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Background Inflammatory airway disease ( IAD) affects performance and well-being of horses. Diagnosis is primarily reached by bronchoalveolar lavage ( BAL) cytology which is invasive and requires sedation. Objectives The purpose of this study was to identify differential gene expression in peripheral blood of horses with IAD using species-specific expression microarrays. Methods Equine gene expression microarrays were used to investigate global mRNA expression in circulating leukocytes from healthy, IAD-affected, and low-performing Standardbred and endurance horses. Results Nine genes in Standardbred and 61 genes in endurance horses were significantly differentially regulated ( P < .001). These genes were related to inflammation (eg, ALOX15B, PLA2G12B, and PENK), oxidant/antioxidant balance (eg, DUOXA2 and GSTO1-1), and stress (eg, V1aR, GRLF1, Homer-2, and MAOB). All these genes were up-regulated, except down-regulated Homer-2 and MAOB. DUOXA2, ALOX15B, PLA2G12B, MAOB, and GRLF1 expression was further validated by RT- qPCR. An increase in glutathione peroxidase (GPx) activity in heparinized whole blood of IAD-affected Standardbred ( P = .0025) and endurance horses ( P = .0028) also suggests a deregulation of the oxidant/antioxidant balance. There was good correlation ( r = .7354) between BAL neutrophil percentage and whole blood GPx activity in all horses. Conclusions This study showed that circulating blood cell gene expression reflects inflammatory responses in tissues. Whether any of the genes have potential for diagnostic applications in the future remains to be investigated. Although not specific for IAD, whole blood GPx activity appears to be correlated with BAL neutrophil percentage. This finding should be further assessed by testing a larger number of horses. [ABSTRACT FROM AUTHOR]

Abstract: Utilising a face-to-face interview of stud managers, a survey was conducted to investigate the movement patterns around, and biosecurity practices on, Thoroughbred and Standardbred stud farms. Eligible stud farms (n =60) were identified from the 2009 Thoroughbred stallion register and 2009 Standardbred stallion register, and stud managers were asked to participate in the interview. In total, 27 stud managers agreed to participate in the study, and participating stud farms included 38% of Thoroughbred and 60% of Standardbred mares bred in 2009. All stud managers reported the movement of horses to and from their stud farm. The median number of movement events per year was 127 (interquartile range 83–300). The frequency of movement events from a stud farm was not associated with the breed of horse managed on the stud farm, however Thoroughbred horses travelled further than Standardbred horses during these movement events (P <0.001). The movement patterns of horses around stud farms showed a strong seasonality associated with the commercial breeding season of each breed. While 26 (96%) of stud managers reported having procedures in place for checking newly arriving horses, only 6 (22%) stud managers reported isolating horses on arrival as a standard protocol. The main reason for isolating horses on properties, where isolation was not a standard procedure, was in response to strangles outbreaks on other stud farms (n =10). Only 2 (7%) stud managers reported implementing visitor protocols, and these protocols only applied to visiting veterinarians, but not to farriers. These findings have important implications for the control of both endemic and exotic infectious disease outbreaks within the New Zealand breeding population as the high frequency of movement around stud farms, the high number of visitors to stud farms and the lack of effective biosecurity practices or visitor protocols will be critical factors in the spread of equine influenza during an outbreak. [Copyright &y& Elsevier]

Endocrinopathic laminitis is frequently associated with hyperinsulinaemia but the role of glucose in the pathogenesis of the disease has not been fully investigated. This study aimed to determine the endogenous insulin response to a quantity of glucose equivalent to that administered during a laminitis-inducing, euglycaemic, hyperinsulinaemic clamp, over 48 h in insulin-sensitive Standardbred racehorses. In addition, the study investigated whether glucose infusion, in the absence of exogenous insulin administration, would result in the development of clinical and histopathological evidence of laminitis. Glucose (50% dextrose) was infused intravenously at a rate of 0.68 mL/kg/h for 48 h in treated horses (n = 4) and control horses (n = 3) received a balanced electrolyte solution (0.68 mL/kg/h). Lamellar histology was examined at the conclusion of the experiment. Horses in the treatment group were insulin sensitive (M value 0.039 ± 0.0012 mmol/kg/min and M-to-I ratio (100x) 0.014 ± 0.002) as determined by an approximated hyperglycaemic clamp. Treated horses developed glycosuria, hyperglycaemia (10.7 ± 0.78 mmol/L) and hyperinsulinaemia (208 ± 26.1 μIU/mL), whereas control horses did not. None of the horses became lame as a consequence of the experiment but all of the treated horses developed histopathological evidence of laminitis in at least one foot. Combined with earlier studies, the results showed that laminitis may be induced by either insulin alone or a combination of insulin and glucose, but that it is unlikely to be due to a glucose overload mechanism. Based on the histopathological data, the potential threshold for insulin toxicity (i.e. laminitis) in horses may be at or below a serum concentration of 200 μIU/mL. [ABSTRACT FROM AUTHOR]

