Determination of Myofiber Types of Mangalarga Mares and Their Hybrids

Abstract

IntroductionThere are no published studies that characterize the different myofiber types of Mangalarga (ML) horses and hybrids. This study aimed to characterize and compare muscle fibers of the gluteus medius of ML mares and young and inactive mules resulting from the breeding of these mares with a Brazilian donkey.MethodsPercutaneous biopsies were performed in 11 mares and their foals (10 mules), at a depth of 60 mm. Fiber types were determined by comparing identical images using both the staining techniques of myofibrillar adenosine triphosphatase (mATPase) and nicotinamide adenine dinucleotide‐tetrazolium reductase (NADH‐TR). Stains for mATPase were pre‐incubated in acid medium followed by alkaline incubation. The frequency (F%) and relative total area (RTA%) of fiber types I, IIA and IIX were analysed. The cross‐sectional area (CSA, μm2) was quantified by the NADH‐TR technique. The means were compared using ANOVA followed by Tukey test (P<0.05).ResultsThe frequency of type IIA fibers was greater than types I and IIX. Type IIX fibers had higher CSA than I and IIA. The RTA of type IIX fibers was greater than type IIA fibers followed by type I. The higher RTA value of IIX fibers resulted from higher CSA. There was no difference between the variables for mares compared to the mules.ConclusionsML mares and mules that resulted from breeding with the Brazilian donkey have a high prevalence of type IIA fibers in the gluteus medius. This fatigue‐resistant fiber uses both metabolic pathways, glycolytic and oxidative, to obtain energy during muscle contraction, thus giving the ML mares and mules good performance in horseback riding, marching contests and endurance rides.Ethical Animal ResearchAll procedures were approved by the institutional animal care and use committee of the university (CEUA, Process: 01370/12). Sources of funding: Fundação de Amparo a Pesquisa do Estado de São Paulo. Process: 04655‐9/2012. Competing interests: none.