Adrenocortical activity, measured via feather corticosterone, affects semen quality but not blood plasma prolactin in the capercaillie (Tetrao urogallus L.)

Abstract

Capercaillie populations are experiencing worrying decline in several European countries, better knowledge of the factors affecting their reproductive success is therefore much needed. Chronic stress is a major cause of infertility in wild animals used in ex situ conservation programmes. In birds, the main hormonal stress response is an increase in corticosterone (CORT) secretion. Prolactin (PRL) is also involved, but its role in sperm functionality in birds is not well known. This work reports the relationship between CORT and PRL, and their influence on capercaillie semen quality. Feather CORT concentrations were determined by ELISA, along with blood plasma PRL by radioimmunoassay, in 14 sub-adult (1–2 years old) and 5 adult (> 3 years old) capercaillies. Sperm concentration was determined using a Neubauer chamber. Nigrosin-eosin dye was used to examine sperm viability; DNA integrity was assessed via the TUNEL assay. A significant, negative correlation was detected between CORT and sperm concentration (rs = 0.30, p = 0.02), while a positive correlation was detected between plasma PRL and DNA integrity (rs = 0.78, p = 0.007). No clear association was found between CORT and PRL (rs = 0.49, p = 0.21). These results suggest that the CORT concentration provides a suitable biomarker of stress in capercaillies, a factor known to affect reproductive function in males of this species.

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