Cardiac vagal tone, plasma cortisol, and dehydroepiandrosterone response to an ACTH challenge in lame and nonlame dairy cows

Jurkovich, Viktor and Bakony, Mikolt and Laky, Enikő and Ruff, Ferenc and Kézér, Fruzsina Luca and Bende, Andrea and Kovács, Levente (2019) Cardiac vagal tone, plasma cortisol, and dehydroepiandrosterone response to an ACTH challenge in lame and nonlame dairy cows. DOMESTIC ANIMAL ENDOCRINOLOGY. ISSN 0739-7240 (In Press)

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Abstract

We studied the adrenocortical and vagal tone response to a single ACTH challenge in lame (n = 9) vs nonlame (n = 9) cows. Cows were paired according to parity, days in milk, and milk yield. Plasma cortisol and dehydroepiandrosterone concentrations and cardiac vagal tone response (high-frequency component of heart rate variability) were compared after intravenous ACTH administration. Baseline, minimum/maximum, amplitude of the response and area under the response curve were compared. No difference could be detected between groups in the cortisol response. Dehydroepiandrosterone was irresponsive to ACTH treatment, and concentrations did not differ between lame and nonlame cows. Vagal tone decreased in response to the ACTH treatment. High frequency was lower in the lame group at all sampling times. Lameness was associated with delayed return to baseline. We concluded that the adrenal response capacity is not influenced by lameness, which supports the concept of lameness being a chronic intermittent rather than a chronically persistent stressor. Dehydroepiandrosterone concentrations were not proven to be useful indicators of hypothalamus–pituitary axis dysfunction in cattle. A decreased vagal contribution to heart rate variability—possibly coupled with increased sympathetic modulation—was observed in lame cows, which suggests that lameness affects the mechanisms underlying the action of ACTH on cardiovascular activity.

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