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The Peruvian Paso Horse is considered one of the best saddle horses worldwide due to the gait that makes this horse perform one of the smoothest walks. The overreach, term, and acuteness are the most characteristic movements in the gait, making them the most desirable attributes in its breeding and reproduction. Repeatability of overreach, term, and acuteness in Peruvian Paso horses (PPH) have not been determined to date. It is important to estimate this parameter for application in PPH breeding, therefore, the aim of this study was to estimate the repeatability of overreach, term, and acuteness of PPHs. The study included records of 137 stallions and mares. All measurements were recorded in MP4 video format with a resolution of 1920 x 1080 megapixels and at 60 frames per second. All traits were measured three times (once per stride), and each trait was analyzed. KINOVEA software version 0.9.5 was used to analyze the measurements. A multivariate repeated measures animal model with sex effect was used to estimate the variance components for each trait using WOMBAT software. Repeatability was high in all traits (> 0.78; Table 1). The low standard error values close to 0.02 indicate high precision in all traits (0.904, 0.855, and 0.903 for overreach, term, and acuteness, respectively), being defined as the variance of the mean of “n” measurements as a percentage of the variance of one measurement, indicating that this parameter has little effect on the temporal environment of the three traits. These results demonstrate that previous training can influence the regularity of the gait, in agreement with the present study, in which only adult animals that have already had previous training were evaluated. Furthermore, our results corroborate that traits with high repeatability require few measurements (3 in this study) to obtain greater precision, and an increase in the number of measurements may be irrelevant for parameter estimation. In a breeding plan, this high precision may be due to an increase in the additive genetic variance, indicating that two or more measurements have greater heritability than a single measurement, allowing a better breeding value estimate to be obtained. Considering the high repeatability values found, this parameter can be used as an indicator of how effective the selection process can be, considering its relationship with heritability, as repeatability values are higher than heritability, due to the inclusion of permanent environmental variance (within-individual variance) in its estimation. High values also indicate that individuals tend to have consistent performance, and therefore, obtaining several measures for evaluation may be impractical. It can be concluded that overreach, term, and acuteness have high repeatability values, which allows these traits to respond better in a selection process and performance evaluation for subsequent competitions. [ABSTRACT FROM AUTHOR]

While beneficial in rehabilitation, aquatic exercise effects on cartilage and bone metabolism in young, healthy horses has not been well described. Therefore, 30 Quarter Horse yearlings (343 ± 28 kg; 496 ± 12 d of age) were stratified by age, body weight (BW), and sex and randomly assigned to 1 of 3 treatments for 140-d to evaluate effects of aquatic, dry, or no exercise on bone and cartilage metabolism in young horses transitioning to an advanced workload. Treatments included nonexercise control (CON; n = 10), dry treadmill (DRY; n = 10), or aquatic treadmill exercise (H2O; n = 10; water: 60% wither height, WH). Horses were housed individually (3.6 × 3.6 m) from 0600 to 1800 hours, allowed turnout (74 × 70 m) from 1800 to 0600 hours, and fed to meet or exceed requirements. During phase I (days 0 to 112), DRY and H2O walked on treadmills 30 min/d, 5 d/wk. Phase II (days 113 to 140) transitioned to an advanced workload 5 d/wk. Every 14-d, WH, hip height (HH), and BW were recorded. Left third metacarpal radiographs on days 0, 112, and 140 were analyzed for radiographic bone aluminum equivalence (RBAE). Every 28-d, serum samples were analyzed for osteocalcin and C-telopeptide crosslaps of type I collagen (CTX-1), and synovial fluid samples were analyzed for prostaglandin E2, collagenase cleavage neopeptide (C2C), collagenase of type I and type II collagen, and carboxypeptide of type II collagen using ELISAs. All data were analyzed using PROC MIXED of SAS, including random effect of horse within treatment, and repeated effect of day. Baseline treatment differences were accounted for using a covariate. There were treatment × day interactions (P < 0.01) where OC and CTX-1 remained consistent in both exercise groups while inconsistently increasing in CON. There were no treatment differences (P > 0.30) in RBAE, BW, or HH, but all increased over time (P < 0.01). There were no treatment × day interactions of synovial inflammation or markers of cartilage metabolism; however, there was an effect of day for each marker (P <0.03). Changes in biomarkers of cartilage turnover in horses exercised at the walk, whether dry or aquatic, could not be distinguished from horses with access to turnout alone. This study indicates that early forced exercise supports consistent bone metabolism necessary for uniform growth and bone development, and that there are no negative effects of buoyancy on cartilage metabolism in yearlings transitioned from aquatic exercise to a 28-d advanced workload. [ABSTRACT FROM AUTHOR]

