Quarter Horses Research Articles

Ontario Racehorse Death Registry, 2003-2015: Descriptive analysis and rates of mortality.

The Province of Ontario maintains a registry of racehorse deaths occurring within 60days of a race or trial entry that provides insight into mortality rates and costs of competition. To characterise and quantify mortality and identify breed differences. Retrospective annualised cohort study. The Ontario Death Registry for 2003-2015, containing 1713 cases, was audited and information on the relationship between death and official work added. Race and trial data from industry performance databases were used to determine mortality rates according to breed, year, age, sex and circumstances of death. Breed differences in mortality rate and individual risk were found. Thoroughbreds (Tb) had the greatest exercise-associated mortality (EAM) rate and risk by all measures (2.27deaths/1000 race starts, 0.95-1.0% annual individual risk), followed by Quarter horses (Qh, 1.49, 0.60-0.69%). Rate and risk were lowest for Standardbreds (Sb, 0.28, 0.23-0.24%). Nonexercise annual individual risk was highest for the Sb (0.45%, vs. Tb 0.33%, and Qh 0.32%). Pattern and type of EAM mirrored the characteristics of competitive activity in each industry, with high Tb and Qh mortality being associated with exercise and involving musculoskeletal injuries, dying suddenly and accidents. Low Sb EAM reflected the more extensive nature of training preparation and racing for this breed. Available data provided no information on morbidity, mortality beyond the 60-day horizon or for horses not racing. Numbers for the Qh were low. Race-intensity exercise is clearly hazardous for horses, with hazards varying widely between breeds and showing parallels with industry cultural and management norms. Breed differences provide insights concerning strategies that could reduce mortality, while improving welfare and reducing costs of participation. For all breeds, musculoskeletal injury was the major contributing cause of mortality.

Haemangiosarcoma in two full sibling American Quarter Horse geldings

SummaryThis case report describes two full sibling gelding American Quarter Horses that presented separately for evaluation of an external mass (Case 1) and signs of colic and epistaxis (Case 2). The horses had the same owner and resided on the same property for the majority of their lives. Both horses were definitively or presumptively diagnosed antemortem with haemangiosarcoma, and on necropsy, multicentric (Case 1) and primary renal (Case 2) haemangiosarcoma were confirmed. A unique finding on necropsy was extensive bilateral renal involvement. Due to the low incidence of haemangiosarcoma in horses, the unique organ involvement and common ancestry of these two horses, a genetic cause is suspected.

Novel insights into Sabino1 and splashed white coat color patterns in horses.

SummaryWithin the framework of genome‐wide analyses using the novel Axiom® genotyping array, we investigated the distribution of two previously described coat color patterns, namely sabino1 (SBI), associated with the KIT gene (KI16+1037A), and splashed white, associated with the PAX3 gene (ECA6:g.11429753C>T; PAX3 C70Y), including a total of 899 horses originating from eight different breeds (Achal Theke, Purebred Arabian, Partbred Arabian, Anglo‐Arabian, Shagya Arabian, Haflinger, Lipizzan and Noriker). Based on the data we collected we were able to demonstrate that, besides Quarter horses, the PAX3 C70Y allele is also present in Noriker (seven out of 189) and Lipizzan (three out of 329) horses. The SB1 allele was present in three breeds (Haflinger, 14 out of 98; Noriker, four out of 189; Lipizzan one out of 329). Furthermore, we examined the phenotypes of SB1‐ and PAX3 C70Y‐carrier horses for their characteristic white spotting patterns. None of the SB1/sb1‐carrier horses met the criteria defining the Sabino1 pattern according to current applied protocols. From 10 heterozygous PAX3 C70Y‐carrier horses, two had nearly a splashed white phenotype. The results of this large‐scale experiment on the genetic association of white spotting patterns in horses underline the influence of gene interactions and population differences on complex traits such as Sabino1 and splashed white.

