Milk cortisol concentrations as an indicator of stress in lactating dairy cows

G.A. Verkerk, A.M. Phipps and L.R. Matthews

Animal Behaviour and Welfare Research Centre, AgResearch, Ruakura AgCentre, Private Bag 3123, Hamilton, New Zealand.

Proceedings of the New Zealand Society of Animal Production, 1996, 56: 77-79

The aim of this study was to compare cortisol concentrations in plasma (PCC) and milk (MCC) following administration of exogenous ACTH1-24 or activation of the hypothalamo-pituitary-adrenal axis by a stressor (transport) in cows. Fifteen cows in mid-lactation were assigned to treatments with ACTH1-24 (0.05 mg Synacthenô iv at 1300h), transport (trucking for two 45 min periods from 1300h) or control (sampling only) in a 3x3 Latin square design. Blood samples were collected hourly from 1300- 1500h and a composite milk sample was obtained at routine milking at 1515h.

There was a 6-fold elevation in PCC by 60 min following both ACTH treatment and transportation. At 120 min, PCC was two-fold higher in ACTH treated cows but remained at levels similar to those at 60 min in the transported animals, indicating that the adrenocortical response had been maintained during transport. Mean MCC was 12-fold greater after the transport treatment and a factor of 2 higher after ACTH treatment, compared to the control treatment (P<0.01). Values of MCC and PCC at the 120 min sampling were highly correlated (r = 0.80; P<0.001). This suggested that MCC may be a useful indicator of adrenocortical response to stressors, provided samples are obtained during the period of elevated PCC.

Keywords: NZSAPAB; Plasma cortisol; milk cortisol; ACTH, transport; dairy cattle.

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Last Updated 18-03-1997