Cannabidiol (CBD) has become a popular product in the recent months due to change in legislation with the passing of the Agricultural Improvement Act in 2018. Cannabidiol comes from the plant Cannabis sativa L. and binds to cannabinoid receptors throughout the endocannabinoid system. These receptors are located throughout the body and are prominent in the brain and reproduction tract. Although the effects of CBD on physiology have been researched, little data on the behavioral effects exist, even less so in horses. Calming supplements that may negate aggressive stallion behavior are not suitable due to potential soporific effects that can affect libido. In addition to the effectiveness of CBD to modify behavior in horses, it is also unclear if CBD influences stallion libido. The objective of this study was to evaluate sexual behavior in stallions given a daily CBD supplement for 70 days. Two-year old stallions (n = 8) were assigned to either a Control (CON; n = 3) or Cannabidiol (CBD; n = 4) treatment groups. Cannabidiol was administered at a rate of 0.6 mg/kg BW daily, and equal volume of olive oil was given as a placebo to CON. Horses were weighed every Monday at which time dosages were recalculated to adjust for body weight changes. Behavior data collection occurred twice per week during semen collections. Video data were recorded by placing two cameras, one placed in view of the tease area, and one placed in view of the mount, for behavior data backup. Behavioral data was tallied by handlers calmly calling each behavior as it occurred during collection. The behaviors collected included Flehman's response, bites, strikes, mounts, high pitch vocalizations, and low pitch vocalizations. Data were analyzed using a Chi Square Test within R Statistical Program (R Core Team). Results were considered significant at P < 0.05. Throughout the duration of the study, all stallions exhibited normal sexual behavior, regardless of treatment. Results showed that total low and high pitch vocalizations, bites, and Flehman's were affected by treatment (P < 0.01). Cannabidiol-treated stallions had more low pitches (60), compared to CON (58). Cannabidioltreated stallions had fewer bites (145) compared to the CON (146). Cannibidiol stallions displayed Flehman's more frequently (270) than CON (236). Flehman's response and bites were lower for stallions on cannabidiol in Week 1 but increased by Week 10 (P < 0.01), while only Flehman's response increased in the CON group over time (P < 0.01). These findings indicate that CBD may influence breeding behavior in young stallions specifically when supplemented over time. Further research should focus on the impact of CBD on breeding behaviors in mature stallions and the longevity of the behavioral response to CBD. [ABSTRACT FROM AUTHOR]

Eight cecally cannulated Quarter Horses were used in a replicated 4 × 4 Latin square experiment conducted in four 14-d periods to determine effects of sodium caseinate (casein) on hindgut fermentation and fiber digestion. During each period, horses were assigned to one of four treatments consisting of control (water; CON), 0.125 g casein/kg BW (LOW), 0.25 g casein/kg BW (MED), or 0.5 g casein/kg BW (HI). Casein was solubilized in 800 mL water and dosed directly into the cecum at 0700 and 1900 hours using a metal dosing syringe. Smooth Bromegrass hay (CP 8.50%), water, and salt were provided ad libitum. New hay was fed at 0700 and 1900 hours, and orts were recorded at 1900 daily. During the final 3 d of each period, cecal digesta were collected every 6 h, pH was measured, and samples were frozen for subsequent analyses of VFA and NH3 concentrations. Feed intake during the final 4 d of each period was recorded. Feces were collected during the 3-d sampling period, pooled, subsampled, and frozen. Fecal samples were analyzed for pH and used to determine digestibilities of DM, OM, NDF, and ADF. Statistical analyses were performed via the GLIMMIX procedure of SAS 9.4. Linear and quadratic effects of sodium caseinate on pH, VFA concentrations, and apparent digestibility were assessed by SAS. Digestibilities of DM, OM, ADF, and NDF were unaffected by treatment (P > 0.40). Horses dosed with CON and MED treatments had greater cecal pH than those fed LOW or HI treatments (P < 0.01). Cecal NH3 concentrations increased linearly in response to the amount of casein administered (P < 0.01). Cecal NH3 decreased 6 h after dosing and addition of new hay, regardless of treatment (P < 0.01). Total cecal VFA were unaffected by treatment (P > 0.10), but VFA changed over time with the greatest concentrations observed 6 h after treatments were administered and introduction of new hay (P < 0.01). Treatment did not affect DMI (P ≥ 0.17). In this experiment, cecal infusions of sodium caseinate had minimal to no effect on fermentation parameters or fiber degradation in the horse. A type II error may have occurred due to small population size or the medium quality hay fed to these horses provided sufficient N for microbial fermentation. [ABSTRACT FROM AUTHOR]

The main purpose of the study was to establish gender differences and reference intervals for the concentration of chemical elements in hair from the mane of horses bred in a biogeochemical province, the South Urals of Russia. The studies were carried out on physiologically healthy stallions and mares of the Bashkir breed (n=120; age 3-7 years). Hair samples were taken from the manes of horses. The elemental composition of samples was estimated from 13 chemical elements (Al, Cd, Co, Cr, Cu, Fe, I, Mn, Pb, Se, Sr, Zn, Si) by ICP AES and ICP MS. Reference intervals for the content of chemical elements in animal hair were calculated in accordance with the recommendations of Poulsen et al. (1997; 2.5-97.5 percentile). It was found that the concentrations of Al, Co, Fe and Pb in the hair of stallions significantly (P≤0.05) exceeded those of mares. The content of Zn, on the contrary, was greater in stallions than in mares. Due to the fact that the elemental composition of the hair of stallions and mares was significantly different, the reference intervals were calculated for each gender group separately. For mares, these values were (mg/kg): Al (41.14-186); CD (0.0049-0.0189); Co (0.039-0.138); Cr (0.389-1.97); Cu (4.66-6.61); Fe(70.99-263); I (0.161-0.333); Mn (2.7-7.66); Pb (0.078-0.265); Se (0.129-0.292); Si (7.88-16.93); Sr (1.53-4.5); Zn(118-156); for stallions: Al (121-226); CD (0.0053-0.0125); Co (0.073-0.187); Cr (0.362-0.887); Cu (5.18-7.01); Fe (210-338); I (0.128-0.502); Mn (2.43-9.15); Pb (0.234-0.928); Se (0.168-0.356); Si (5.25-13.13); Sr (2.44-3.8); Zn (147-193). It is proposed to use the obtained values as physiological standards for assessing the elemental status of the Bashkir horses bred in the South Ural biogeochemical province. [ABSTRACT FROM AUTHOR]

