Background The expressions of vitamin D receptor (VDR) and vitamin D‐metabolising enzymes (CYP27B1 and CYP24A1) in skeletal muscle have been reported. However, the regulation of this vitamin D system in horse skeletal muscle after high‐intensity exercise has not yet been elucidated. Objectives To investigate the effect of high‐intensity exercise on the expression of vitamin D system‐related proteins in horse skeletal muscle and its associations with skeletal muscle stem cell (SMSC) activity and serum 25(OH)D level. Study design Longitudinal study. Methods Six healthy ponies (5 geldings, 1 mare; age 6.3 ± 2.2 years) were studied. Serum and muscle samples were taken from the jugular vein and gluteus medius respectively. Samples were collected at pre‐exercise, post‐exercise, 1 and 3 weeks after a single bout of high‐intensity exercise. Protein expression levels of VDR, CYP27B1, CYP24A1, OxPhos and Pax7 (SMSC marker) were determined using immunohistochemical analysis. Oxidative capacity and intramuscular glycogen content were evaluated using histochemical analysis. Blood biochemistry was analysed for lactate concentration and creatine kinase (CK), and 25(OH)D activity. Results High‐intensity exercise significantly upregulated Pax7 and VDR protein expression, which correlated with significantly increased blood lactate and serum CK levels immediately post‐exercise. Serum 25(OH)D2 level correlated with CYP27B1 protein expression in skeletal muscle, and it reduced significantly immediately post‐exercise and at 1 and 3 weeks post‐exercise. However, CYP24A1 protein expression was unchanged throughout study periods. Main limitation The healthy ponies could not represent a fit population of racehorses and eventers. Conclusions The rapid increase in Pax7 and VDR protein expression along with serum CK level after high‐intensity exercise demonstrated an association between SMSC activity and activation of the vitamin D system in response to muscle injury in horses. Moreover, a decrease in CYP27B1 protein expression, correlated with a reduction in serum 25(OH)D2, may indicate a compromised vitamin D metabolism after high‐intensity exercise.

BackgroundThe match play patterns in equestrian polo are unique and require specific training programs to ensure sport performance. The effect of commonly used exercise training regimens on the adaptation of skeletal muscle is unclear. The present study investigated the modulating effects of the classic training regimen, comprised of aerobic exercise training with increasing exercise intensities and varying duration combined with match play, on the properties of muscle in polo ponies. Nine healthy adult female polo ponies were subjected to four consecutive subsets of 1 year classic training regimen including basal activity (B), low intensity (L), low to moderate intensity (LM), and low to moderate intensity training plus match play during polo tournament (LMP), respectively. At the end of each training period, gluteus medius muscle samples were taken for determination of muscle fiber type distribution, muscle metabolic capacity, capillary density, and lipid and glycogen content. The expression profile of metabolic genes including succinate dehydrogenase (SDH), phosphofructokinase (PFK), glycogen phosphorylase (PYG), and glycogen synthase (GYS) were also measured.ResultsAmong all exercise training subsets, only LMP exercise period caused an increase in the number of oxidative fibers (type IIa), along with increases in properties related to oxidative metabolism including high capillary density, intramuscular lipid content, and expression of SDH and PYG genes, with a corresponding decrease in the number of type IIx muscle fibers.ConclusionThe combination of low to moderate and high intensity training in LMP are only sufficient to induce changes in oxidative characteristics. As the first scientific evidence providing such insight about the classic polo training regimen, the data forms a basis for further consideration in training program design.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0874-6) contains supplementary material, which is available to authorized users.

Krungthongpatthana (2020) The effect of the z-bar shoeing method on surface dimension of the hoof wall and time required for therapeutic shoeing in three horses with a sheared heel,

Navicular syndrome causes chronic lameness and attenuates the exercise performance. Several shoeing methods have been implemented, but their success has been inconsistent. The objective of this study was to develop a diagnostic aid to select the appropriate shoeing method for the treatment of navicular syndrome. Five equestrian horses with chronic lameness were studied. The lameness examination, then unilateral anaesthetics and trotting after each point of administration were performed until no lameness sign. Radiographs were later taken of the affected hooves. The horses were diagnosed with navicular syndrome with unilateral palmar pain, z bar shoes were applied on the lame legs. Gait was analysed before shoeing and 5 min, 2, 4 and 8 weeks after shoeing except for horse no. 3, for which the evaluation at 8 weeks was omitted. Horses no. 2 and 3 showed a significant decrease in lameness score at 2 weeks and progressive decrease at 4 or 8 weeks. Horses no. 1, 4 and 5 demonstrated a significant reduction in lameness score at 4 weeks and substantial decreases at 8 weeks after shoeing. Although a limited number of animals, unilateral perineural anaesthesia on the lame leg facilitates the selection of z bar shoeing for navicular syndrome treatment.

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