Acid‐Base Imbalances in Endurance Racing Using Traditional and Quantitative Approaches

Abstract

IntroductionAcid‐base disturbances are frequently assessed using traditional variables PCO2, pH, and bicarbonate. This study aimed to compare the changes in acid‐base balance in horses performing a CEI endurance race (160 km) using traditional and quantitative methodologies.MethodsBlood samples were drawn before racing, at the vet‐gate (66 km), immediately after racing, and 2 and 15 h after racing from 18 participating horses. The mean velocity of the horses was 17 km/h. PCO2 and pH were measured (I‐Stat). Strong ion difference (SID), anion gap (AG), strong ion gap (SIG) and total volatile buffers (Atot) were calculated using formulas from the literature. Data for finishers (F) and non‐finishers (N) was compared with an unpaired test. Data collected for finishers at all time‐points was compared by repeated ANOVA followed by Tukey's test.ResultsPCO2 was lower in group N at the 66 km time‐point. In group F, AG had a bimodal behaviour, declining immediately after exercise and then increasing at 2 and 15 hours. There was a slight increase in pH post‐exercise. After 2 hours, Atot increased while PCO2 decreased. Compared to SIG immediately after racing, SIG at 2 and 15 hours after racing was decreased. Traditional methodology suggested mild respiratory and metabolic alkalosis, possibly due to hyperventilation of the finishers. Quantitative methodology suggested metabolic acidosis reflected by decreasing SID trend and a significant increase of Atot.ConclusionsAcid‐base imbalances are present in endurance racing horses and differences were found between the traditional and quantitative methods of assessment.Ethical Animal ResearchAll procedures were approved by the institutional animal care and use committee of the university (CEUA, Process: 007347/13). Explicit owner informed consent for participation in this study is not stated. Sources of funding: FAPESP ‐ Fundação de Amparo à Pesquisa do Estado de São Paulo (Process 2013/00449‐8). Competing interests: none.