Geometric Properties of the Third Metacarpal Bone: A Comparison Between Thoroughbred and Quarter Horse Racehorses

A frequent reason that Thoroughbred racehorses are killed during racing or training is fracture of the third metacarpal (the cannon bone). Determining the factors involved in these catastrophic cannon bone fractures is imperative to improving both horse and jockey safety. Though seemingly spontaneous, catastrophic cannon bone fractures generally result from the combination of mechanical forces commonly present in racing Thoroughbreds, and generally materialize in the distal lateral condyle of the cannon bone. Thoroughbreds, however, are not the only breed of racehorse to experience catastrophic fractures—Quarter Horses also exhibit specific patterns of injury in more proximal limb bones. Different fracture patterns in these two breeds of galloping racehorse may indicate different loading patterns of their limbs, which could be a product of varied training programs, or variance in breed morphology. The present analysis compares geometric properties of the third metacarpal in Thoroughbred and Quarter Horse racehorses, using feral Assateague Island ponies as an outgroup, in order to clarify the reasons for distinctive fracture patterns in different breeds of racehorses.Six cannon bones from each breed were obtained from New Bolton Center (Thoroughbreds), Oklahoma State University (Quarter Horses), and the Assateague Island National Seashore (Assateague Island ponies). Peripheral Quantitative Computed Tomography (pQCT) generated cross sections at 40% and 20% (distal) of bone length, and at the midpoint of the distal articular surface. Cross‐sectional areas, second moments of area, and section moduli were calculated for the two diaphyseal sections, and trabecular bone mineral density and total bone mineral density were determined for the distal articular section. Approximate body masses were estimated from proximal articular breadths using a published formula.Analysis of covariance (ANCOVA) revealed that although the overall strength of cannon bones in Thoroughbreds and Quarter Horses did not differ relative to body size, Thoroughbreds had relatively higher anteroposterior bending strength in the diaphysis than Quarter Horses, and relatively lower mediolateral bending strength. Thoroughbreds also had lower values of trabecular and total bone densities in the distal articular section, which is the region where lateral condyle fractures are generally incurred by Thoroughbreds but not Quarter Horses. Both Thoroughbreds and Quarter Horses had lower overall safety factors compared to feral Assateague Island ponies. Assateague Island ponies exhibited relatively stronger bone shafts and a higher trabecular density in the distal articular section. Results suggest that breed‐specific bone structure differences contribute to the greater incidence of fractures in domestic racehorses and, relatedly, the common location of fractures in Thoroughbreds.Support or Funding InformationFunded by the American Society of Mammalogists.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of vaquejada exercise on the physiological and biochemical profiles of sporadic competitors and atletic horses

The aim of this study was to analyze the effect of a cycle of three races as a part of the vaquejada test, on the serum biochemistry of horses that compete sporadically and athletic horses. Fourteen Quarter Horses was evaluated: group 1 (G1), with seven horses from the region that competed sporadically and group 2 (G2), with seven horses that competed regulary and were transported for >200 km. The physiological and serum biochemistry parameters were evaluated before exercise (M0) and after a cycle of three races of the vaquejada test: immediately after (M1); 30 min (M2) and 120 min (M3) after. Wilcoxon test was used to assess differences between the groups and Friedman test for moment effects, with a significance level of 5%. There was increase in M1 compared with M0 for heart and respiratory rate in G2, and rectal temperature in G1. The exercise transiently changed most of the biochemical parameters, with significant diferences for uric acid in M1, albumin and lactate in M2, compared with M0, in G2. The metabolic response to exercise was different between the groups for the following variables: uric acid, total protein, albumin, unsaturated iron binding capacity, and transferrin saturation index. It was concluded that physiological and biochemical changes induced by Vaquejada are light, transiente, and within the normal range. The changes were more expressive in athletic horses that compete regularly and are transported, demonstrating the need for studies that establish specific training and management protocols for this category.