Nine pregnant mares (18.2 ± 0.7 y; 493.82 ± 13 kg BW) were used to test the hypothesis that dietary supplementation of arginine would enhance placental vascularity and nutrient transport throughout gestation in aged mares. Mares were balanced by age, BW, and stallion pairing, and randomly assigned to one of two dietary treatments consisting of supplemental L-arginine (50 mg/kg BW; n=5) or L-alanine (100 mg/kg BW; n=4; isonitrogenous control). Mares were individually fed concentrate top-dressed with the respective amino acid treatment plus ad libitum access to Coastal bermudagrass hay. Treatments began on d 14 of gestation and were terminated at parturition. Mare BW, BCS, and rump fat were determined every 28 d and concentrate adjusted accordingly. Parturition was attended with foaling variables and placental measures recorded. Placental tissue from the pregnant horn underwent histological analyses to assess cell-specific localization of vascular endothelial growth factor (VEGF) and cationic amino acid transporter 1 (CAT1) proteins. Semiquantitative analyses were performed using 10 non-overlapping images per sample fixed in a 10X field (Fiji ImageJ v1.2). Data were analyzed using SAS PROC MIXED procedure. BW increased (P < 0.01) in all mares with advancing gestation. BW, BCS, and gestation length of mares were not influenced (P > 0.05) by supplemental arginine. Compared with argininesupplemented mares, control mares had a thicker rump fat layer (P < 0.01) at parturition. Body length, height, and BW of foals at birth, as well as placental weight, volume, and positive staining for VEGF and CAT1 at parturition were not affected (P > 0.05) by maternal arginine supplementation. These results indicate dietary arginine supplementation (50 mg/kg BW) is safe for gestating mares and promotes mobilization of white adipose tissue. A larger number of mares is required to determine effects of supplemental arginine on embryonic/fetal survival and growth in mares. [ABSTRACT FROM AUTHOR]

Genomic evaluations often use as pseudo-phenotypes corrected means of progeny performances, like daughter yield deviations (DYD) in dairy species. In horse breeding, own performances are also available and performances from other relatives (as half sibs) may play an important part in the EBV because the number of progeny remains low, even for stallions. The first step for genomic selection in horses is therefore to generate pseudo-phenotypes for genomic analysis when parental or own information is considered. This work presents an easy method to compute deregressed EBV from regular pedigree-based genetic evaluations (EBV, reliabilities) to be used in genomic evaluations. The proposed methodology builds deregressed proofs so that they combine own performances (from genotyped individuals) and performances of relatives (outside of the genotyped sample). An application to show jumping horse data is presented. A sample of 908 stallions specialized in show jumping [71% Selle Français (SF), 17% foreign sport horses (FH), 13% Anglo Arab (AA)] were genotyped. Genotyping was performed using the Illumina Equine SNP50 BeadChip, and after quality tests, 44,444 SNP were retained. Two methods were used for genomic evaluation: GBLUP and BayesCit, and 6 validation data sets were compared, chosen according to breeds SF + FH + AA or SF + FH, family structure (more than 3 half sibs), reliability of sires (>0.97) or sons (>0.72). In spite of a favorable genetic structure [linkage disequilibrium equal to 0.24 at 50 kb pairs], results showed low advantage of genomic evaluation. On the validation sample SF + FH + AA, the correlation between deregressed proofs and GBLUP or BayesC-rt predictions was 0.39, 0.37, 0.51 according to the different validation data sets, compared with 0.36, 0.33,0.53 obtained with BLUPpredictions. Correlations were much lower on the SF + FH sample. Research is pursued to understand this low advantage of genomic selection and to improve the methodology for genomic evaluation in this context, which is less favorable than dairy cattle breeding. [ABSTRACT FROM AUTHOR]

Stallions (n = 8) were implanted with a thermal sensory device in the muscle of the neck and the subcutaneous tissue of the scrotum and then assigned to either a nonexercise (Non-EX; n = 4) or exercise (EX; n = 4) group. A motorized equine exerciser was used to work EX stallions 30 min/d for 4 d/wk during a 12-wk period from July through October 2010. Temperatures (subcutaneous scrotal, intramuscular neck, and rectal) were recorded at 0, 22, and 30 min after the start of exercise, as well as 60 and 120 min post-exercise. Hourly ambient temperature and relative humidity data were also obtained. Semen was collected at 0,4, 8, and 12 wk and analyzed for volume, sperm concentration, total sperm numbers, percentages of total and progressively motile sperm, sperm morphologic characteristics, and sperm DNA quality. No effect (P > 0.05) of exercise was observed on any of the measured semen variables. Implantation of thermal sensory devices had no demonstrable acute or chronic effects on the scrotal or neck tissue, indicating that the thermal sensory devices are a safe and effective way to measure subcutaneous scrotal and neck temperatures. At 22 and 30 min of exercise, rectal and neck temperatures increased (P < 0.0001) approximately 1.9 and 2.4°C, respectively, and scrotal temperatures simultaneously increased, although not significantly (P = 0.33), approximately 0.8°C. Correlations existed between scrotal, neck, rectal, and ambient temperatures, with the correlation between scrotal and rectal temperatures being greatest (rs = 0.76; P < 0.0001). Although moderate exercise for a short duration in extreme heat and humidity did significantly increase core body temperatures in stallions, scrotal temperatures did not significantly increase, and sperm parameters were unaffected. [ABSTRACT FROM AUTHOR]

