Gabriel Vieira Ramos

A Quarter Horse mare was presented with a history of imidocarb intoxication. During the initial evaluation, the patient presented an initial episode of syncope, in addition to a Grade III/IV diastolic murmur. On the basis of the observed condition, the animal underwent echocardiographic evaluation, in which artifacts were detected and subsequently characterized as air bubbles, restricted to the right cardiac chambers. A diagnosis of venous air embolism resulting from right jugular venocatheterization was made. This is the first reported case of venous air embolism secondary to jugular venocatheterization diagnosed by means of transthoracic echocardiography in a horse.

Maximal lactate steady state (MLSS) and its predictive thresholds, including the lactate threshold (LT), are widely used to estimate endurance capacity, prescribe training, and assess the effects of training. The human literature identified approximately twenty‐five methods to predict the MLSS. This communication compares the concordance between the two D _MAX methods and the MLSS. Under laboratory conditions, ten teaching horses underwent a submaximal graded exercise test (GXT) on a treadmill to obtain their lactate‐velocity curves (LVC). They performed three to five 30‐min continuous running sessions to determine the MLSS. The traditional D _MAX method was determined using the maximal distance from LVC to the line formed by its endpoints. A new calculated D _MAX method (D _MAXC ) involved mathematically determining the point that results in the maximum distance from a curve connecting the start to the endpoint of the LVC. The agreement among the velocities corresponding to the D _MAX (V _MAX ), D _MAXC (V _MAXC ), and the MLSS (V _MLSS ) was established using a Bland‐Altman plot and ordinary least products (OLP) analysis. The average lactatemia at V _MLSS , V _MAX , and V _MAXC was 1.50 ± 0.36 mM, 2.02 ± 0.66 mM, and 1.92 ± 0.65 mM, with respective speeds of 5.42 ± 0.57 m/s, 6.42 ± 0.71 m/s, and 6.35 ± 0.66 m/s. The mean difference between V _MAX ‐V _MLSS and V _MAXC ‐V _MLSS was ‐1.01 ± 0.61 and ‐0.93 ± 0.67 m/s, respectively. V _MAX and V _MAXC did not show constant and proportional biases compared to V _MLSS . In the GXT protocol used in this current study, D _MAX approaches appear to be accurate and reliable methods for lactate threshold determination and estimating MLSS in teaching horses.

Physical activity is recognized as a modulator of the intestinal microbial metabolism in humans and may also influence the microbiota of horses subjected to physical conditioning. While the physiological benefits of submaximal training are well-documented, its effects on the intestinal microbiota of horses that are fed a forage-only diet remain insufficiently understood. This study evaluated the fecal microbial composition of pasture-kept horses at three timepoints: before training (Submax), after seven weeks of exercise (Week7), and after 30 days of recovery (Trev30). Compositional analysis of the microbiota was explored by sequencing the V4 region of the 16S rRNA gene. A stable forage-only diet, confirmed by bromatological analysis, indicates the observed microbial shifts were primarily exercise-induced. Significant temporal dynamics in beta diversity (p = 0.001) indicated a marked shift in microbial community structure after training (Week7), with a subsequent partial restoration after recovery (Trev30). No significant changes in alpha diversity were detected (p > 0.05). A transient increase in the phylum Proteobacteria at Week7, which decreased by Trev30, suggested microbial adaptation to exercise-induced metabolic demands. LEfSe analysis identified the genera Rummeliibacillus (trained) and Hungateiclostridiaceae (controls) as discriminant between groups. Fecal pH showed a slight reduction after seven weeks, without statistical differences, and returned to equilibrium values in Trev30. Submaximal training induced a reversible modulation of the equine gut microbiota, demonstrating its adaptive capacity while maintaining overall ecological stability.

Exercise intolerance may be a primary symptom of myxomatous mitral valve disease (MMVD) and a significant factor in reducing the quality of a dog’s life. Aerobic training effectively improves oxygen uptake and life expectancy in human patients with chronic heart failure. Lactate threshold (LT) is used to prescribe training programs. We conducted a study with dogs diagnosed with asymptomatic MMVD (stage B1), using the velocity corresponding to the visual lactate threshold (VLTv) and an eight-week submaximal training program (STP), three times a week, with each session lasting 30 min, to improve their aerobic fitness. The dogs were assigned into two groups: a healthy control group and a MMVD group (stage B1). The treadmill-based graded exercise test (GXT) was used to determine the lactate-velocity curve (LVC) inflexion point. We utilised the velocity corresponding to 70% VLTv as the external load STP, representing a training zone between 145 and 157 bpm. Before the STP, VLTv and maximum velocity (Vmax) were lower in B1 dogs compared with the healthy group. The VLTv increased in the B1 dogs, resulting in rightward shifts of the LVC. The VLT values for healthy dogs were 3.62 ± 0.90 m/s and 4.75 ± 0.6 m/s; for B1 dogs were 3.03 ± 0.6 m/s and 3.8 ± 0.75 m/s in the pre-STP and post-STP. The Vmax values were 4.50 ± 0.70 m/s and 4.75 ± 1.04 m/s for healthy dogs, and 4.0 ± 0.53 m/s and 4.66 ± 0.74 m/s for B1 dogs. In both groups, changes in the relationship between lactatemia and exercise work may indicate improvements in aerobic and anaerobic capacities. VLTv, as an external training loading, should be considered when prescribing tailored training programs for dogs with asymptomatic myxomatous mitral valve disease to improve their muscular and cardiovascular function and exercise tolerance.

The effects of conditioning on cardiac function in young horses is still unknown. For this reason, this study evaluated the left ventricular (LV) function of young horses by echocardiography after six weeks of conditioning. Fourteen untrained young purebred Arabian horses were evaluated at rest and after a stress test (ST) before and after a six-week conditioning program. There was an increase in V₄ (p < 0.001) after conditioning, as well as a reduction in both heart rate (HR) at rest and peak HR during the ST (p < 0.001). There was also a reduction in internal diameter, along with an increase in interventricular septal, free wall and mean thicknesses and LV mass (p < 0.05). After the ST, the conditioned animals showed higher values of velocity time integral, stroke volume, systolic and cardiac indices, ejection (ET) and deceleration times (DT), end-diastolic volume, time to onset of radial myocardial velocity during early diastole and time to peak of transmitral flow velocity, in addition to reduced pre-ejection period (PEP), PEP/ET ratio and mean velocity of circumferential fiber shortening (p < 0.05). The conditioning protocol promoted physiological adaptations that indicate an improvement in the animals’ aerobic capacity associated with an enhanced left ventricular function.

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, pCO₂, HCO₃⁻, and electrolyte measurements. The LMS and strong ion difference (SID₄) 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), pCO₂ (from 42.95 ± 1.58 to 45.06 ± 0.81 mmHg), HCO₃⁻ (from 27.01 ± 1.02 to 28.91 ± 0.86 mmol/L), and SID₄ (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.