Metabolic and physiological changes during and after vaquejada exercise in horses

Physiological and metabolic evaluations of equine sports have been conducted to define parameters or biomarkers for performance evaluation, clinical diagnosis and predict fatigue and overtraining. Actually, the vaquejada is the most important equine sport in Brazil, and these horses are repeatedly submitted to shortduration physical exertion, during 2 or 3 alternate or consecutive days, requiring adequate conditioning for this equestrian modality. The objective of this study was to test the hypothesis that pulls horses and helper horses undergo physiological and metabolic changes during vaquejada races. Eighteen Quarter Horses were used, including 12 pull horses and 6 helper horses. Hemograms and the following analyses were performed: glucose, lactate, cholesterol, triglycerides, NEFA, total proteins, albumin, creatine kinase, gama glutamyl transferase and cortisol. A heart rate monitor was used to measure the heart rate, velocity and travel distance of each animal. Statistical analyses were performed using ANOVA and Tukey's tests, with P established at 5%. Pull horses had higher heart rate values, but the velocities attained by the two groups of horses were similar. There was an increase in heart rate, glucose, lactate, non-esterified fatty acids and cortisol in both pull and helper horses after racing, but these levels returned to resting values 30 minutes after the end of exercise. It was concluded that the vaquejada field test promoted significant changes in haematological, biochemical biomarkers and in the heart rate of both groups of horses.

A missense mutation in MYH1 is associated with susceptibility to immune-mediated myositis in Quarter Horses

BackgroundThe cause of immune-mediated myositis (IMM), characterized by recurrent, rapid-onset muscle atrophy in Quarter Horses (QH), is unknown. The histopathologic hallmark of IMM is lymphocytic infiltration of myofibers. The purpose of this study was to identify putative functional variants associated with equine IMM.MethodsA genome-wide association (GWA) study was performed on 36 IMM QHs and 54 breed matched unaffected QHs from the same environment using the Equine SNP50 and SNP70 genotyping arrays.ResultsA mixed model analysis identified nine SNPs within a ~ 2.87 Mb region on chr11 that were significantly (Punadjusted < 1.4 × 10− 6) associated with the IMM phenotype. Associated haplotypes within this region encompassed 38 annotated genes, including four myosin genes (MYH1, MYH2, MYH3, and MYH13). Whole genome sequencing of four IMM and four unaffected QHs identified a single segregating nonsynonymous E321G mutation in MYH1 encoding myosin heavy chain 2X. Genotyping of additional 35 IMM and 22 unaffected QHs confirmed an association (P = 2.9 × 10− 5), and the putative mutation was absent in 175 horses from 21 non-QH breeds. Lymphocytic infiltrates occurred in type 2X myofibers and the proportion of 2X fibers was decreased in the presence of inflammation. Protein modeling and contact/stability analysis identified 14 residues affected by the mutation which significantly decreased stability.ConclusionsWe conclude that a mutation in MYH1 is highly associated with susceptibility to the IMM phenotype in QH-related breeds. This is the first report of a mutation in MYH1 and the first link between a skeletal muscle myosin mutation and autoimmune disease.

Genomic regions associated with performance in racing line of Quarter Horses

Quarter Horses breed for rancing are able to run short distances faster than any other breed. Although in Brazil the effective number of animals in the racing line is relatively smaller compared to the other lines, its economic importance is substantial. Despite economic and scientific interest in this athletic trait, few efforts have been made to better understand the genetic and physiological mechanisms underlying this trait. The objective of this study was to perform genome-wide association studies (GWAS) in Quarter Horses of the racing line using equine single nucleotide polymorphism (SNP) genotyping chips for prospecting chromosome regions, genes and polymorphisms related to maximum speed index. Genotypic and phenotypic data from 305 horses genotyped with the 54 k or 65 k chip were used. Additional 187 not genotyped animal with SI record were added in the study, for a total of 492 animals and 620 horses in the pedigree used for the GWAS analysis GWAS was performed by the single-step genomic best linear unbiased prediction (ssGBLUP) method using two approaches: ssGWAS1 in which only SNP effects are recalculated at each iteration, and ssGWAS2 in which SNP effects are recalculated from updated genomic estimated breeding values (GEBVs) at each iteration. Twenty-one regions that explained more than 1% of the total genetic variance (gVar) in the maximum speed index were identified by ssGWAS1 and 12 by ssGWAS2. More than 40% of gVar was explained by these regions in ssGWAS1 and about 30% in ssGWAS2. Among chromosomes that explained more than 1% of genetic variance, five were common to both methods (equine autosomal chromosomes 3, 10, 15, 22, 25). The capacity to capture the largest number of small-effect quantitative trait loci was greater for ssGWAS1 than ssGWAS2. A total of 108 genes were identified with the first approach and 59 with the second approach. The present results show that the racing performance of Quarter Horses, given by the maximum speed index, is a quantitative trait and that no major genes exist. In general, the genes identified by enrichment analysis are related to the neuromotor system, bone and tendon development, hormonal responses, muscle contraction, and energy and sterol metabolism. These functions are considered important for the trait studied, corroborating these genes as candidates for racing performance in the Quarter Horse breed.