This study was conducted to estimate the nutritional value of diets given to stallions of different breeds during the reproductive season, and comparing allowances with requirements. The systems compared were the French INRA, the 1989 NRC, and the 2007 NRC. Data on reproductive activity, daily exercise, BW, BCS, feed intake, and feed composition during 4 mo (from March to June) were recorded on 12 stallions used for commercial AI programs. Stallions belonged to 3 different breeds: Italian Haflinger (IH, n = 4), Holstein (HOL, n = 4), and Italian Heavy Draft horse (IHDH, n = 4). Data recorded were used to estimate the actual energy and protein intakes and theoretical requirements of the stallions using the aforementioned systems. A deviation index [DI = (intake - requirement)/intake × -1] was calculated to allow a comparison among methods as a proportion of under- or overestimates of theoretical requirements. All data were statistically analyzed with a mixed model for repeated measurements. The reproductive activity of the stallions was affected by month (less in March and greater in subsequent months; P < 0.05). Daily exercise was generally low during the middle breeding season, and the intensity and kinds of exercise differed according to the breeds. Changes of BW and BCS of the stallions were not statistically significant (P = 0.69 and P = 0.17, respectively) during the experimental period, and therefore diets could be considered balanced to support all animal needs. However, the energy and protein allowances were not always consistent with the theoretical requirements considering all 3 nutritional systems. Energy and protein INRA recommendations showed, on average, +0.90 and +0.27 greater DI than actual intakes, respectively, for IH and HOL stallions, whereas the theoretical requirements were much closer to allowances for the IHDH stallions (DI close to 0). The 1989 NRC energy and protein recommendations, respectively, were +0.67 and +0.87 greater than intake for IH, +0.28 and +0.43 greater for HOL, and only +0.06 and +0.17 greater for IHDH stallions. The 2007 NRC energy and protein recommendations, respectively, were +0.70 and +0.52 greater for IH, +0.33 and +0.17 greater for HOL, and +0.52 and +0.49 greater for IHDH than actual intakes. Therefore, all systems overestimated the requirements of the stallion, particularly in lighter breeds. Further studies to validate requirements for breeding stallions of different sizes are recommended. [ABSTRACT FROM AUTHOR]

The velocity at which blood lactate concentration ([LA]) of 4 mmol/L is reached (v4) is widely used to determine fitness, but there are few published data on using [LA] as a guide for the exercise speed for training in horses. In this study, the effect of 3 conditioning programs with [LA] guided exercise speeds on v4, v200 (speed at a heart rate of 200 beats/mm), blood [LA], plasma FFA ([FFA]), and alanine concentrations ([alaninel), before and after exercise, as well as heart rate during exercise, of horses was examined. Six 2-yr-old Haflinger stallions underwent an initial treadmill-based standard exercise test (SET). A regression analysis [LA]-speed relationship was used to calculate v15, v25, and v4. Horses were then randomly assigned to 1 of 3 conditioning programs according to a 3 x 6 Latin square design. During 6 wk, horses exercised on the treadmill every other day for 45 mm at their calculated v1.5 or v2.5 or 25 mill at their v4. Each conditioning period (CDP) was followed by 5 wk without conditioning. At 2 and 9 d, and 5 wk, after the end of the CDP, the horses performed another SET to evaluate again the v4 and v200. Blood [LA], plasma [FFA], and [alanine] were measured before and after heart rate during exercise sessions 1, 11, and 21 in each CDP. None of the exercise programs had an effect on v4 and v200 (P > 0.05). The increase of the mean [LA] after exercise decreased during CDP (P < 0.05), and the increase of mean heart rate during exercise tended to decrease as well (P = 0.07). There was no difference among the conditioning programs. Plasma [FFA] before exercise was not influenced by the CDP (F> 0.05). The plasma [FFA] was always greater after exercise (P < 0.05), but there was no difference among conditioning programs. Overall, the increase was greatest after the 21st exercise session compared with the 1st and 11th exercise sessions (P < 0.05). The mean plasma [alanine] before exercise remained similar during all CDP (P > 0.05). Mean plasma [alanine] of the horses was increased after all exercise sessions measured (P < 0.05). There was no difference among conditioning programs (P> 0.05). It is concluded that conditioning with the exercise types used had small effects. This could have been because the exercise stress was too small, but also because the workload was not increased during the CDP. [ABSTRACT FROM AUTHOR]

ABSTRACT: The mating policy for Spanish Purebred horses encourages the same or closely related stallions to be used for reproduction across studs differing in environments. Stallions may perform differently across studs, and if so, adjustment for the sire x stud (ss) interaction is recommended. However, there are no studies available that analyzed the influence of ss interaction on estimation of genetic parameters in horses. This research is aimed at assessing the implications of including ss interaction in models fitted for the estimation of genetic parameters for traits under selection using 8 body measurements in Spanish Purebred (Andalusian) horses: height at withers, height at chest, leg length, body length, width of chest, heart girth circumference, knee perimeter, and cannon bone circumference. Body measurements were available for 11,894 horses. Genetic parameters and EBV were estimated using animal models by REML. The inclusion of the ss interaction gives reduced estimates of heritability. Generally, the genetic correlations estimated using the models including the ss interaction were greater than those obtained using the simpler model. Estimates for the ss variance as a proportion of the total plienotypic variance ranged from 0.02 (height at withers) to 0.11 (width of chest). Estimates between the ss interaction correlations associated with each body measurement were positive, significant, and from moderate to low. The range of EBV estimated using the model including the ss interaction decreased with respect to those estimated using the simpler model, and the EBV ranking order was affected. The models including ss interaction fitted significantly better. Therefore, the genetic parameters estimated using the ss interaction may be more realistic, and the obtained (co)variances may be assumed to be closer to the true population parameters. This interaction may result from selective decisions or preferential management practices causing greater similarity between the progeny of a sire in the same stud. It is therefore advisable to include it in genetic models used in horse breeding schemes. [ABSTRACT FROM AUTHOR]

