Oxidative Stress and Antioxidant Status in Standardbreds: Effect of Age and Training in Resting Plasma and Muscle

The hypothesis of this study was that yearlings would have more oxidative stress as measured by malondialdehyde (MDA), total glutathione (GSH-T), glutathione peroxidase (GPx), and nitric oxide (NO) than mature mares before training, but after they would have similar levels. Ten Standardbred yearling fillies and 10 mature Standardbred mares were split into trained and nontrained groups. Horses were trained 5 days/wk for 7 weeks. Blood and muscle samples were collected at rest on weeks 0, 2, 5, 7, and 9. At week 0, the yearlings had higher muscle GSH-T and NO concentrations (P = .03) than the trained mares. At week 9, plasma NO concentrations were lower in trained mares than in the trained yearlings (P = .007). Trained mares increased muscle MDA and decreased plasma MDA concentrations from weeks 0 to 9 (P < .01), while all mares increased muscle NO and GSH-T concentrations by week 9 (P < .05). Trained mares and yearlings had increased erythrocyte GPx activity at weeks 7 and 9 and GSH-T concentration at week 7 (P < .05). Mares had higher lipid peroxidation and lower antioxidant status in the muscle than the yearlings prior to training. Trained mares improved antioxidant status and oxidative stress levels through training, resulting in levels similar to the yearlings.     

Antioxidant status in hyperthyroid cats before and after radioiodine treatment

Background

Reversible antioxidant depletion is found in hyperthyroid humans, and antioxidant depletion increases the risk of methimazole toxicosis in rats.

Objectives

To determine whether abnormalities in concentrations of blood antioxidants or urinary isoprostanes were present in hyperthyroid cats, and were reversible after radioiodine treatment. To determine whether or not antioxidant abnormalities were associated with idiosyncratic methimazole toxicosis.

Animals

Hyperthyroid cats presented for radioiodine treatment (n = 44) and healthy mature adult control cats (n = 37).

Methods

Prospective, controlled, observational study. Red blood cell glutathione (GSH), plasma ascorbate (AA), plasma free retinol (vitamin A), α‐tocopherol (vitamin E), and urinary free 8‐isoprostanes in hyperthyroid cats were compared to healthy cats and to hyperthyroid cats 2 months after treatment.

Results

Blood antioxidants were not significantly different in hyperthyroid cats (mean GSH 1.6 ± 0.3 mM; AA 12.8 ± 4.9 μM, and vitamin E, 25 ± 14 μg/mL) compared to controls (GSH 1.4 ± 0.4 mM; AA 15.0 ± 6.6 μM, and vitamin E, 25 ± 17 μg/mL). Urinary isoprostanes were increased in hyperthyroid cats (292 ± 211 pg/mg creatinine) compared to controls (169 ± 82 pg/mg; P = .006), particularly in hyperthyroid cats with a USG < 1.035. Plasma free vitamin A was higher in hyperthyroid cats (0.54 ± 0.28 μg/mL versus 0.38 ± 0.21 in controls; P = .007). Both abnormalities normalized after radioiodine treatment. No association was found between oxidative status and prior idiosyncratic methimazole toxicosis.

Conclusion and Clinical Importance

Increased urinary isoprostane could reflect reversible renal oxidative stress induced by hyperthyroidism, and this requires additional evaluation.     

Changes of Circulating Total and Free Iodothyronine in Horses After Competitive Show Jumping With Different Fence Height

The effect of exercise on circulating T₃, T_4, free (f) T₃, and fT₄ concentrations were studied before and after competitive show jumping in 24 trained jumper horses with an age range of 11–13 years and having the same level of show experience. All horses, randomly divided into three groups paired by gender, participated in three competition levels with the same circuit design over 10 fences, with five upright and five cross-pole fences .The three fence height groups were group I (n = 8), 1.10 m; group II (n = 8), 1.20 m; and group III (n = 8), 1.30 m. Repeated measures analysis of variance showed a statistically significant effect of competitive exercise on fT₃ changes in all groups, whereas the effect of competitive exercise on T₃ changes was exclusively seen in group III. Two-way repeated measures analysis of variance showed that the effect of fence height (P = .0002) and performance results were significant (P = .0486) only for T₃ changes. Performance also affected fT₃ changes (P = .0152). No significant correlation was found between total and free iodothyronines. These results suggest a dependence of T₃ and fT₃ changes on exercise-related variables and performance results and that the thyroid response is different with respect to the different exercise-related variables, such as the varying level of difficulty and performance results.     

