K. F. Gough

Serial evaluation of resting and exercising overground endoscopic examination results in young Thoroughbreds with no treatment intervention

BACKGROUND We hypothesised that grade/appearance for upper respiratory tract (URT) disorders identified at the first overground endoscopy (OGE) examination would vary at subsequent examinations. OBJECTIVES To compare OGE examinations from horses evaluated on at least two occasions under similar exercise conditions without treatment intervention. STUDY DESIGN Retrospective cohort. METHODS Pre-exercise and exercising OGE recordings from Thoroughbred horses undergoing multiple examinations under similar exercise conditions were reviewed, with the first two recordings for each horse statistically evaluated. Paired Wilcoxon signed-rank tests were used to assess differences in exercise and physiological parameters between examinations. Z-tests were used to assess the proportion of changes in URT disorder grade/appearance between examinations. A McNemars test was used to compare the proportion of horses with each disorder at each examination. Test-retest reliability across examinations was assessed using Spearmans ρ, and ordered logistic regression used to explore temporal effects on repeatability. Lattice plots were constructed to view variability in disorders over time. RESULTS Seventy-eight horses (median age 2.4 years) with 195 resting endoscopic examinations including 72/78 horses with 179 pre-exercise and exercising OGE examinations were evaluated. Median time between examinations was 226.5 days with no differences between exercise and physiological parameters. Grades significantly varied between examinations for all disorders, and in particular for palatal instability (PI) and epiglottic grade at rest. A temporal link between examination interval and disorder grade change was identified for PI and resting arytenoid asymmetry. MAIN LIMITATIONS OGE re-examinations within a shorter, more consistent time-frame would allow determination of intrahorse variability. The sample size was inadequate to conclusively establish temporal links between disorders and time between examinations. CONCLUSIONS Variability for most URT abnormalities identified with OGE should be considered when making therapeutic decisions based on a single examination and may partially explain development of additional URT conditions after surgical intervention. The Summary is available in Portuguese - see Supporting Information.

Validation of masks for determination of V̇O2max in horses exercising at high intensity

BACKGROUND The need for a horse to be ridden while wearing a measurement device that allows unrestricted ventilation and gas exchange has hampered accurate measurement of its maximal oxygen consumption (V̇O2 max) under field conditions. OBJECTIVES Design and validate a facemask with the potential to measure V̇O2 max accurately in the field. STUDY DESIGN Experiment with 6 × 6 Latin square design. METHODS Two variations of a mask and associated electronic control module (ECM) were designed to enable breath-by-breath measurement of airflows through two 7.8 cm diameter pneumotachometers located 7.5 cm in front of each narus. The ECM was comprised of an analogue-to-digital converter and a lithium-ion battery that provided power and signal filtering to the pneumotachometers and an oxygen sensing cell, and powered a pump connected to gas sampling ports between the nares and pneumotachometers. Airflow and oxygen content of inspired and expired gases were recorded through the ECM and electronically transferred to a notebook. V̇O2 was determined from these recordings using a customised software program. Mask B encased the lower jaw. Mask R left the jaw free so the horse could wear a bit if ridden. V̇O2 max and arterial blood gases were measured in 6 horses during multiple treadmill tests. Each mask was worn twice and results compared to those from an established open flow-through system (O) by ANOVA-RM (P<0.05). System utility was evaluated using the intraclass correlation coefficient of 4 independent raters. RESULTS Blood gases and V̇O2 max (151.9±7.0 [mean±s.d.; O], 151.5±9.6 [B], 149.5±7.5 [R] ml/[kg.min]) were not different between masks. V̇O2 max measures were reproducible for each mask. Intraclass correlation coefficient between raters = 0.99. MAIN LIMITATIONS Some rebreathing of expired air from mask dead space. CONCLUSION Masks capable of measuring V̇O2 max during treadmill exercise were developed, tested and found to be accurate. Mask R has potential application to measurement of V̇O2 max under field conditions.

Effect of Submaximal and High-Intensity Training on Venous Hemoglobin Concentrations in Thoroughbred Racehorses

Abstract This study examined the effect of submaximal and high‐intensity (sprint) training on venous hemoglobin concentration ([Hb]) in Thoroughbred (Tb) racehorses before and after high‐intensity exercise on the gallops. Measurements for n = 14 Tb yearlings took place during high‐intensity exercise on an all‐weather gallop during their breaking period before entering submaximal training (UT1) and then again as 2‐year‐olds before (UT2) and after sprint training (T). Weather, gallop conditions, peak heart rate (HR), peak velocity (Vpeak), and exercise distance were recorded and whole‐blood jugular venous samples taken before (T0) and 5 minutes after (T5min) exercise ended for packed cell volume (PCV), [Hb], and plasma lactate concentration ([LA]) measurements. Submaximal and sprint training duration including the number of sprint training sessions were recorded for each horse and included in the analyses. Data were analyzed using repeated measures analysis of variance followed by a Bonferroni t test and Pearson correlation; significance was P ≤ .05. Environmental temperature was significantly higher with firmer footing for T versus UT1 test days, with Vpeak significantly greater for T versus UT1 horses (P = .005). T5min PCV, [Hb], and [LA] were significantly higher than T0 (P < .0001) for all training stages, with no training effects observed. Vpeak was positively correlated with duration of submaximal training (r = 0.5, P = .0009) and the number of sprint training sessions (r = 0.4, P = .005), but there were no correlations between [Hb], training, and other physiological variables. These results suggest that improvement in Vpeak is related to training duration and intensity, and is influenced by the going, but is not affected by [Hb]. HighlightsEnvironmental temperature was higher with firmer footing for trained test days.Vpeak was significantly greater for trained versus untrained horses and positively correlated with training duration and intensity.Postexercise hemoglobins were higher than pre‐exercise at all training stages.Hemoglobin was not correlated with training or other physiological variables.Vpeak is affected by training duration and intensity, but not by hemoglobin.