Osteochondrosis (OC) is an important orthopedic developmental disorder in many horse populations. A review of the literature revealed widely variable heritability estimates for the disorder. We estimated the genetic variables (heritabilities and genetic correlations) of various manifestations of OC. Femoropatellar, tarsocrural, and metacarpophalangeal and metatarsophalangeal joints of 811 randomly selected yearlings from the Royal Warmblood Studbook of the Netherlands descending from 32 representative stallions, were scored for OC at 28 predilection sites. At each site, OC was scored in 5 categories, distinguishing between flattened bone contours and fragments. At the animal level, the overall heritability of OC was 0.23, the heritability of flattened bone contours was 0.08, and the heritability of fragments was 0.22. At the joint level, heritability was greatest in the tarsocrural joints, intermediate in the metacarpophalangeal and metatarsophalangeal joints, and least in the femoropatellar joints. The heritability estimates for the coritralateral joint homologs were very similar. The genetic correlation between the tarsocrural arid femoropatellar joint was strong, whereas correlations between the metacarpophalangeal and metatarsophalangeal and other joints were moderate. The genetic correlation between flattened bone contours and fragments at the animal level was 0.80. Scoring OC on a 5-point categorical scale resulted in greater heritability on the observed scale than when analyzing OC as a binary trait. Our results suggest that selection against OC could best be performed by taking into account the OC status of all 4 joints, the femoropatellar, the tarsocrural, and the metacarpophalangeal and metatarsophalangeal joints, and discerning between flattened bone contours and fragments. [ABSTRACT FROM AUTHOR]

Three experiments tested the hypotheses that daily cortisol rhythm, feeding time, and/or insulin infusion affect(s) leptin secretion in stallions. Ten mature stallions received ad libitum hay and water and were fed a grain concentrate once daily at 0700. In Exp. 1, stallions received either a single injection of dexamethasone (125 ,μg/kg BW i.m.; n = 5) or vehicle (controls; n = 5) at 0700 on d -1. Starting 24 h later, blood samples were collected every 2 h for 36 h via jugular venipuncture. Cortisol in control stallions varied (P < 0.01) with time, with a morning peak and evening nadir; dexamethasone suppressed (P < 0.01) cortisol concentrations. Leptin and insulin were greater (P < 0.01) in the treated stallions, as was the insulin response to feeding (P < 0.01). Leptin in control stallions varied (P < 0.01) in a diurnal pattern, peaking approximately 10 h after onset of eating. This pattern of leptin secretion was similar, although of greater magnitude (P < 0.01), in treated stallions. In Exp. 2, five stallions were fed the concentrate portion of their diet daily at 0700 and five were switched to feeding at 1900. After 14 d on these regimens, blood samples were collected every 4 h for 48 h and then twice daily for 5 d. Cortisol varied diurnally (P = 0.02) and was not altered (P = 0.21) by feeding time. Insulin and leptin increased (P < 0.01) after feeding, and the peaks in insulin and leptin were shifted 12 h by feeding at 1900. In Exp. 3, six stallions were used in two 3 x 3 Latin square experiments. Treatments were 1) normal daily meal at 0700; 2) no feed for 24 h; and 3) no feed and a bolus injection of insulin (0.4 mIU/kg BW i.v.) followed by infusion of insulin (1.2 mIU·kg BW-1mir·-1) for 180 mm, which was gradually decreased to 0 by 240 mm; sufficient glucose was infused to maintain euglycemia. Plasma insulin increased (P < 0.01) in stallions when they were meal-fed (to approximately 150 μIU/mL) or infused with insulin and glucose (to approximately 75 μIU/mL), but insulin remained low (10 μIU/mL or less) when they were not fed. The increases in insulin were paralleled by gradual increases (P < 0.01) in leptin concentrations 3 to 4 h later in stallions fed or infused with insulin and glucose. When stallions were not fed, leptin concentrations remained low. These results demonstrate that feeding time, and more specifically the insulin increase associated with a meal, not cortisol rhythm, drives the postprandial increase in plasma leptin concentrations in horses. [ABSTRACT FROM AUTHOR]

The ability to ship cooled stallion sperm for subsequent freezing at a facility specializing in cryopreservation would be beneficial to the equine industry. Stallion sperm has been centrifuged, cooled to 5°C for 12 h, and frozen without a detrimental effect on motility in a previous study; however, no fertility data were available. Experiment I compared the post-thaw motility of sperm cooled for 18 h at 15 or 5°C at either 400 or 200 × 106 sperm/mL and then frozen. Storage temperature, sperm concentration, or the interaction of temperature and concentration had no effect on total (TM) and progressive motility (PM) after cooling. Post-thaw TM and PM were higher for control than (P < 0.05) for treated samples. There was no difference in post-thaw TM and PM due to temperature or concentration. Experiment 2 further evaluated procedures for cooling before freezing. Ejaculates were either cooled to 5°C for 18 h and centrifuged, centrifuged at room temperature and then cooled to 5°C for 18 h before freezing, or centrifuged and frozen immediately (control). There was no difference among treatments on post-thaw TM or PM. In Exp. 3, mares were inseminated with semen that had been extended in skim milk-egg yolk without glycerol, centrifuged, resuspended at 200 × 106 sperm/mL, cooled to 5°C for 18 h, and then frozen or not cooled for 18 h before freezing (control). Pregnancy rates did not differ for mares receiving semen cooled and then frozen (21 of 30, 70%) or semen frozen directly without prior cooling (16 of 30, 53%). In summary, a procedure was developed for cooling stallion sperm for 18 h before freezing without a resultant decrease in fertility. [ABSTRACT FROM AUTHOR]