Some Remarks on Repeatability and Heritability of the Bascule Technique in Jumping Horses

The genetic characteristics of jumping enable a correct selection program. Linear parameters of the jump were measured by video image analysis with and without the rider. Repeatability and heritability were calculated based on the statistical model using DMUAI, including effects of the year, month of training, obstacle height, horse conformation, and rider (if necessary). The highest repeatabilities were noted for the position of head and reached 0.45–0.56 for head position in comparison to withers and 0.48–0.55 in comparison to croup. Results varied between parameters with and without riders. Repeatability under rider was slightly higher, the opposite trend was observed in heritability. It seems that the relation of head to the rest of the body has higher heritability than the height of the head above the obstacle itself.     

Short-term Evaluation of Serum Amyloid A after Exercise in Clinically Healthy Horses

Serum amyloid A (SAA), the major equine acute-phase protein, is often measured after the race to investigate whether poor performances could depend on inflammation. The aim of this study was to assess whether there is an increase in concentration of SAA in serum samples collected from 12 clinically healthy Standardbred horses 1 hour after a standard race. Exercise induced an increase in red blood cells, hematocrit, and total proteins but not in SAA. However, a two- to threefold increase of SAA concentration as compared with prerace values was found in three horses. In conclusion, the concentration of SAA in most of the samples collected 1 hour after the race remains unchanged as compared with prerace samples. However, individual variability in response to exercise exists. The evaluation of SAA immediately after the race is not clinically useful.     

Effects of a Novel Dietary Supplement on Indices of Muscle Injury and Articular GAG Release in Horses

This study determined the ability of an oral nutraceutical supplement to attenuate the oxidative stress and inflammation that occurs in muscles and joints with repeated bouts of high-intensity exercise in horses. The supplement, fed daily, was comprised of whole dried mushrooms, golden flaxseed, omega-3 fatty acids, plant-based enzymes, a melon-concentrate powder, and Saccharomyces cerevisiae boulardii. Ten horses participated in a partial cross-over design, with 7 horses completing the Control trial and 7 horses completing the supplement trial. Blood and synovial fluid samples (from the intercarpal joint) were taken before, and at 1 and 24 hours after a standardized, repeated high-intensity exercise test that was performed before supplementation and on the 22nd day of supplementation. At the end of the supplement trial exercise resulted in reduced concentrations of plasma markers of oxidative stress (decreased thiobarbituric acid reactive substances, with increased total antioxidant status and increased superoxide dismutase activity); there was no effect on plasma markers of muscle injury (creatine, creatine kinase, and aspartate aminotransferase) or inflammation (PGE₂, nitric oxide). Within synovial fluid, there was a tendency for increased superoxide dismutase activity, and decreased concentration of glycosaminoglycans. It is concluded that the supplement, when fed to horses as part of the normal diet for 23 days, was associated with reduced concentrations of markers of oxidative stress and inflammation in muscle and synovial fluid.     

