Evolution of Echocardiographic Dimensions with Age and Training in Young Endurance Horses

Abstract

This publication is a compilation of all Research Abstracts presented at the Ninth International Conference on Equine Exercise Physiology. Unlike previous ICEEP conferences there will not be a conference proceedings of full length manuscripts. These abstracts succinctly summarise a wide array of investigations relevant to the equine athlete, and will be useful to veterinarians and others involved in management of horses used for sport, work and competition. The abstracts encompass the topics of Applied Physiology; Biochemistry, Haematology, Endocrinology, and Thermoregulation; Cardiovascular and Respiratory; Muscle and Bone; Nutrition; Genomics, Proteomics, and Metabolomics; Biomechanics and Locomotion; as well as Physiotherapy, Rehabilitation, and Equitation science.The International Committee of ICEEP publishes these abstracts so that the most recent scientific information is available to a wide audience, including veterinarians, physiotherapists, trainers, owners and riders.The Introduction:The ability to accurately assess equine oxygen consumption (VO2) under field conditions has been limited by the need for unrestricted gas exchange.Methods: Two variations of a mask and an associated electronics control module (ECM) were designed to enable breath-by-breath measurement of airflows with two 8.0 cm diameter pneumotachometers located 7.5 cm in front of each narus and connected to differential pressure transducers mounted on the outside of the mask. The ECM was comprised of electronics for signal filtering to the flow transducers, an oxygen sensing cell, and an analog-to-digital converter all powered by a lithium-ion battery. The battery also 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. VO2 was determined from these recordings by an operator using a customized software analysis program. One mask encased the lower head (E). The other left the jaw free so horse could wear a bit and be ridden (R). Multiple treadmill exercise tests were undertaken by 6 horses to measure VO2max and blood gases. Each mask was worn twice and results compared to those from an open flow-through system (O) by 2-way RMANOVA (P<0.05). Utility of the system was evaluated using the intraclass correlation coefficient of 4 independent raters.Results: Blood gases and VO2max (152.0 ± 4.0 (mean ± SEM; O), 147.7 ± 4.3 (E), 150.7 ± 3.3 (R) ml/(kg.min) were not different between masks. VO2 measures were reproducible for each mask. Agreement between the 4 raters was excellent (intraclass correlation coefficient = 0.99). Conclusions:Masks capable of measuring VO2 during field exercise were developed, tested and found accurate by multiple users.Ethical Animal Research: Studies performed were approved by the Institution's Animal Care and Use Committee (protocol #3807). Sources of funding: Institutional sources. Competing interests: Washington State University has filed notice of i...

Effects of Age, Exercise Duration, and Test Conditions on Heart Rate Variability in Young Endurance Horses

“…Firstly, the HR was higher in 4-year-olds than in 5- and 6-year-olds during the first 15 min of cantering; secondly, the HR was higher in 5-year-olds than in 6-year-olds during a 30-min canter. In a study of endurance horses, Trachsel et al ( 2014 ) showed that heart size and stroke volume increased between the ages of 4 and 6. As the cantering speed during the exercise test was steady (22 km.h −1 , Figure 3 ), for a given cardiac output, a higher stroke volume may explain a lower HR in the older horses.…”

“…For instance, Seeherman and Morris ( 1991 ) showed that the maximum HR (HR max ) did not change with age in yearling vs. adult Thoroughbred horses, whereas aerobic power and exercise capacity increased with age and training. When considering cardiac autonomic control and given that left ventricular volume and stroke volume are greater in 6-year-old endurance horses than in 4-year-olds (Trachsel et al, 2014 ) for the same cardiac output, HR should be lower in 6-year-olds than in 4-year-olds. These changes probably mean that HRV differs in 4- vs. 6-year-olds.…”