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Cyclical plasma electrolyte and acid–base responses to meal feeding in horses over a 24-h period

Published online by Cambridge University Press:  09 March 2007

Amanda Waller ,
Kerri Jo Smithurst ,
Gayle L Ecker ,
Ray Geor  and
Michael I Lindinger
Amanda Waller*
Affiliation:
Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1
Kerri Jo Smithurst
Affiliation:
Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1
Gayle L Ecker
Affiliation:
Equine Centre, University of Guelph, Guelph, ON, Canada N1G 2W1
Ray Geor
Affiliation:
Department of Biomedical Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1
Michael I Lindinger
Affiliation:
Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1
*
*awaller@uoguelph.ca
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Abstract

The present study used the physicochemical approach to characterize the changes in plasma electrolyte and acid–base states that occur in horses in response to feeding. Jugular venous blood was sampled every 0.5–2 h over a 24-h period from two groups (n = 4 and n = 5) of Standardbreds fed a mixed hay and grain ration at 8 am and 7 pm. One group of horses was studied in October, and one in December. The time course and magnitude of feeding responses differed between groups, and between the morning and evening meals. Feeding-induced changes in plasma electrolyte and acid–base variables occurred rapidly, within the first 1–3 h of meal consumption. The plasma acidosis associated with eating the meal was marked by increased plasma [H+] and decreased TCO2. The primary contributors to the increases in plasma [H+] were the decrease in the plasma concentration of strong ions ([SID]) and the pCO2. The increase in plasma total weak acid (protein) concentration ([Atot]) post-feeding had only a minor effect on the acid–base state. The feeding-induced acidosis abated 3–6 h after the meal, showing cyclical recovery of physicochemical variables that contributed to the acid–base disturbance. It is concluded that several key plasma electrolyte and acid–base parameters undergo significant, cyclical fluctuations in response to feeding in horses.

Keywords

equinepHH+physicochemical approachnutrition
Type
Research Article
Information
Equine and Comparative Exercise Physiology , Volume 2 , Issue 3 , August 2005 , pp. 159 - 169
Copyright
Copyright © Cambridge University Press 2005

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