Histologic investigation of airway inflammation in postmortem lung samples from racehorses.

OBJECTIVE To describe histologic findings in the small airways during postmortem examination of actively racing horses and to quantify the degree of airway inflammation by use of a semiquantitative scoring system. SAMPLE Lung tissues obtained from 95 horses (Thoroughbreds, Standardbreds, and Quarter Horses) that had been actively racing or training. PROCEDURES 10 standardized lung sections were obtained during postmortem examination of 37 horses that had been actively racing or training, and 2 histologic sections of the caudodorsal lung lobes previously collected from each of 58 horses that died or were euthanized during racing or training were also obtained. Sections were evaluated by use of a validated histologic small airway scoring system. RESULTS Scores for inflammatory cells, smooth muscle, and hemosiderin typically were high. Signalment and cause of death were not significant predictors of lung scores. Lung sample location was a significant predictor, with the highest scores in the caudal and dorsal sections. Inflammatory cell infiltration in peribronchiolar tissues, smooth muscle hyperplasia, and hemosiderin (prevalence of 86%, 98%, and 80%, respectively) were common findings in lungs of these horses, with the caudodorsal regions more severely affected. Correlation was moderate between smooth muscle hyperplasia and inflammatory cell infltration, with minimal correlation between hemosiderin and inflammatory cell infiltration. CONCLUSIONS AND CLINICAL RELEVANCE Inflammatory airway disease has been identified by use of bronchoalveolar lavage in young athletic horses throughout the world. In the study reported here, pathological changes were detected in the wall of small airways of horses that were actively training or racing.

Effects of Feeding Frequency Using a Commercial Automated Feeding Device on Gastric Ulceration in Exercised Quarter Horses

The objective of this study was to evaluate two feeding regimens: traditional grain feeding (twice a day, traditional fed [TF]) compared with horses fed with an automated feeder programmed to deliver grain in 20 equal aliquots (fractioned fed [FF]) and its effects on gastric ulceration, body weight, and body condition score (BCS). Thirty-one Quarter Horses were maintained in individual stalls during the 60-day experimental period and worked at moderate exercise intensity. Gastroscopies were performed before grain adaptation at 0, 30, and 60 days. Weight and BCS were evaluated biweekly. There were no changes in squamous (equine squamous gastric disease [ESGD]) ulcers in FF horses over the study period and higher ESGD ulcer scores in TF horses over both the 30 and 60-day time points. The proportion of horses with equine glandular gastric disease (EGGD) were significantly lower with fractioned feed when compared with traditional feed on day 30, but no difference was seen at day 60. No significant differences were found when comparing the two groups for BCS or body weight throughout the study period. This study further supports that fasting period is a strong contributing factor for gastric ulcer formation. FF of the daily total grain led to a decrease in time fasting when compared with TF which reduced the severity and incidence of both ESGD and EGGD. The use of the commercial feeder for FF may aid in lessening prevalence of gastric ulcers in young training Quarter Horses.

