Effects of prenatal handling stress on adrenal weight and function and behaviour in novel situations in blue fox cubs ( Alopex lagopus)

Abstract

Prenatal stress is known to affect the morphology, physiology, and behaviour of rodent offspring. This study investigated the effects of a 1-min daily handling stress given to farmed blue fox females in the last third of gestation on adrenal weight and function in male and female offspring and on behaviour in novel situations. In 10-day-old cubs ( n=68), records were made of serum adrenocorticotropic hormone (ACTH), progesterone and cortisol, adrenal content of progesterone and cortisol, and in vitro production of progesterone and cortisol in adrenals, with or without synthetic ACTH in the incubate. At 35 days, three behavioural tests were made in succession ( n=72). In a Human test, the cub was held up by hand in a standardized way for 20 s. An Open-field test was followed by a Box test, where the cub placed in a small box and was allowed 30 s to enter the open field. The adrenals of prenatally stressed (PS) cubs weighed only 60% of those in the control group (C), while body weight was equal in PS and C cubs. The serum level of progesterone and the in vitro adrenal production of progesterone were higher in PS than C cubs. In PS females, the in vitro adrenal production of cortisol was higher than in C females. No significant effect of ACTH stimulation was found. In general, the effects on progesterone parallelled the effects on cortisol. These results indicate that prenatal stress may enhance the postnatal adrenocortical function. PS cubs remained more active during the human test, crossed more lines and entered more squares in the open field, and more frequently entered the open field in the box test. These results may indicate a higher behavioural reactivity in novel situations in prenatally stressed cubs. Whether the increased adrenocortical function and behavioural reactivity is related to reduced welfare remains to be determined. Further studies on the effects of prenatal stress in farm animals are recommended.