Our objective in this study is to compare 4 of the most common bedding materials used by equine operations on the chemical and physical characteristics of composted equine stall waste. Twelve Standardbred horses were adapted to the barn and surrounding environment for 2 wk before the start of the study. Groups of 3 horses were bedded on 1 of 4 different bedding types (wood shavings, pelletized wood materials, long straw, and pelletized straw) for 16 h per day for 18 d. Stalls were cleaned by trained staff daily, and all contents removed were weighed and stored separately by bedding material on a level covered concrete pad for the duration of the study. Compost piles were constructed using 3 replicate piles of each bedding type in a randomized complete block design. Each pile was equipped with a temperature sensor and data logger. Water was added and piles were turned weekly throughout the 100-d compost process. Initial and final samples were taken, dried, and analyzed for DM mass, OM, inorganic nitrogen (nitrate-N and ammonium-N), electrical conductivity, and soluble (plant-available) nutrients. Data were analyzed using the GLM procedure, and means were separated using Fischer's protected LSD test (P < 0.05). No significant temperature differences were observed among the bedding materials. The composting process resulted in significant reductions (P < 0.05) in DM mass for each of the 4 bedding materials. The composting process resulted in significant reductions (P < 0.05) in OM and C:N ratio for all 4 bedding materials. The composted long straw material had greater concentrations of total Kjeldahl nitrogen (P < 0.05), nitrate-N (P < 0.05), and ammonium-N (P < 0.05) than the composted wood shavings. This study demonstrated that incorporating a simple aerobic composting system may greatly reduce the overall volume of manure and yield a material that is beneficial for land application in pasture-based systems. The straw-based materials may be better suited for composting and subsequent land application; however, factors such as suitability of the bedding material for equine use, material cost, labor, and availability must be considered when selecting a bedding material. [ABSTRACT FROM AUTHOR]

A system for identifying equine major histocompatibility complex (MHC) haplotypes was developed based on five polymorphic microsatellites located within the MHC region on ECA 20. Molecular signatures for 50 microsatellite haplotypes were recognized from typing 353 horses. Of these, 23 microsatellite haplotypes were associated with 12 established equine leucocyte antigen (ELA) haplotypes in Thoroughbreds and Standardbreds. Five ELA serotypes were associated with multiple microsatellite subhaplotypes, expanding the estimates of diversity in the equine MHC. The strong correlations between serological and microsatellite typing demonstrated a linkage to known MHC class I protein polymorphisms and validated this assay as a useful supplement to ELA serotyping, and in some applications, a feasible alternative method for MHC genotyping in horse families and in population studies. [ABSTRACT FROM AUTHOR]

Osteochondrosis (OC), a disturbance in the process of endochondral ossification, is by far the most important equine developmental orthopaedic disease and is also common in other domestic animals and humans. The purpose of this study was to identify quantitative trait loci (QTL) associated with osteochondrosis dissecans (OCD) at the intermediate ridge of the distal tibia in Norwegian Standardbred (SB) using the Illumina Equine SNP50 BeadChip whole-genome single-nucleotide polymorphism (SNP) assay. Radiographic data and blood samples were obtained from 464 SB yearlings. Based on the radiographic examination, 162 horses were selected for genotyping; 80 of these were cases with an OCD at the intermediate ridge of the distal tibia, and 82 were controls without any developmental lesions in the joints examined. Genotyped horses descended from 22 sires, and the number of horses in each half-sib group ranged from 3 to 14. The population structure necessitated statistical correction for stratification. When conducting a case-control genome-wide association study (GWAS), mixed-model analyses displayed regions on chromosomes ( Equus callabus chromosome - ECA) 5, 10, 27 and 28 that showed moderate evidence of association ( P ≤ 5 × 10; this P-value is uncorrected i.e. not adjusted for multiple comparisons) with OCD in the tibiotarsal joint. Two SNPs on ECA10 represent the most significant hits (uncorrected P = 1.19 × 10 in the mixed-model). In the basic association (chi-square) test, these SNPs achieved statistical significance with the Bonferroni correction ( P = 0.038) and were close in the permuted logistic regression test ( P = 0.054). Putative QTL on ECA 5, 10, 27 and 28 represent interesting areas for future research, validation studies and fine mapping of candidate regions. Results presented here represent the first GWAS of OC in horses using the recently released Illumina Equine SNP50 BeadChip. [ABSTRACT FROM AUTHOR]