The Feeding Practices and Estimated Workload in a Cohort of New Zealand Competition Horses

Data on the feeding, management, and training schedules during the week before the competition were collected via a face-to-face survey of riders competing in dressage, show jumping, or eventing at 1* and 3* level competitions. Data were collected using a pro forma recording sheet, and measurements of horse height, weight, and body condition score (BCS) were also obtained. A total of 158 of 582 riders (and horses) were surveyed, providing a response rate of 27%. The mean height, weight, and median BCS of the horses were 162 ± 1 cm, 533 ± 5 kg, and 6 (interquartile range [IQR], 5–7), respectively. The majority of horses were at pasture, most (68%, 107 of 158) 24 hr/d and fed supplementary feed either once (42%, 67 of 158) or twice daily (54%, 86 of 158). The supplementary feed was predominately a commercial premix feed (90%, 142 of 157) with additional alfalfa chaff or ensiled chopped alfalfa. The horses were offered approximately 60 MJ digestible energy (DE)/d (33–86 MJ DE/d) from supplementary feed. The horses worked for a median of 6 d/wk (IQR, 5–6 d/wk) with one rest day. The median total time trained during the week was 200 minutes (135–265 minutes), which consisted of eight separate training activities. There was no difference in time spent on different activities between the disciplines. Individual training activities were 30–40 minutes, and the median number of competitions per month was 2 (IQR, 2–3). Training workload and pattern of work were similar to reports from other countries, with the exception that many riders regularly added a “hack out” after training.     

Effect of Conditioning Horses Once,Twice, or Thrice a Week with High-Intensity Intermittent Exercise on v4

Intensive short intervals of exercise are used to condition horses for racing. In this study, the effect of exercising horses one, two, or three times a week during 6 weeks using two intervals with near-maximal speed over 100 m on v₄ (speed at which, under defined conditions, the blood lactate concentration reaches 4 mmol/L) and muscle thickness (MT) of supraspinatus and extensor carpi radialis was examined. Thoroughbreds (4-5 years of age) were exercised twice at near-maximal speed over 100 m, separated by a 10-minute period at walk, on dirt track during conditioning periods (CP) of 6-week duration. This exercise was undertaken once (six horses), twice (six horses), or thrice (five horses) a week during a CP. Before, every 2 weeks during, and 2 weeks after the CP, horses were subjected to a standardized exercise test to determine their v₄. Before and after CP, the MT of the extensor carpi radialis and the supraspinatus was examined by ultrasonography. There was no differential effect of the number of weekly exercises on v₄. Pooling the data of all horses, a decrease of v₄ was found. The decrease became evident after the sixth week of conditioning. MT did not change. The results indicate that the examined exercise protocols could negatively impact racing performance of horses.     

Effects of Citrus Extract on Plasma Biochemical Indexes,Hormone Levels and Antioxidant Function of Broilers after Transport Stress

In order to study the effects of citrus extract on the plasma biochemical indexes,hormone level and antioxidant function of broilers after transport stress,a total of 360 twenty-eight-day-old fast-growing Yellow feather broilers were randomly divided into two groups (6 replicates per group,30 per replicate).The control group was fed basic diet without antibiotics,the experimental group was fed basic diet supplemented with 10 mg/kg citrus extract.At 63 days,six chickens were selected from each replicate for transport stress test for 0,2,and 4 h,respectively,and plasma sampling were conducted after transportation.The results showed that:① For glucose,cholesterol and urea nitrogen,there was a significant interaction between food treatment and transportation time (P<0.05).Compared with the control group,the contents of urea nitrogen and cholesterol in the plasma of broilers in the experimental group were significantly lower than that in the control group,and the content of glucose in the plasma of broilers in the experimental group was significantly higher than that in the control group (P<0.05).Transport stress significantly affected the content of urea nitrogen,cholesterol and glucose in the plasma of broilers in the control group,after transportation,the content of urea nitrogen and cholesterol increased significantly,while the content of glucose decreased significantly (P<0.05).② For corticosterone,triiodothyronine and thyroxine,there was significant interaction between food treatment and transport time (P<0.05).Compared with the control group,the content of corticosterone in the plasma of broilers in the experimental group was significantly lower than that in the control group,while the content of triiodothyronine and thyroxine in the experimental group was significantly higher than that in the control group (P<0.05).Transport stress significantly affected the content of corticosterone,triiodothyronine and thyroxine in the plasma of the control group,after transportation,the content of corticosterone in the plasma of the broiler significantly increased,while the content of triiodothyronine and thyroxine significantly decreased (P<0.05).③ For glutathione peroxidase,there was a significant interaction between food treatment and transportation time (P<0.05).Compared with the control group,the glutathione peroxidase activity in the plasma of broilers in the experimental group was significantly higher than that in the control group (P<0.05);Transport stress significantly affected the activity of glutathione peroxidase in the plasma of broilers in the control group.With the prolongation of transport time,the activity of glutathione peroxidase in the plasma of broilers decreased significantly (P<0.05).Therefore,transportation stress affected the metabolism level,hormone secretion and antioxidant function of Yellow feather broiler.Adding citrus extract to the diet could improve the metabolism level,regulate hormone secretion and improve antioxidant capacity,and alleviate the impact of transportation stress on Yellow feather broiler.     

