Acute cortisol and behavior of dairy goat kids administered local anesthesia, topical anesthesia or systemic analgesia prior to cautery disbudding

Animals respond to stress by activating a wide array of behavioral and physiological responses that are collectively referred to as the stress response. Corticotropin-releasing factor (CRF) plays a central role in the stress response by regulating the hypothalamic-pituitary-adrenal (HPA) axis. In response to stress, CRF initiates a cascade of events that culminate in the release of glucocorticoids from the adrenal cortex. As a result of the great number of physiological and behavioral effects exerted by glucocorticoids, several mechanisms have evolved to control HPA axis activation and integrate the stress response. Glucocorticoid feedback inhibition plays a prominent role in regulating the magnitude and duration of glucocorticoid release. In addition to glucocorticoid feedback, the HPA axis is regulated at the level of the hypothalamus by a diverse group of afferent projections from limbic, mid-brain, and brain stem nuclei. The stress response is also mediated in part by brain stem noradrenergic neurons, sympathetic andrenornedullary circuits, and parasympathetic systems. In summary, the aim of this review is to discuss the role of the HPA axis in the integration of adaptive responses to stress. We also identify and briefly describe the major neuronal and endocrine systems that contribute to the regulation of the HPA axis and the maintenance of homeostasis in the face of aversive stimuli.

Dehorning and disbudding are routine painful procedures carried out on cattle to facilitate management. The pain caused by these procedures and its alleviation may be evaluated by monitoring behaviour and physiological responses, and by measuring their effects on weight gain. The cortisol response to cautery disbudding is significantly smaller than that to amputation dehorning which infers that the latter is more painful. Amputation dehorning stimulates a defined cortisol response with a rapid rise to a peak value within 30 min followed by a decline to a plateau which then declines to pre-treatment values after about 8 h. A cornual nerve blockade using lignocaine virtually eliminates the escape behaviour seen during disbudding and dehorning and reduces the plasma cortisol response to dehorning for about 2 h. Thereafter there is an increase in the plasma cortisol concentration, a delayed response, which lasts for about 6 h. A cornual nerve blockade, using lignocaine combined with cauterizing the wound caused by amputation dehorning, virtually eliminates the cortisol response as does combining a lignocaine blockade with the non-steroidal anti-inflammatory drug (NSAID) ketoprofen. When xylazine is combined with a cornual nerve blockade using lignocaine before dehorning, the cortisol response is virtually eliminated for about 3 h. When this regime is used before cautery disbudding and includes a NSAID given before and after disbudding the behaviour of calves so treated suggests that pain may be alleviated for 24 h. Cautery disbudding is preferable to amputation dehorning, but for optimal pain relief xylazine sedation, local anaesthesia and a NSAID should be used with both procedures.