Experiments were conducted to study effects of macromolecules on stallion sperm capacitation and fertilization as determined by penetration of bovine zona-free and equine partially zona-removed oocytes. Stallion sperm were capacitated in TYH medium (modified Krebs-Ringer bicarbonate) supplemented with either 1 mg/mL of polyvinylalcohol (PVA) or 4 mg/ mL of BSA. Capacitation was induced with 8 bromoadenosine cyclic monophosphate (8BrcAMP; 0.5 mM) alone or in combination with 0.1 µM of ionomycin. Intraspecies gametes were co-incubated in TYH/PVA or TYH/ BSA for 18 to 20 h. For zona-free bovine oocytes, penetration rate (35%) with the combination of 8BrcAMP and ionomycin in PVA-containing medium was higher (P < 0.05) than any treatment in BSA-containing medium (5 to 6%). A similar study was conducted using equine oocytes with partially removed zonae. Sperm capacitated and used for in vitro fertilization (IVF) in PVA-containing medium had higher penetration rates (P < 0.01) than sperm in BSA-containing medium (54 vs. 11%). The effect of equine preovulatory follicular fluid on bovine oocyte penetration was assessed. Bovine oocytes were matured in tissue culture medium-199 with 0, 20, 50, or 100% equine preovulatory follicular fluid, and 1 IU/mL of equine chorionic gonadotropin. Stallion sperm were treated with 8BrcAMP + ionomycin in PVA- or BSA-containing media. The penetration rates of bovine zona-free oocytes by stallion sperm were again higher with PVA (47%) than BSA (18%; P < 0.01). Penetration rates of oocytes matured in 100% follicular fluid were higher (P < 0.05) than for oocytes matured with 0% follicular fluid. The effects of equine follicular fluid and PVA/BSA during sperm capacitation on standard bovine IVF were examined. Culture of bovine oocytes with equine follicular fluid did not affect oocyte maturation or penetration rates after IVF. Bovine sperm capacitated with heparin in PVA-containing medium yielded lower (P < 0.05) fertilization rates... [ABSTRACT FROM AUTHOR]

Determines if pyruvate, alone or in combination with xanthurenic acid, can maintain the function of equine spermatozoa after storage for 24 or 48 at five degrees Celsius. Analysis of spermatozoa; Contents of a mammalian sperm; Effects of adding pyruvate to stallion spermatozoa.

The aim of this work was to study the activity of cathepsins B, L and H in the seminal plasma of stallions with normal (>25%, n = 11) and low (< 25%, n = 13) percentage of viable sperm after freezingthawing. Sperm of 24 Arabian stallions aged from 5 to 20 years (12.1 ± 4.8 years on average) was collected during the breeding season (February-May). The activity of cathepsins in spermoplasm was studied by the spectrofluorometric method (System 3 Scanning Spectrofluorometry, Optical technology devices, inc. Elmstord, New York, 10523) by Barrett&Kirschke. The viability of the sperm was determined after its freezing-thawing. Sperm smears were eosin stained and live:dead-ratio was examined using an Olympus BX41 phase contrast microscope (Olympus Corporation, Japan). The significance of differences in the studied groups was determined using the Mann-Whitney U-test. There were no significant differences in the activity of catepsins B and L in the spermoplasm of stallions with normal and low percentages of viable spermatozoa after freezing-thawing. It was found that in the group of stallions with a normal percentage of viable spermatozoa after freezing-thawing, the activity of cathepsin H in the spermoplasm was significantly higher than in the group with a low percentage of viable spermatozoa (P = 0.0219). Free radicals formed during freezingthawing of sperm can damage cell membranes, leading to loss of sperm viability. Thiol cathepsins are involved in the degradation of oxidatively modified proteins and, apparently, it is cathepsin H that is most actively involved in this process in the sperm of stallions. We assume that the low activity of cathepsin H in the seminal plasma of stallions with a low percentage of viable spermatozoa indicates a high involvement of this enzyme in the protection of sperm membranes from oxidative damage. The research was supported by the Russian Science Foundation grant No. 20-16-00101. [ABSTRACT FROM AUTHOR]

The objective of the study was to assess the level of spontaneous oxidative modification of sperm plasma proteins (OMP) in young and mature stallions as indicators of the severity of oxidative stress. Sperm from 12 stallions aged 14-18 years (average age 15.8±1.9 years) (Group I) and 12 stallions aged 3-5 years (average age 4.3±0.6 years; Group II) was obtained during the breeding season (February-May). Each ejaculate was evaluated by volume, concentration, total number of spermatozoa, as well as by the progressive motility and survival of spermatozoa in diluted sperm during its hypothermic storage at +4°C. For a quantitative assessment of the OMP level, a spectrophotometric analysis of 2,4-dinitrophenylhydrazones formed during the interaction of carbonyl derivatives of proteins with 2,4-dinitrophenylhydrazine was carried out (SF-2000, Russia). The level of aldehyde- and ketonedinitrophenylhydrazones of neutral (ADNPHn, KDNPHn) and basic (ADNPGb, KDNPGb), and the total level of OMP (S OMP) was measured. Significance of differences was assessed by the Mann-Whitney test, the results were statistically significant at P = 0.05. The total level of spontaneous OMP of sperm plasma in aged stallions is statistically significantly higher than in young stallions (531.7 and 384.3 Uod/g protein, respectively, P < 0.05). This indicates a higher degree of oxidative stress in Group I, a more significant damage to the amino acid residues of sperm plasma proteins. In Group I a shift in the absorption spectrum towards neutral aldehyde derivatives (367.6 and 255.8 Uod/g protein, respectively, P < 0.05) was noted. We assume that the pro-oxidant systems in a stallion body increasingly prevail over the protective ones with the age. This leads to an increase in the level of OMP in the sperm and a decrease in the survival of spermatozoa during the hypothermic storage of diluted sperm. Authors acknowledge financial support from Russian Science Foundation, Grant No: 20-16-00101. [ABSTRACT FROM AUTHOR]