The objectives of this study were to determine the prevalence of sub-clinical diseases in poorly-performing Standardbred horses, compare their physiological response to exercise with control horses, and identify predictive parameters of poor-performance. Fifty horses underwent thorough clinical and ancillary examinations, including haematological and biochemical evaluation, Doppler echocardiography, standardised exercise tests (SETs) on both treadmill and racetrack, treadmill video-endoscopy and collection of respiratory fluids. Most of the poorly-performing horses exhibited many concomitant diseases. The most frequently diagnosed problems involved the lower and upper respiratory tract and the musculoskeletaI system. Poor performers bad lower speeds at a blood lactate (LA) concentration of 4 mmol/L (VLAL4) and a heart rate (HR) of 200 bpm (V200) on treadmill and racetrack, as well as lower values for haematological parameters, plasma angiotensin-converting enzyme and antioxidants, compared to control horses. Problems of the respiratory system were the most frequently diagnosed sub-clinical diseases affecting performance. SETs, together with some blood markers, may be useful as a non-specific diagnostic tool for early detection of diseases that may affect performance. [ABSTRACT FROM AUTHOR]

Abstract: Proper identification of racehorses competing in an official race and maintenance of defensible chain of custody are important in doping control regulations. The purpose of this study was to develop a reliable multiplex PCR method for providing genetic evidence for matching donors to test samples by using short tandem repeat (STR) loci. Amplification of 21 STR loci from blood, urine or hair root was achieved in a single tube and STR length polymorphism was analyzed using fluorescent labeled capillary electrophoresis. This novel approach showed an allele confidence interval of 0.19–0.43bp and size estimation error of 0–0.48bp. In 90 thoroughbred (TB) and 171 standardbred (STB) horses, the method was highly discriminating and reproducible with probability of false identification of 1 in 1011 (TB) and 1 in 1013 (STB). All loci were highly polymorphic with an average probability of identity of 0.18 (TB) and 0.13 (STB), heterozygosity of 0.65 (TB) and 0.68 (STB), and polymorphism information content (PIC) of 0.62 (TB) and 0.69 (STB). The highest allele frequency also reflected the degree of polymorphism due to high correlation with PIC. To obtain evidence of sample tampering with human material, three human specific STR markers were included in the panel. This method is the first in the horseracing industry, specifically designed for racehorse identification and detection of equine sample contamination by human DNA. [Copyright &y& Elsevier]

Previous studies of the effect of age on maximal aerobic capacity (maximal rate of oxygen consumption, VO2max) in horses have only grouped horses (young, middle-aged and old) for statistical analysis. Those experiments were not designed to determine a break point due to age. The purpose of this study was to utilize data collected over the last 15 years to test the nature of the association between age and VO2max, and secondarily, to determine whether there is a 'breakpoint' in the age-related decline in aerobic capacity. Data were acquired from 50 unfit Standardbred mares ranging in age from 4 to 29 years, and were used in a retrospective regression analysis in order to characterize the age-related decline in VO2max. All VO2max values were measured using the same incremental graded exercise test protocol. The data were analyzed using a curvilinear regression analysis predicting VO2max from age, and the break point was determined using univariate simple contrasts. There was a significant decline in VO2max with age (R² = 0.554; P < 0.001). The data analysis demonstrated a notable downturn in cardiopulmonary function between the ages of 18 and 20 years (P < 0.001). Such results indicate similar responses to age between humans and horses. These results have implications for improving training methods in active older horses. [ABSTRACT FROM AUTHOR]

