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

Neonatal handling permanently alters hypothalamic-pituitary-adrenal axis (H PA) function in rats. In the rat, this treatment increases hippocampal gluc ocorticoid receptors (GR) and dampens plasma ACTH and corticosterone respon ses to stressors. The objectives of this study were to determine whether ne onatal handling of pigs would effect permanent changes in plasma corticoste roid binding capacity (CBG), basal or stresser-induced plasma cortisol and ACTH concentrations, brain or pituitary GR levels, dexamethasone suppressio n of plasma cortisol and ACTH concentrations, behaviour in an open field-te st pen, and body weights. Twelve litters of pigs were randomly assigned to either neonatal handling or no disturbance. Handled litters were removed fr om the farrowing crate for 10 min per day for the first 14 days of life. Ma le pigs were kept for the study and the boars were weighed monthly. At 7 mo nths of age, boars were tested for locomotory behaviour in an open field-te st pen. The boars were implanted with indwelling ear-vein catheters and blo od samples were obtained basally, during and after application of a nose sn are, and after 0.04 mg/kg dexamethasone. Boars were killed and blood sample s 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 di fferences between treatments were found in plasma ACTH or cortisol response s 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 n o 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 mann er dissimilar to that found in the rat. These changes induced in the pig we re not beneficial for commercial production with respect to body weight.