Effect of Lactate Minimum Speed-Guided Training on the Fluid, Electrolyte and Acid-Base Status of Horses

SIMPLE SUMMARY: Horses are susceptible to metabolic disturbances provoked by dehydration and electrolyte and acid-base imbalances that can affect their welfare and result in their elimination from competitions. The conditioning guided by physiologic variables such as lactate can bring greater gains in terms of conditioning, and therefore better body preparation for the exercise challenge. In this study, horses were submitted to a lactate minimum speed (LMS)-guided training program for six weeks, and its effect on their water, electrolyte, and acid-base statuses was measured. Even though it was found that this training method has a positive impact on the horses’ acid-base status during exercise, the protocol needs adaptation in order to maximize their fitness gain. ABSTRACT: The effect of lactate minimum speed (LMS)-guided training on horses’ homeostasis is still unknown. Thus, this study aimed to evaluate the effect of an LMS-guided training program on the fluid, electrolyte and acid-base status of horses. Ten untrained Arabian horses were submitted to an LMS test on a treadmill before and after six weeks of training. The training intensity was 80% of the LMS in the first three sessions and 100% of the LMS in the other sessions. The venous blood was collected before (T-1) and after (T-2) training at rest, during and after the LMS test for lactate, pH, pCO(2), HCO(3)(−), and electrolyte measurements. The LMS and strong ion difference (SID(4)) were calculated. A mild increase in the mean values (p > 0.05) was observed at rest in T-2 in comparison with T-1 in the following variables: pH (from 7.436 ± 0.013 to 7.460 ± 0.012), pCO(2) (from 42.95 ± 1.58 to 45.06 ± 0.81 mmHg), HCO(3)(−) (from 27.01 ± 1.02 to 28.91 ± 0.86 mmol/L), and SID(4) (from 33.42 ± 1.45 to 35.06 ± 2.94 mmol/L). During T-2, these variables were more stable than during T-1. Despite the improvement in fitness, the LMS did not indicate a significant difference (from 5.40 ± 0.55 to 5.52 ± 0.20 m/s). The results confirmed that the LMS-guided training program had a positive impact on the horses’ acid-base status, although some adaptations are still required to improve their fitness.