Sex differences in stress responses to transportation in goats: Effects of gonadal hormones

Abstract

The present study examined sex differences and the involvement of gonadal hormones in stress responses caused by road transportation in Shiba goats. In experiment 1, we investigated the stress responses of males and females to transportation. Plasma levels of cortisol (Cor) significantly increased during 1 h of transportation, and those in females were significantly higher than those in males. Plasma glucose (Glu) and free fatty acid (FFA) levels also increased similarly in both females and males by transportation, and there were no sex differences. Food intake following transportation decreased only in males compared with that in the basal session, in which the animals were not transported. Experiment 2 examined the involvement of gonadal hormones in stress responses to transportation using castrated males. Goats were given cholesterol (Cho), 5α‐dihydrotestosterone (DHT) or 17β‐estradiol (Es). The plasma Cor levels increased during transportation regardless of hormone treatment, and those in DHT treated goats were significantly lower than those in Cho or Es treated animals. Plasma Glu and FFA levels also increased during transportation, regardless of hormone treatment, and there were no differences between treatments. Food intake following transportation was significantly lower than that in the basal session only in goats given DHT. In conclusion, gender affects Cor secretion that is increased by transportation and the decrease of food intake following transportation in Shiba goats, and the major cause of these differences is androgen.

Effects of Androgen on Plasma Levels of Adrenocorticotropic Hormone and Cortisol during Transportation in Goats

“…Although plasma Cor levels increase during road transportation in both male and female mature goats, those in males are significantly lower than those in females. We further demonstrated that the increase in plasma Cor levels during transportation was significantly reduced by 5α-dihydrotestosterone (DHT) in castrated male goats [1]. In addition, we have found that ovariectomized female goats show a similar response to DHT (unpublished data).…”

“…The first or the second group was used for the experiment between April-June or October-November, respectively. The detailed transportation procedure is described in our previous work [1]. Briefly, the experiment was performed as follows: On the day of the basal session (BS), in which animals were housed and fed as usual, 2 ml blood samples were collected at 9:00, 9:15, 9:30, 9:45, 10:00, 10:30, 11:00 and 13:00.…”

“…67(11): 1109-1114 Gonadal hormones can influence the stress responses of the hypothalamo-pituitary-adrenal (HPA) axis in rodents [6,7,11], humans [10,18,19] and domestic animals [1,4]. For example, our previous work indicates that androgen affects the increase in plasma cortisol (Cor) level induced by road transportation stress [1]. Although plasma Cor levels increase during road transportation in both male and female mature goats, those in males are significantly lower than those in females.…”

“…For example, our previous work indicates that androgen affects the increase in plasma cortisol (Cor) level induced by road transportation stress [1]. Although plasma Cor levels increase during road transportation in both male and female mature goats, those in males are significantly lower than those in females.…”

“…The physiological mechanism(s) of the suppressive effect of androgen on plasma Cor level during transportation in goats [1] is not clear. Two possible mechanisms of this effect of androgen are a reduction in the ACTH secretion in response to stress, or a reduction in the responsiveness of the adrenal cortex to ACTH.…”