柑橘提取物对肉鸡运输应激后血浆生化指标、激素水平和抗氧化功能的影响

试验旨在研究柑橘提取物对肉鸡运输应激后血浆生化指标、激素水平和抗氧化功能的影响。选取360只28日龄快大型黄羽肉鸡,随机分2组（每组6个重复,每个重复30只鸡）,对照组饲喂不含抗生素的基础日粮,试验组饲喂添加10 mg/kg柑橘提取物的基础日粮。63日龄,从每个重复选6只鸡进行运输应激试验,分别运输0、2、4 h,运输结束后翅静脉采血取样。结果表明：①对葡萄糖（GLU）、胆固醇（CHOL）和尿素氮（BUN）而言,日粮处理和运输时间存在显著交互作用（P<0.05）。与对照组相比,试验组肉鸡血浆中BUN和CHOL含量显著低于对照组,运输2和4 h,试验组肉鸡血浆中GLU含量显著高于对照组（P<0.05）;运输应激显著影响对照组肉鸡血浆中BUN、CHOL和GLU含量（P<0.05）,随着运输时间的延长,BUN和CHOL含量逐渐提高,而GLU含量逐渐降低。②对于皮质酮（CORT）、三碘甲状腺原氨酸（T₃））和甲状腺素（T₄）而言,日粮处理和运输时间存在显著交互作用（P<0.05）。与对照组相比,运输2和4 h,试验组肉鸡血浆中CORT含量显著降低,而T₃和T₄含量显著提高（P<0.05）;运输应激显著影响对照组肉鸡血浆中CORT、T₃和T₄含量,运输后,肉鸡血浆中CORT含量显著提高,而T₃和T₄含量显著降低（P<0.05）。③对于谷胱甘肽过氧化物酶（GSH-Px）而言,日粮处理和运输时间存在显著交互作用（P<0.05）。与对照组相比,试验组肉鸡血浆中GSH-Px活性显著高于对照组（P<0.05）;运输应激显著影响对照组肉鸡血浆中GSH-Px活性,随着运输时间的延长,其活性显著降低（P<0.05）。综上,运输应激影响黄羽肉鸡机体的代谢水平、激素分泌和抗氧化功能,日粮中添加柑橘提取物可改善肉鸡的代谢水平,调控激素分泌和提高抗氧化能力,缓解运输应激对黄羽肉鸡的影响。     

Preliminary Study on Age- and Sex-Dependent Alterations in the Composition of Skeletal Muscle Fibers of Brasileiro de Hipismo Horses

