Hair Testosterone and Cortisol Concentrations in Pre- and Post-Rut Roe Deer Bucks: Correlations with Blood Levels and Testicular Morphometric Parameters

Abstract

Simple SummaryThe roe deer is a very common wild species in Italy and shows peculiar reproductive characteristics. Sexually-mature males, called bucks, show a complete interruption in spermatogenesis during the cold seasons. The mechanisms behind such interruption are still partially unknown. Hair is a good biological sample, easy to obtain while minimizing stress, for endocrinological analyses that may provide information regarding such mechanisms. The aim of the work was to quantify and compare hair concentrations of testosterone and cortisol in wild roe deer bucks hunted during the pre- and post-rut period (mating season). The secondary objective was the evaluation of possible correlations of such hair concentrations with blood and morphometric parameters of the testes. Testosterone significantly increased from the pre- to post-rut period, while cortisol significantly decreased. The correlations with blood and testicular parameters resemble what is already described in the literature. Overall, this study represents a first report of the quantification of testosterone and cortisol in roe deer hair, and may provide interesting insights into their reproductive physiology.AbstractThe roe deer is a seasonally breeding species with a reproductive cycle regulated by endogenous rhythms and photoperiod-sensitivity. Sexually mature bucks show hormonal and testicular activation during the reproductive season, with a peak in the rut period, and following gradual involution. Hair is a good matrix for non-invasive endocrinological analyses that provide long-term information without being influenced by the hormones’ pulsating release patterns in blood. The aim of the work was to quantify hair concentrations of testosterone and cortisol in wild roe deer bucks hunted during the pre- and post-rut period, using a radioimmunoassay methodology, and to look for differences between the two periods. The secondary objective was the evaluation of possible correlations of such hair concentrations with blood and morphometric parameters of the testes. Both hormones showed statistical differences, with opposing trends, when comparing the two periods: testosterone increased while cortisol decreased. The correlation analysis was in agreement with existing literature regarding metabolism/actions of these hormones and testicular morphometric parameters. This study represents the first report of the use of radioimmunoassay techniques to quantify testosterone and cortisol in roe deer hair, and may provide interesting insights into their reproductive physiology.

Progesterone and Cortisol Levels in Blood and Hair of Wild Pregnant Red Deer (Cervus Elaphus) Hinds

“…It is indeed almost impossible to collect repeated samples on the same animal in order to obtain a dynamic profile of specific analytes throughout the different phases of gestation. This is why collecting samples upon killing during the hunting season may represent a good, if not the only, way to perform this kind of research [19]. This study confirms the chance to collaborate with hunters and local biometric centers.…”

“…Blood was collected from the jugular vein in sterile Lithium-heparin tubes, while hair was clipped from the dorsal-caudal region of the animals. All samples were refrigerated (5 ± 1 • C) and transferred in a cooler, within 24 h, to the physiology laboratories (ANFI-ASA) of the Department of Veterinary Medical Sciences of the University of Bologna (Ozzano dell'Emilia, Italy) as previously described [19].…”

“…Cortisol (CORT) is another important hormone, generally used as stress marker also in wild animals [15], but the evaluation of its plasma concentrations is considered as poorly reliable since the hypothalamic-pituitary-adrenal axis is instantaneously activated upon stressful stimuli, such as restraint and blood sampling [16]. This is partially why, in the last years, alternative matrices for hormones' and other analytes' quantification have been proposed, including hair and feces, capable of providing different information regarding a longer timespan [17][18][19], also in red deer [20,21] and other frequently hunted ungulates [22]. For example, fecal CORT was proven to increase during late pregnancy with 10-year old females showing higher levels in comparison to five-year old hinds.…”

“…This lack of data can be partially imputed to the difficult nature of sampling. Since these animals can only be killed during certain periods of the year according to the local hunting regulation and usually undergo biometric examinations immediately after, collaborations with control centers for the collection of biometric records and hunters may help increasing the chances of sampling [19].…”

Effect of Testosterone on Antler Growth in Male Sambar Deer (Rusaunicolor unicolor) in Horton Plains National Park, Sri Lanka

“…The results obtained in the present study were absolutely in agreement with identical research work carried out in other deer species which were predominantly with temperate ancestry. The variations of testosterone level observed in this research work streamlined with the findings of many other researchers (Bubenik, Brown, & Schams, 1991; Bubenik & Schams, 1986; Muir, Sykes, & Barrell, 1988; Ventrella et al, 2018). These studies also admit that, it is the immediate drop in the testosterone concentration which element the Casting of Antler (Figure 1).…”