Anatomic analysis of the equine mental foramen and rostral mandibular canal using computed tomography

ObjectivesTo characterize the anatomy of the mental foramen and determine associations with age, weight, sex and breed. Study designRetrospective descriptive study. AnimalsForty-one horses, 0.6–25.2 years and weighing 136–820 kg. MethodsComputed tomography (CT) studies of equine heads performed over 5 years were evaluated in multiplanar and three-dimensional reconstruction. Measurements obtained were positioning of the foramen along the mandible, foramen height and width, foramen–canal angulation and rostral canal mineralization. Exploratory statistical analyses investigated associations between measurements and age, weight, sex and breed. ResultsEvaluation of 41 CT studies revealed foramen positioning was one-third of the horizontal distance of the incisor–premolar space from the second premolar and one-third of the vertical distance in the mandible from the dorsal surface of interproximal space at the level of the foramen. Age was negatively correlated to horizontal positioning [r = –0.42; 95% confidence intervals (CI), –0.64 to –0.13]. Mean foramen width was 6.4 (range, 2.3–17.1) mm and height 5.6 (range, 2.1–10.3) mm. Age and foramen height (r = 0.32; 95% CI, 0.01 to 0.57) and width (r = 0.30; 95% CI, –0.01 to 0.30) were positively correlated. Thoroughbred and Warmblood/Draft horses had increased foramina heights compared with Quarter horses [analysis of variance (anova)p = 0.02]. Males had wider foramina (95% CI, –2.66 to 0.07). Angulation of the foramen–canal was mean ± standard deviation 68.3 ± 12.8° (range, 37.9–105.6°) transverse plane, 28.3 ± 4.1° (range, 18.2–39.0°) saggital plane and 41.4 ± 8.45° (range, 22.2–58.6°) dorsal plane. Older horses had decreased mineralization of the rostral canal (anova, left p = 0.015, right p = 0.025). ConclusionsThe size, shape, positioning and angulation of the mental foramen varies. Mineralization of the canal is decreased in older horses. Clinical relevanceThis study improves understanding of mental foramen anatomy and complications with needle placement.

Evaluation of conjugated linoleic acid supplementation on markers of joint inflammation and cartilage metabolism in young horses challenged with lipopolysaccharide.

Seventeen yearling Quarter Horses were used in a randomized complete block design for a 56-d trial to determine ability of dietary CLA to mitigate joint inflammation and alter cartilage turnover following an inflammatory insult. Horses were blocked by age, sex, and BW, and randomly assigned to dietary treatments consisting of commercial concentrate offered at 1% BW (as-fed) supplemented with either 1% soybean oil (CON; n = 6), 0.5% soybean oil and 0.5% CLA (LOW; n = 5; 55% purity; Lutalin, BASF Corp., Florham Park, NJ), or 1% CLA (HIGH; n = 6) top-dressed daily. Horses were fed individually every 12 h and offered 1% BW (as-fed) coastal bermudagrass (Cynodon dactylon) hay daily. This study was performed in 2 phases: phase I (d 0 to d 41) determined incorporation of CLA into plasma and synovial fluid; phase II (d 42 to d 56) evaluated potential of CLA to mitigate intra-articular inflammation and alter cartilage metabolism. Blood and synovial fluid were collected at 7- and 14-d intervals, respectively, to determine fatty acid concentrations. On d 42, carpal joints within each horse were randomly assigned to receive intra-articular injections of 0.5 ng lipopolysaccharide (LPS) derived from Escherichia coli 055:B5 or sterile lactated Ringer's solution. Synovial fluid samples were obtained at preinjection h 0 and 6, 12, 24, 168, and 336 h postinjection, and analyzed for prostaglandin E2 (PGE2), carboxypeptide of type II collagen (CPII), and collagenase cleavage neopeptide (C2C). Data were analyzed using PROC MIXED procedure of SAS. Horses receiving the CON diet had undetectable levels of CLA for the duration of the study. A quadratic dose response was observed in concentrations of CLA in plasma and synovial fluid (P < 0.01). A negative quadratic dose response was observed for plasma arachidonic acid (20:4) with a reduction in concentration to d 14 in HIGH horses (P = 0.04). Synovial fluid 20:4 tended to decrease in horses receiving the HIGH diet (P = 0.06). Post LPS injection, synovial PGE2 was not affected by dietary treatment (P = 0.15). Synovial C2C was lower in HIGH horses (P = 0.05), and synovial CPII tended to be greater in LOW horses than HIGH and CON horses (P = 0.10). In conclusion, dietary CLA incorporated into plasma and synovial fluid prior to LPS challenge. Dietary CLA did not influence inflammation; however, there was a reduction in cartilage degradation and an increase in cartilage regeneration.