The aim of this work was to characterize the distribution of myofibers in the gluteus medius muscle of inactive horses of the Brasileiro de Hipismo (BH) breed at different ages by means of histochemical analyses, according to sex and depth of the biopsy. A total of 78 inactive horses (9 castrated males, 35 stallions, and 34 females) of the BH breed, aged 1 to 4 years, were used. A percutaneous muscle biopsy was obtained with a 6.0-mm Bergström-type needle, which allowed the removal of muscle fragments at depths of 20 and 60 mm. Myofiber types were determined based on myofibrillar adenosine triphosphatase (mATPase) and nicotinamide dinucleotide tetrazolium reductase (NADH-TR) techniques. Morphometry of the fibers was determined based on cross-sectional area (CSA), mean frequency (F), and relative cross-sectional area (RCSA). The current study demonstrated that BH horses 3 and 4 years of age show a greater percentage of, and area occupied by, type IIA fibers and lower percentage of type IIX fibers in the gluteus medius muscle compared with horses 1 and 2 years of age. No difference was found between sexes in the frequency of and area occupied by the different fiber types at any of the depths and ages studied. In this study, females showed a greater CSA for all fibers in comparison with males, at 1 year of age. The results of the current study indicate that the gluteus medius muscle of inactive BH horses shows modifications in its structural and biochemical composition during the growth of the animals, leading to a better oxidative capacity.     

The Effect of Different Physical Exercise on Plasma Leptin,Cortisol, and Some Energetic Parameters Concentrations in Purebred Arabian Horses

Leptin is a hormone that coordinates food intake, energy expenditure, and metabolic rate; it is, however, unknown how exercise influences plasma leptin concentration in horses. The aim of the study was to evaluate the exercise-induced changes in plasma leptin concentration in purebred Arabian horses competing in races and endurance rides. A total number of 26 horses (12 purebred Arabian racehorses aged 3–5 years and 14 endurance horses aged 7–14 years) were studied during performing routine physical exercise. From each horse, blood samples were collected at rest and immediately after the exercise session. Concentrations of plasma leptin, cortisol, lactic acid, uric acid, triacylglycerols, glycerol and free fatty acids were determined. Exercise-induced increase in cortisol and free fatty acid values were higher in endurance horses than in racehorses. Neither endurance nor race exercises influenced the plasma leptin concentration. Further research is needed to elucidate the effects of different types of exercise on leptin synthesis and secretion in horses.     

Pharmacokinetics and Effects of Alkalization after Intravenous Administration of Eltenac in Horses

Eltenac (ELT) [4-(2,6-dichlorophenyl)amino-3-thiophene] is a non-steroidal anti-inflammatory drug (NSAID) that was developed for veterinary use in horses and cattle. The pharmacokinetics of ELT was evaluated in horses at 0.5 mg/kg body weight (BW) after single IV injection after 5 days of repeated IV administration and after a single IV injection in horses previously subjected to 250 mg/kg BW of sodium bicarbonate (NaHCO₃) as an alkalization treatment. The aim was to determine whether blood and subsequent urinary alkalization could modify the pharmacokinetics of ELT. Drug quantification was performed with serum and urine using high performance liquid chromatography with UV-visible detection. The results were also integrated with cyclo-oxygenase-inhibition literature data to review the dosage scheme of ELT in horses. After a single intravenous administration, ELT was characterized by rapid distribution (mean t½_λ1 = 0.18 ± 0.07 hour) and a short elimination half-life (mean t½_λ2 = 2.9 ± 0.68 hour). The volume of distribution was small (V_dss = 253.51 ± 47.55 mL/kg), which is likely because of the high percentage of drug protein binding (approximately 97%). The AUC_0-∞ and Cl_B were 6.92 ± 0.84 h*μg/mL and 73.2 ± 10 mL/h/kg, respectively. Repeated administration did not cause either accumulation or modification of the pharmacokinetic profile. The in vitro effective concentrations were maintained for a 6-hour period. The alkalization procedure appeared to accelerate drug elimination, as ELT was quantifiable only for 6 hours; however, the drug clearance was not significantly modified. Thus, the administration of alkaline compounds to accelerate the elimination of ELT is not completely confirmed.     

