influencing factors such as age body region, relatively low vitro experiment. further should under real-life conditions, outdoor indoor housing.