Frequency distribution of osteochondral fragmentation of the dorsoproximal articular surface of the proximal phalanx in racing Thoroughbreds in the UK.

Osteochondral fragmentation of the dorsoproximal margin of the proximal phalanx is commonly recognised in racing Thoroughbreds. Frequency distribution has been documented in racing Thoroughbreds and Quarter Horses in the USA and in European Warmbloods but no data have been published from the UK. Concurrent intra-articular soft tissue lesions and radiographic accuracy of fragment distribution in racing Thoroughbreds have not previously been reported. To document frequency distribution of dorsoproximal fragmentation of the proximal phalanx in a UK population of racing Thoroughbreds and to compare this with published data. To document concurrent intra-articular lesions identified arthroscopically and radiographic accuracy of fragment distribution. A retrospective single centre-based, observational study. Surgical reports and radiographs of all racing Thoroughbreds that underwent arthroscopic surgery for removal of fragmentation from the dorsoproximal margin of the proximal phalanx at Newmarket Equine Hospital between 2011 and 2015 were reviewed. Two hundred and forty-two (85.8%) horses were in or being prepared for flat racing. Osteochondral fragmentation of the dorsoproximal aspect of the proximal phalanx was present in 428 fetlock joints of 282 horses, consisting of 194 (45.3%) left and 188 (43.9%) right metacarpophalangeal joints, and 20 (4.7%) left and 26 (6.1%) right metatarsophalangeal joints. Fragmentation was located dorsomedially in 316 (73.8%), dorsolaterally in 32 (7.5%) and biaxially in 80 (18.7%) joints. Concurrent soft tissue lesions were identified in 168 (39.3%) joints. Radiographic evidence of fragmentation was visible in 320 joints (74.8%). Limited numbers preclude conclusions with respect to yearlings and horses in jump race training. Dorsoproximal fragmentation of the proximal phalanx occurred most frequently medially and in the forelimbs. Sidedness was not demonstrated. Although similar to previously reported data, variance in limb distribution is evident. Further research is required to determine whether concurrent intra-articular soft tissue lesions are aetiopathogenic or an additional result of the pathological changes leading to fragmentation. Fragmentation site was not always accurately identified radiographically. The Summary is available in Spanish - see Supporting information.

Assessment of Equine Feeding Practices and Knowledge of Equine Nutrition in the Midwest

Equine owner's and manager's implementation of equine nutrition concepts varies across disciplines and geographic regions. The project objectives were to (1) characterize equine feeding practices in the Upper Midwest; and (2) determine the extent to which horse owners and managers in the Upper Midwest were knowledgeable in the area of equine nutrition. An online survey was open to equine owners and managers 18+ years of age in South Dakota and neighboring states. Respondents were mainly female (85%, n = 150), had an average age of 40 ± 16 years (n = 145), had over 10 years of equine ownership/management experience (71%, n = 131), and belonged to one equine organization on average. When respondents identified a representative horse from their herd, Quarter Horses with an average age of 12 ± 6 years were most commonly reported. The majority of owners (57%, n = 127) reported that their horses were kept at maintenance or in light work. Respondents' methods of estimating horse weight and body condition score, measuring and analyzing feedstuffs, and managing pastures varied. Nutrition knowledge score averaged 10.8 ± 3.1 out of 20 possible points. Knowledge score was not correlated with number of horses owned/managed or years of horse experience (P > .10), but there was a slight positive correlation with equine organization involvement (P = .02). This survey characterized feeding practices in the Upper Midwest noting some discrepancies between respondents' knowledge and how they feed their horses. Opportunities exist for improving understanding and application of equine nutrition concepts.