It is necessary to consider the factors affecting the dynamics and blood glucose (BG) level to maintain a horse's high performance and health during intensive training. The study aimed to research the influence of the feeding regime on the change in BG level in the Orlov trotter horses during the period of intensive training (summer) in the conditions of the stud farm's training center in the Kaluga region (Russia). Horses aged 2 to 4 years, stallions (n = 7), and mares (n = 5) received commercial mixed feed three times a day and grass hay in free access. Four times a week after lunch, horses are released into the paddock with cut grass. Blood was collected from the jugular vein. Blood was collected before morning feeding and then every hour until four h after morning and afternoon feeding. The dynamics of BG changes depending on the presence or absence of the grass paddock after feeding were evaluated. If horses remained in the stall after feeding, the BG level gradually increased, reaching a maximum (4.95 ± 0.21 mmol/L) 3 hours after feeding and was significantly higher (P = 0.05) than when they were immediately moved to the paddock with grass. The maximum BG concentration in horses in the paddock was observed 1 hour after feeding (4.55 ± 0.21 mmol/L); it didn't have significant differences with the BG level after 1 hour in "stall horses" (4.5 ± 0.14 mmol/L). Then the BG level of the "paddock horses" gradually decreased, and in the "stall horses" increased. No significant difference in BG levels was observed 4 hours after feeding. When horses can walk in a paddock after feeding concentrates and eat grass, blood glucose levels do not rise and tend to decrease. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the dynamics of steroid hormones (pg/ml) in 2-year-old mares and stallions. During preparatory training, at rest, stallions and mares had similar testosterone levels (0,98±0,745-0,82±0,013), estradiol (21.18±5.05-22.50±3.01) and cortisol (90.17±2.11-83.26±2.48), respectively. In response to submaximal power, stallions and mares expend their reserves uneconomically, expressed in an increase of testosterone (9.54±0.353 - 19.59±1.85) and cortisol (203.07±8.70 -245.57±18.60). The estradiol in stallions fell 27% to 16,68±3,01, and in mares increased by 9% (24.50±0,89). At the end of the preparatory period, stallions showed increase in testosterone by 13 (to 13.47±2,21), cortisol 1.5 times (139,12 ±of 12.97), a fall in estradiol levels 5.3 times (to 4.00± 1,72). The content of testosterone in mares increased by 8.6 times (to 7.09±0.97), cortisol by 2.2 times (to 185.24±3.78), and estradiol fell by 6.8 times (to 3.30±0.84). The swing movement at the end of the preparatory period caused a significantly (P = 0.999) less increase in testosterone in stallions (up to 2.63±0.42) and mares (9.39±3.09) in contrast to the previous period. The cortisol content in stallions increased by 88% (to 381.5±17.3), in mares by 384% (to 711.80±47.50). Estradiol concentration decreased 10-fold in stallions (to 1.40±0.576; P = 0.999), and 3.5-fold (to 6.94±0.829; P = 0.999) in mares. Conclusion: the training is sufficient for adaptation of stallions to the racetrack. For mares, the duration of the preparatory training is not sufficient. [ABSTRACT FROM AUTHOR]

The research aim was to study the effect of the elemental status of stallions detected by concentration of chemical elements in the mane hair on the quality indicators of sperm. The research was done on stallions of Arabian breed (n = 54) aged from 5 to 15 years. Hair samples were taken from plot of the mane in the area of projection of the first cervical vertebra (not less 0.24g). The elemental composition of biosubstrates was explored for 5 toxic elements (Al, Cd, Pb, Sn, Sr) by atomic emission and mass spectrometry (AES-ICP and MS-ICP). Spearman rank correlation was calculated at the first stage of the experiment that demonstrated negative correlation of Sr in the hair with volume of ejaculate (r=-0.55; P < 0.05) and total number of progressive motile spermatozoa (r=-0.31; P < 0.05). The entire research sample was divided into three groups: I - concentration of Sr in the hair below 1.88 mcg/g; II - within 1.89 - 3.89 mcg/g; III - above 3.9 mcg/g. Comparative analysis showed that stallions with Sr levels below 1.88 mcg/g (group I) exceed stallions from group II by ejaculate volume by 18.2%; sperm survival in hypothermic sperm preservation after cryopreservation by 24.1% (P < 0.05); total spermatozoa number by 14.6% (P < 0.05); total number of progressive motile spermatozoa by 15.0% (P < 0.05). Difference in the value of the studied parameters between the animals of groups I and III was even more pronounced and was at the level of 38.2% (P < 0.01); 34.7 (P < 0.05); 23.7 (P < 0.05); 26.7% (P < 0.05), respectively. The research was carried out with the support of Russian Science Foundation (project ?. 17-16-01109 P). [ABSTRACT FROM AUTHOR]

The formation and functioning of the animal reproductive system occurs as a result of the coordinated interaction of a wide range of genes. To search for causal mutations, work was carried out to search for polymorphic variants in the marker regions detected using GWAS. The four single-nucleotide substitutions in the exon of the GRM8 gene identified during the studies and the association of these SNPs with sperm quality was carried out. Semen from 22 stallions was collected. Sperm volume, concentration and progressive motility were assessed. Sequencing of the sections of the candidate GRM8 gene was carried out using an Applied Biosystems 3500 genetic analyzer. For the rs1138419111 genotype, no significant differences were found in the studied parameters. According to the identified single nucleotide substitution rs1147388106, the highest ejaculate volume was in stallions with the GG genotype (55.9±26.5 ml) compared to stallions with the GA genotypes (32.5±13.9 ml) and AA (18.0±33,6) (p < 0.05). When analyzing data on SNP rs395286150, stallions with a heterozygous CT genotype had the best sperm quality. Thus, the cell concentration was 317.0±66.5 million/ml in stallions with the CT genotype, 209.6±58.2 and 189.5±74.9 % with the CC and TT genotypes, respectively (P < 0.05). The progressive sperm motility of stallions with the CT genotype was 65.5±20.5% versus 48.7±22.0% in stallions with the TT genotype and 48.4±18.6% with CC. Analysis of data on SNP rs394524550 revealed a significant effect of the genotype on progressive motility. Stallions with the AG genotype had a progressive motility of 64.6±16.3%, and those with GG and AA 32.7±15.7 and 49.6±18.1%, respectively (P < 0.05). Thus, as a result four single nucleotide polymorphisms were identified in the exon of the GRM gene. Three of them were significantly associated with such indicators of sperm quality as ejaculate volume, concentration and progressive motility. Project No. 0445-2021-0011. [ABSTRACT FROM AUTHOR]

Tests the hypothesis that prolactinmediates the increase in seminal volumes induced by sexual stimulation in stallion. Collection of semen from six stallions every other day; Assumption on accessory sex glands; Seminal and behavioral characteristics of ejaculates collected from stallions.

