Neonatal handling permanently alters hypothalamic-pituitary- adrenal axis function, behaviour, and body weight in boars

Abstract

Neonatal handling permanently alters hypothalamicpituitary-adrenal axis (HPA) function in rats. In the rat, this treatment increases hippocampal glucocorticoid receptors (GR) and dampens plasma ACTH and corticosterone responses to stressors. The objectives of this study were to determine whether neonatal handling of pigs would effect permanent changes in plasma corticosteroid binding capacity (CBG), basal or stressor-induced plasma cortisol and ACTH concentrations, brain or pituitary GR levels, dexamethasone suppression of plasma cortisol and ACTH concentrations, behaviour in an open field-test pen, and body weights. Twelve litters of pigs were randomly assigned to either neonatal handling or no disturbance. Handled litters were removed from the farrowing crate for 10 min per day for the first 14 days of life. Male pigs were kept for the study and the boars were weighed monthly. At 7 months of age, boars were tested for locomotory behaviour in an open field-test pen. The boars were implanted with indwelling ear-vein catheters and blood samples were obtained basally, during and after application of a nose snare, and after 0·04 mg/kg dexamethasone. Boars were killed and blood samples were obtained and the brain and pituitary glands collected. Handled boars had greater (P<0·05) plasma CBG binding and lower basal total (P<0·05) and calculated free (P<0·03) plasma cortisol concentrations. No significant differences between treatments were found in plasma ACTH or cortisol responses to a nose-snare stressor; however, when killed, handled boars had greater (P<0·02) plasma ACTH concentrations. Handled and non-handled boars did not differ in plasma ACTH or cortisol responses to dexamethasone. There was no treatment effect on GR expression in the pituitary gland, frontal cortex, hippocampus, or hypothalamus. Behaviourally, the handled boars had higher (P<0·03) locomotor scores over inner squares and a lower (P<0·05) ratio of outer:inner squares entered in open field-tests. During the first 7 months of life, body weights were lower (P<0·004) for handled boars. In conclusion, neonatal handling permanently altered HPA function in pigs, but in a manner dissimilar to that found in the rat. These changes induced in the pig were not beneficial for commercial production with respect to body weight.

Pre-natal social stress and post-natal pain affect the developing pig reproductive axis

“…The observation that tail-amputated male pigs had fewer proliferating Leydig cells, smaller testes and lower E 2 concentrations suggests that testicular growth and development were compromised. As both the amputated and intact groups were handled in the same way and were of equivalent weight at slaughter, the results do not appear to be a consequence of the handling stress described by Weaver et al (2000) or of altered feed intake. However, work by Klemcke et al (1995) showing that neonatal (12 days of age) boars had increased ACTH and cortisol responses on the day after being restrained for 1 min highlights the extreme sensitivity of neonatal pigs to a modest stressor.…”

“…In addition, piglet's tails are often removed within a few days of life as a means to prevent later tail biting; a procedure which causes an acute stress response (Sutherland et al 2008) and behaviour indicative of pain perception (Rutherford et al 2009). Although there are apparently no reports of the effects of early post-natal pain or trauma on subsequent reproductive function, it is known that male pigs that were handled daily for the first 2 weeks of life had altered hypothalamic-pituitaryadrenal (HPA) function when assessed at 7 months of age (Weaver et al 2000).…”

Interactions between Nitric Oxide and Corticosterone in the Regulation of Progenitor Cell Proliferation in the Dentate Gyrus of the Adult Rat

“…Glucocorticoids show a marked, but variable, diurnal rhythm, and are moderated by stress as well as genetic factors, age, and 'programming' of adrenal function by early adversity (Dallman et al, 2004;Fish et al, 2004;Meaney et al, 1996;Mirescu et al, 2004;Sapolsky et al, 1987;Weaver et al, 2000).…”

Environmental enrichment in early life affects cortisol patterns in growing pigs

“…De Jonge et al (1996) showed that in subordinate pigs, environmental conditions in the first 6 weeks of life affected the expression of several symptoms of social stress later on. Weaver et al (2000) and Kanitz et al (2004) reported effects on later stress physiology of early adverse experience in the form of short-time social isolation during the first 11 to 14 days of life.…”