Acute responses of iron indices in Quarter Horses during a 3-barrel racing exercise

Energy metabolism and physical performance are dependent on sufficient iron metabolism. Therefore, studies evaluating the iron profile are necessary to elucidate this trace mineral requirements and its role in the equine exercise physiology. The aim of this study was to evaluate the influence of barrel racing exercise on serum iron profile of Quarter horses. Twenty-two regularly trained Quarter horses (8 females and 14 males, 4.8 ± 2.4 years old, mean body weight 431.7 ± 33.9 kg) were enrolled in this study with the owner’s informed consent. All horses were evaluated at T0 (at rest), T1 (immediately after barrel racing trial), T2 (30 min after trial) and T3 (2 h after trial). At these time points, blood samples were taken to determine the packed cell volume (PCV), red blood cell count (RBC), haemoglobin concentration (Hb), total protein (TP), serum iron (SI), total iron-binding capacity (TIBC) and transferrin saturation (TSAT). Variables were analyzed for normality through Kolmogorov-Smirnov test and comparisons were made using Tukey test, considering P &lt; 0.05. The imposed exercise challenge significantly altered PCV, RBC, haemoglobin concentration, TP, SI and TSAT, with higher values were recorded at T1. These findings can be linked to an increased demand as a result of physical activity. Significant changes occurred in the iron status in physically well-conditioned Quarter horses during the barrel racing exercise. Better understanding of iron metabolism in horses will help determine the actual necessity of supplementation.

Evolución cicatricial de herida lacerante con exposición ósea en equino. Reporte de caso

This article aims to report a case of large laceration with great loss of skin at the dorsal medial portion of the right pelvic member, with partial exposure of the metatarsal and the long extensor tendon of the fingers in a mare of Quarter Horses 8 months of age. It was prescribed a treatment based on antibiotics and anti-inflammatory, and healing on alternate days through tranquilization with detomidine. The initial contamination associated with the size and magnitude of the injury, contributed to delayed wound healing for 170 days, and repeated and prolonged use of detomidine did not cause cardiovascular changes at the patient.

Relationship between repository radiographic findings and subsequent performance of Quarter Horses competing in cutting events.

OBJECTIVE To investigate potential associations between repository radiographic findings and subsequent performance of Quarter Horses competing in cutting events. DESIGN Retrospective cohort study. SAMPLE Repository radiographs (ie, radiographs obtained at the time of sale) for 343 client-owned horses. PROCEDURES Repository radiographic findings were compared with objective measures of performance, including the likelihood of competing; the likelihood of earning money as a 3-year-old, as a 4-year-old, and as a 3- and 4-year-old combined; and the amount of money earned as a 3-year-old, as a 4-year-old, and as a 3- and 4-year-old combined. RESULTS The presence of mild osteophytes involving the distal aspect of the tarsal joint was significantly associated with lower mean earnings as a 4-year-old. The presence of osteophytes on the dorsoproximal aspect of the middle phalanx of the hind limbs was significantly associated with an increased odds of earning money as a 4-year-old. Radiographic lesions of the medial femoral condyle of the stifle joint were not significantly associated with subsequent performance. CONCLUSIONS AND CLINICAL RELEVANCE Most abnormalities identified on repository radiographs were not significantly associated with subsequent performance. The significant association between mild tarsal osteophytosis and earnings was unexpected. Results of the present study indicated the need for further investigation of the relationship between radiographic findings and performance outcome in Western performance horses.

Skeletal muscle from aged American Quarter Horses shows impairments in mitochondrial biogenesis and expression of autophagy markers