Serum Concentrations of Lidocaine and Its Metabolites MEGX and GX During and After Prolonged Intravenous Infusion of Lidocaine in Horses after Colic Surgery

Lidocaine is the most commonly used prokinetic after gastrointestinal surgery in horses. Cardiovascular status, hepatic function, and duration of therapy are the primary determinants of lidocaine metabolism, and these factors could affect equine patients after colic surgery. This study examined the systemic concentrations of lidocaine and its active metabolites monoethylglycinexylidide (MEGX) and glycinexylidide (GX), in horses that had undergone colic surgery and subsequently received prolonged postoperative lidocaine infusions. The mean lidocaine concentration increased over the course of treatment but did not exceed the therapeutic range. Concentrations of MEGX and GX increased progressively, and concentrations exceeding 1,000 ng/ml were observed frequently after 72 hours of infusion. None of the horses in the study developed severe signs of toxicity; however, the progressively increasing concentrations of lidocaine, MEGX, and GX are cause for concern in clinically ill patients receiving prolonged lidocaine therapy. The potential contribution of MEGX and GX should be considered when evaluating adverse reactions to prolonged lidocaine infusions.     

The Biomechanics of Movement of Horses Engaged in Jumping Over Different Obstacles in Competition and Training

There exist numerous scientific studies, which are evaluating the biomechanics of the jumping movement of horse and rider over different types of obstacles. The most important results of the kinematic and kinetic investigations are the takeoff position, the acceleration of the hind limbs at takeoff as well as the load of the fore limbs at landing. The starting position directly before takeoff is described by the angle of the trunk, the associated height of the center of gravity (CG), and by the distances of the hind limbs to the obstacle. The acceleration of the hind limbs at takeoff, which is expressed by the vertical and horizontal velocity of takeoff at CG, is a further important indicator for a successful overcoming of a given obstacle. Based on the landing, the load bearing of the fore limbs is an important factor with regard to a long-term health maintenance of horses tendons. From methodological point of view, the majority of investigations use a variety of visual methods in two dimensions. Occasionally, accelerometers and force plates were used to get further information. A combination of visual methods and accelerometer seems to be promising.     

Selected Biochemical Indicators of Equine Rhabdomyolysis in Arabian Horses: Acute Phase Proteins and Trace Elements

Although creatine kinase (CK), aspartate transaminase (AST), cytokines, and oxidative stress parameters were shown to be useful biomarkers for diagnosis of equine rhabdomyolysis, additional biomarkers of the disease may be of interest to indicate prognosis of the disease. Therefore, the present study investigated acute phase proteins and trace elements as additional biomarkers of ER. Sixty male horses (4-6 years old) of 2 equal groups were used. Horses of the first group were clinically healthy and served as a control group, whereas horses of the second group were ER-diseased animals. Harvested sera were used for estimation of the activities of CK, AST, lactate dehydrogenase (LDH), serum amyloid A (SAA), haptoglobin (Hp), ceruloplasmin (Cp), copper, iron, and zinc, whereas plasma samples were used for determination of fibrinogen. The present findings revealed a significant (P ≤ .05) increase in values of CK, AST, and LDH in diseased horses compared to those in control values. In addition, a significant (P ≤ .05) increase in SAA (162.6 ± 5.32 mg/L), Hp (3.6 ± 0.54 g/L), Cp (39.32 ± 2.31 mg/L), and copper (28.36 ± 1.23 μmol/L) along with a significant (P ≤ .05) reduction in levels of iron (9.32 ± 0.23 μmol/L) and zinc (8.65 ± 1.02 μmol/L) was recorded in diseased horses compare to that in controls (11.3 ± 2.2 mg/L, 0.8 ± 0.2 g/L, 24.23 ± 1.32 mg/L, 18.41 ± 1.03 μmol/L, and 14.2 ± 0.42 μmol/L, respectively). In conclusion, SAA, Hp, Cp, copper, and zinc were useful prognostic biomarkers for the diagnosis of ER in Arabian horses.     

