• A R Hollis, R C Boston, and K T T Corley.
• New Bolton Center, 382 West Street Road, Kennett Square, PA 19348, USA.
• Equine Vet. J. 2008 Jan 1; 40 (1): 64-9.

Reason For Performing StudyNeonatal foals succumb rapidly to hypovolaemic shock in comparison to mature horses; they do not consistently increase their heart rate in response to hypotension and respond differently to fluid administration. The hormonal responses to hypovolaemia in the horse and foal require investigation.HypothesisThe hormonal responses to hypovolaemia and fluid administration differ between mature and neonatal horses.MethodsFive mature horses and 5 neonatal foals fulfilling predetermined criteria for hypovolaemia, were included in the study. A blood sample was taken at admission and after normalisation of fluid balance. These were analysed for plasma aldosterone, vasopressin (AVP) and atrial natriuretic peptide (ANP). Normally distributed variables were compared using the Student's t test and nonparametric data using the Mann-Whitney U test.ResultsANP, AVP and aldosterone were higher before fluid resuscitation than after fluid resuscitation in mature horses. Aldosterone was higher before than after fluid resuscitation in foals, and was higher in foals both before and after fluid resuscitation than in mature horses. ANP was lower in mature horses after fluid resuscitation than in foals. No other comparisons were significantly different.ConclusionsThe hormonal responses of the mature and neonatal horses are different during hypovolaemia and following fluid resuscitation.Potential RelevanceThe differences in the hormonal responses to hypovolaemia and fluid resuscitation may be important when considering fluid resuscitation of hypovolaemic horses and foals, and warrants further investigation.

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