This study hypothesized that ginger (Zingiber officinale) and cranberry (Vaccinium macrocarpon) extracts would alter the physiological response to exercise as well as markers of muscle damage, and mRNA expression for the inflammatory cytokines tumour necrosis factor-α (TNF-α), interferon-γ (IFN-γ) and interleukin-6 (IL-6) after an exhaustive bout of exercise in horses. Nine unfit Standardbred mares (age 10 ± 4 years, ∼450 kg) completed three graded exercise tests (GXTs) in a crossover design, where they were assigned to the initial order of treatment in a randomized fashion. The GXTs were conducted between 07.00 and 12.00 hours, 7 days apart. Mares received either water (2 l), cranberry (∼30 g in 2 l of water) or ginger (∼30 g in 2 l of water) extract 1 h prior to testing. Blood samples were taken prior to dosing (pre-exercise), at the end of each step of the GXT, at the end of the exercise and at 2, 5 and 30 min, 1, 2, 4 and 24 h post-GXT. Plasma total protein (TP) concentration and haematocrit (HCT) were analysed immediately following the tests. Analysis of creatine kinase (CK) and aspartate aminotransferase (AST) was done commercially. There was no effect of treatment (P>0.05) on VO2max, run-time to fatigue, core temperature, TP or HCT. CK was substantially elevated (P < 0.05) in the ginger group at 4 h post-GXT. All CK levels returned to baseline 24 h post-GXT. No change (P>0.05) was noted in AST. A slight increase (P < 0.05) in CK was seen in all groups at 2 h post-GXT. The cranberry group had significantly lower TNF-α mRNA expression than the control and ginger groups. Ginger appeared to influence (P < 0.05) the upregulation and expression of IFN-γ mRNA at 30 min post-GXT, but, more strikingly, significantly decreased recovery time defined as the time for VO2 to recover from the peak observed at fatigue to a post-exercise plateau (ginger = 101 ± 3 s, water = 130 ± 14 s, cranberry = 131 ± 16 s). No effect of treatment or exercise (P>0.05) was seen on IL-6 mRNA expression. Results suggest that cranberry extract blunts the upregulation and expression of TNF-α mRNA, while ginger extract reduces cardiovascular recovery time in horses completing a short, exhaustive bout of exercise. [ABSTRACT FROM AUTHOR]

Abstract: Glutamine plays important roles in the interorgan transport of nitrogen, carbon and energy but little is known about glutamine metabolism in the horse. In this study we determined the tissue distribution of glutamine synthetase expression in three Standardbred mares. Expression of glutamine synthetase was highest in kidney and mammary gland, and relatively high in liver and adipose tissue. Expression was lower in gluteus muscle, thymus, colon and lung, and much lower in small intestine, pancreas and uterus. The pattern of glutamine synthetase expression in the horse is similar to that of other herbivores and it is likely that skeletal muscle, liver, adipose tissue and lungs are the major sites of net glutamine synthesis in this species. Expression did not differ between adipose tissue depots but did vary between different muscles. Expression was highest in gluteus and semimembranous muscles and much lower in diaphragm and heart muscles. The concentration of intramuscular free glutamine was inversely correlated with expression of glutamine synthetase (r =−0.81, p =0.0017). The concentration of free glutamine was much higher in heart muscle (21.6±0.9 μmol/g wet wt) than in gluteus muscle (4.19+0.33 μmol/g wet wt), which may indicate novel functions and/or regulatory mechanisms for glutamine in the equine heart. [Copyright &y& Elsevier]

Ponies and some horse breeds such as Andalusians exhibit an 'easy keeper' phenotype and tend to become obese more readily than other breeds such as Standardbreds. Various hypotheses have been proposed, including differences in appetite or metabolic efficiency. This study aimed to investigate the effect of breed on nutrient digestibility. Ponies, Standardbreds and Andalusian horses were adapted to consuming either a control fibre-based diet (n = 9), a hypercaloric cereal-rich diet (n = 12) or a hypercaloric fat-rich diet (n = 12) over 20 weeks. Total faecal collection was performed over 24 h to determine apparent total tract digestibility of gross energy, dry matter (DM), neutral detergent fibre (NDF), starch, crude protein and crude fat. There was no effect of breed on apparent digestibility for any of the nutrients studied (all p > 0.05). However, there was a significant effect of diet, with animals consuming the cereal-rich or fat-rich diets demonstrating higher digestibility of gross energy, DM, NDF and crude protein compared with those consuming the control diet (all p < 0.05). Animals adapted to the cereal-rich diet demonstrated higher digestibility of starch (p < 0.001) and animals adapted to the fat-rich diet demonstrated higher digestibility of fat (p < 0.001). This study found that horses and ponies had similar nutrient digestibility when adapted to the same diets and management conditions. Limitations included the relatively small number of animals from each breed per diet group and the short period of total faecal collection. The tendency towards increased adiposity in ponies and Andalusian-type horse breeds is more likely to reflect differences in metabolism, rather than differences in feed digestibility. [ABSTRACT FROM AUTHOR]