Comparison of Serum Amyloid A in Horses With Infectious and Noninfectious Respiratory Diseases

The acute phase protein serum amyloid A (SAA) has been shown to be a useful inflammatory parameter in the horse, but studies showing SAA responses to specific respiratory disease etiologies are limited. The goal of this study was to evaluate SAA responses in horses with infectious and noninfectious respiratory diseases as well as healthy, control horses. Two hundred seven horses were grouped into the following categories: equine influenza virus (EIV), equine herpesvirus-4 (EHV-4), Streptococcus equi subspecies equi (S. equi ss equi), inflammatory airway disease (IAD), and healthy controls. Serum amyloid A concentrations were determined for all horses on serum using a stall-side lateral flow immunoassay test. Serum amyloid A levels were found to be significantly greater for infectious respiratory diseases (EIV, EHV-4, S. equi ss equi) and horses with IAD when compared to control horses. There was a significant difference between viral and bacterial infections and IAD. Although SAA values from horses with S. equi ss equi were significantly greater when compared to horses with viral infections (EIV/EHV-4), the wide range of SAA values precluded accurate classification of the infectious cases. In conclusion, SAA is more reliably elevated with infections of the respiratory tract rather than noninfectious airway conditions. This can facilitate early detection of respiratory infections, help track disease progression, and aid practitioners in making recommendations about proper biosecurity and isolation of potentially contagious horses.     

Oxidative Stress Associated With Spasmodic,Flatulent, and Impaction Colic in Draft Horses

The aim of the present study was to evaluate the oxidative stress level and antioxidant trace elements status associated with spasmodic, flatulent, and impaction colic in draft horses. For this purpose, venous blood samples were obtained from 20 randomly selected clinically healthy draft horses (control group) and 60 draft horses with different types of colic (spasmodic colic, n = 20; flatulent colic, n = 20; and impaction colic, n = 20). In horses with flatulent and impaction colic, there was a significant (P < .05) decrease in the total antioxidant capacity and activity of reduced glutathione (GSH) and catalase (CAT) as well as level of selenium, copper, zinc, and iron. However, there was a significant (P < .05) increase in the activity of superoxide dismutase (SOD) and in the level of malondialdehyde (MDA), interleukin-6 (IL-6), and manganese. Meanwhile, glutathione reductase (GR) was significantly (P < .05) increased in flatulent colic and significantly (P < .05) decreased in impaction colic. The oxidative stress index (OSI) was significantly (P < .05) increased in horses with flatulent and impaction colic. In horses with flatulent colic, there was a negative correlation between CAT and SOD (r = −0.446), MDA and zinc (r = −0.450), and IL-6 and zinc (r = −0.470). However, those with impaction colic, a negative correlation was recorded between CAT and MDA (r = −0.602), copper and GSH (r = −0.474), iron and GR (r = −0.511), and OSI and GR (r = −0.662). The results of the present study indicate that oxidative stress, with alteration of antioxidant trace element levels, is a feature of flatulent and impaction colic in draft horses.     

Changes of sires in a breeding farm enables maintenance of DNA‐level genetic variation in a produced herd of Hokkaido Native Horses

We investigated whether regular changes of the sire in a breeding farm of Hokkaido Native Horses (HKDs) enables the DNA‐level genetic variation of the produced animals to be maintained. The genotypes of 31 microsatellite markers were identified and analyzed in 207 animals produced in a breeding farm in which the sire was replaced every 3 to 5 years. The mean allele number indicating the degree of genetic variation was 5.97 and was similar to those reported previously. The mean observed heterozygosity was 0.74 and was higher than the expected heterozygosity, 0.69; F_IS was ?0.07, indicating that the analyzed animals reflected frequent outbreeding and had maintained genetic variation. Based on genetic structural analysis, the number of genetic subpopulations of the animals was estimated to be as 6, and the majority (more than 50%) of each subpopulation corresponded to the progeny of one of the sires used in the breeding farm; these observations suggested that genetic variation in the analyzed animals reflected the genetic differences among sires. Pedigree records indicated that the average co‐ancestry coefficient between sires used in the breeding farm was 0.015 corresponding to second cousin. This level of kinship among sires is acceptable for producing HKDs that maintain genetic variation.