Aging is associated with decreased mitochondrial content and function in skeletal muscle, possibly due to compromised biogenesis and autophagic removal of dysfunctional mitochondria. The aim of this study was to compare markers of mitochondrial content and biogenesis and of autophagy between skeletal muscle from young and aged American Quarter Horses. Citrate synthase protein and mtDNA copy number were decreased in triceps brachii (TB) muscle (P<0.05) from aged horses, suggesting an age-related decline in mitochondrial content. Concomitantly, mRNA expression of PGC-1α and TFAM, regulators of mitochondrial biogenesis, was lower in aged compared to young TB (P<0.05). Expression of autophagy markers suggested an age-associated decline of autophagy. The autophagosomal cargo protein SQSTM/p62 accumulated with age in both muscles (P<0.05). Expression of Autophagy-related protein Atg5 (P<0.05) and the autophagosome-bound form of Microtubule-associated protein light chain 3 (LC3-II; P<0.05) were lower in aged compared to young TB. While LC3 transcript level was elevated in aged compared to young GM (P<0.001), protein expression of LC3-II was unaffected. Gene expression of Lysosomal Membrane-Associated Protein 2 (LAMP2) was not affected by age in either muscle. However, LAMP2 protein expression declined with age (P<0.05), suggesting a decline in autophagosome-lysosome fusion. Taken together, our data indicate that equine skeletal muscle mitochondrial content and biogenesis were impaired with age. Further, autophagosome formation and lysosomal degradation were negatively affected in aged TB and GM, respectively. Future research needs to explore whether interventions targeting these cellular processes can prolong health and performance of aging American Quarter Horses.

Workload of horses on a water treadmill: effect of speed and water height on oxygen consumption and cardiorespiratory parameters

BackgroundDespite the use of water treadmills (WT) in conditioning horses, the intensity of WT exercise has not been well documented. The workload on a WT is a function of water height and treadmill speed. Therefore, the purpose of this study was to determine the effects of these factors on workload during WT exercise.Fifteen client-owned Quarter Horses were used in a randomized, controlled study. Three belt speeds and three water heights (mid cannon, carpus and stifle), along with the control condition (dry treadmill, all three speeds), were tested. Measured outcomes were oxygen consumption (V̇O2), ventilation (respiratory frequency, tidal volume (VT)), heart rate (HR), and blood lactate. An ergospirometry system was used to measure V̇O2 and ventilation. Linear mixed effects models were used to examine the effects of presence or absence of water, water height and speed (as fixed effects) on measured outcomes.ResultsWater height and its interaction with speed had a significant effect on V̇O2, VT and HR, all peaking at the highest water level and speed (stifle at 1.39 m/s, median V̇O2 = 16.70 ml/(kg.min), VT = 6 L, HR = 69 bpm). Respiratory frequency peaked with water at the carpus at 1.39 m/s (median 49 breaths/min). For a given water height, the small increments in speed did not affect the measured outcomes. Post-exercise blood lactate concentration did not change.ConclusionsVarying water height and speed affects the workload associated with WT exercise. The conditions utilized in this study were associated with low intensity exercise. Water height had a greater impact on exercise intensity than speed.

Effect of various levels of dietary starch on glycogen replenishment in the light working horse

ABSTRACT Nine Quarter Horses were used in a 3 × 3 Latin square with replication to determine the effect of various levels of dietary starch on glycogen replenishment in the light working horse. Horses were fed Coastal bermudagrass hay at 1% BW/d with remaining calories met by a high (HS), medium (MDS), or low starch (LS) concentrate. Horses were transitioned to 1 of 3 diets over 7 d for a 14-d treatment period where they were then worked to fatigue in a standardized exercise test. Total diets provided an average of 1,206.67, 844.61, and 263.13 g of starch/d in HS, MDS, and LS, respectively. Horses were lightly exercised for 30 min 3 d/wk. Skeletal muscle biopsies were taken from the biceps femoris at rest, immediately after the standardized exercise test, and 24 and 48 h after exercise. Venous blood samples were taken at rest, immediately after exercise, 10 min after recovery, and 24 h after exercise. There was a greater resting muscle glycogen concentration (P = 0.009) when comparing HS with MDS (10.25 vs. 8.28 μg/mg wet weight). There was a greater concentration of glycogen 24 h after exercise (P = 0.04) when comparing LS with HS (9.52 vs. 7.68 μg/mg wet weight). High starch used more glycogen than MDS or LS. A slight reduction in glycogen after exercise for MDS and LS indicated that fat or protein may have been used as substrate for exercise. Results indicated that feeding 1,206.67 g of starch/d did not yield an advantage in recovery time over a MDS or LS diet.