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Factors contributing to plasma TCO 2 and acid‐base state in Ontario Standardbred racehorses
Author(s) -
WALLER A. P.,
PEARSON W.,
LINDINGER M. I.
Publication year - 2010
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.2010.00249.x
Subject(s) - zoology , horse , anion gap , medicine , chemistry , biology , paleontology , acidosis
Summary Reasons for performing study: Standardbred and Thoroughbred racehorses around the world are tested for performance enhancing substances. Among these are blood alkalising substances that raise plasma pH and total carbon dioxide (TCO 2 ) concentration. However, many horses have an elevated TCO 2 due to dietary, environmental and health concerns without having been administered an alkalising substance. Objectives: The purposes of this study were to determine the acid‐base profile of a cross section of Standardbred horses in racing/race training in Ontario and the main independent variables that contributed to acid‐base state. Materials and methods: On nonracing days, blood from 211 horses at rest, from 9 training facilities, was analysed within 30 min for plasma pH (7.406 ± 0.039; mean ± s.e.), PCO 2 (50.0 ± 3.4 mmHg), from which [HCO 3 ‐ ] (31.2 ± 2.8 mmol/l) and [TCO 2 ] (33.1 ± 2.9 mmol/l; range 25.66–42.9) were calculated. From these, a subset of 161 horses had full data sets for plasma protein and strong ion concentrations. These data were further analysed by facility and level of TCO 2 . Data on nutrition, training, racing and medications were also collected. Results: There were significant differences amongst facilities with respect to plasma pH, TCO 2 , strong ion difference ([SID]), PCO 2 and total weak acid concentration ([A tot ]). Horses having the highest TCO 2 (37.0–42.9 mmol/l, n = 16) had significantly higher [SID] (52.9 ± 0.8 mEq/l) and PCO 2 (52.5 ± 0.7 mmHg) and relatively low [A tot ] (14.9 ± 0.7 mEq/l) compared to average TCO 2 (32.1.0–34.9 mmol/l) horses (n = 75). In horses with the lowest TCO 2 (n = 11) the greatest contributor was elevated [A tot ] (21.0 ± 0.7 mEq/l) and unmeasured (acetate, citrate, proprionate, butyrate) weak acids (7.0 ± 0.2 mEq/l) while [SID] (49.6 ± 0.8 mEq/l) and PCO 2 (47.8 ± 1.0 mmHg) were similar to average TCO 2 horses. Thirty‐two horses had a TCO 2 ranging from 35.0–36.9 mmol/l). Conclusions: There is a wide range of acid‐base state and factors contributing to acid‐base state amongst Standardbred race horses in Ontario. Dietary, environmental and handling practices and health concerns, that elevate plasma [SID], lower [A tot ] and lower the concentration of unmeasured weak acids are the primary contributors to alkalosis and elevated TCO 2 .