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Mangalarga Marchador (MM) is the most important and numerous equine breed in Brazil. So far, no studies have been carried out on the breed's skeletal muscle composition, which is important to develop specific physical conditioning programs. To characterize the skeletal muscle fiber composition of young MM females, gluteus medius muscle biopsies were obtained from 13 fillies between 2.5-and 3-year-old using a biopsy needle at 60-mm depth. Types I, IIA, and IIX fibers were determined by the metachromatic staining method of ATPase activity in myofibers using preincubation followed by incubation in alkaline medium. Relative frequency (%F), average cross-sectional area (CSA), and relative crosssectional area (%CSA) of each muscle fiber type were determined. Considering %F, 29.5 AE 5.4% were type I, 40.3 AE 5.5% were type IIA, and 30.2 AE 5.9% were type IIX fibers. CSA of type I fibers was 2,633 AE 798 mm 2 , of type IIA was 3,407 AE 492 mm 2 , and of type IIX was 5,856 AE 1,237 mm 2 . %CSA was composed of 19.7 AE 4.9% of type I fibers, 35.4 AE 4.7% of type IIA, and 44.9 AE 7.4% of type IIX. The gluteus medius muscle of untrained MM fillies was predominantly composed of type IIA fibers, but the highest total relative area was occupied by type IIX fibers, suggesting moderate aptitude to the oxidative and glycolytic metabolisms.

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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...