The article discusses research by D. L. Thompson, reported in the current issue, on growth hormone and prolactin concentrations in plasma of horses and sex differences and the effects of acute exercise and administration of growth hormone-releasing hormone. It notes that resting concentrations of prolactin, in contrast, were greatest in intact mares and stallions, indicating that the gonads likely influence the degree of prolactin secretion.

The article reports on study which examined if gastric administration of water, salt, starch or various nitrogen sources would cause riese in the prolactin concentrations in horses. The authors of the above study found that each nutrient administred directly to the stomach increased prolactin amounts in manner similar to that caused by meal ingestion.

The article reports on study which examined quantities of prolactin, growth hormone cortisol, insulin, glucagon, urea and amino acids in plasma of mares and stallions in last hours of their feed deprived periods. The study concluded that no hormone or metabolite differed with respect to time across days when the stallions were not fed.

The article focuses on a research related to the short-term patterns of growth hormone (GH) secretion in mares and stallions; and also examining the effects of exercise, Sexual Stimulation, and Pharmacological Agents on mares and stallions. It mentions that the administration of sulpiride has increased prolactin concentrations in plasma of mares.

The article discusses the variation of semen harvested from animals including bulls, rams and boars. It cites on the inherited conditions associated with testicular defects, abnormal spermatogenesis and abnormal sperm found. The article also discusses the environmental factor for the quality of the semen which may be permanent or temporary.

Presents abstracts of several articles on horse species. "Handling Method Influences Equine Urinary Calcium and Nitrogen," by C. I. O'Connor, B. D. Nielsen and M. Mayack; "Economic Evaluation of Gestation Crates Versus Loose-Housing Systems for Gestating Sows," by M. Ellis, M. E. Kocher and G. D. Schnitkey; "The Effect of MOS Supplementation on Immune Response of Mares and Their Foals," by K. R. Spearman and E. A. Ott; "Influence of Season and Cooling Device During Commercial Shipment of Stallion Semen," by G. W. Webb, M. J. Arns, M. A. Harris and C. L. Dekat.

The objective of this study was to determine the frequency and duration of nursing bouts in foals. This information is essential in order to estimate nutrient intake of foals and nutrient demands on nursing mares. Seven foals out of Hungarian sport half-breed (primarily Thoroughbred breeding) mares (5 to 15 yr of age) and by Holstein, French and Dutch stallions were used in this study that was conducted at the Demonstration Farm of the College of Nyiregyhaza, Napkor, Hungary. Horses were housed in box stalls ranging in size from 10.5 to 15 m2. Horses were fed approximately 8 kg of a mixture of grass and alfalfa hay, and 4 to 6 kg of corn and crimped oats. Mares and foals were observed for a 24-h period on d 10 and 20 after foaling. Length of time spent nursing and the number of times a foal nursed, as defined as any suckling attempt lasting longer then 27 seconds, were recorded. Additionally, the length of time foals spent lying on the ground resting was recorded. Data were analyzed as repeated measures with hour of day within foal and day of lactation being the repeated variable. Nursing bouts per hour decreased from 3.85 ± 0.21 on d 10 to 2.85 ± 0.21 on d 20 (P < 0.02). The average duration of the nursing bouts was 1.22 ± 0.05 min on d 10 and 1.11 ± 0.05 min on d 20 (P = 0.15) resulting in a decrease (P < 0.03) in average time spent nursing per h from 4.67 ± 0.34 min/h on d 10 to 3.18 ± 0.34 min/h on d 20. In contrast, time resting remained unchanged with an average of 28.7 ± 1.1 min/h spent resting on d 10 as compared to 27.8 ± 1.1 min/h on d 20. The greatest number of nursing bouts/h and the longest time nursing within an hour were observed from 0600 to 0659 while the lowest were from 0300 to 0359. The second greatest number of nursing bouts and time nursing within an hour was from 1600 to 1659. The duration of resting periods was reduced when nursing activity was greatest and corresponded to the time when mares were being fed. This study demonstrates there are changes in duration and frequency of nursing bouts of young foals during a 24-h period and across days of lactation that must be considered when estimating milk production and consumption. [ABSTRACT FROM AUTHOR]

Data (N =1,289) were collected from 2001 through 2005 on Korean native horse called Jejuma by the evaluations of Jeju horse commission to estimate genetic parameters for head length, withers height, back height, croup height, body length, chest depth, chest width, hip width, croup width, croup length, chest girth, and cannon circumference as conformation traits of a horse. Estimates of heritability and genetic correlations of these traits were obtained with derivative - free REML. Model included animal genetic and residual random effects. For 12 conformation traits, sex, age, and registration status were used as a fixed effect. For the sex effect, there were few quantifiable differences between mares and stallions. Non - registered horses were much higher and lengthier than those of registered horses. Single-trait analyses were initially done to obtain starting values for multiple-trait analyses. Estimates of heritability for 12 body measures were moderate to high and for the height traits (withers height, back height, and croup height) were moderate (.45 ~.55). The lowest estimate was found for the hip width (.08) while highest values were chest width and body length (.72 ~ .62). Estimates of genetic correlations between cannon bone circumference and head length and withers height and back height were .80 and .98, respectively. [ABSTRACT FROM AUTHOR]