Young Horses Research Articles

A Closed Reduction of Cervical Spine Subluxation in an Arabian Foal with an External Neck Stabilizer

Cervical spine injuries that impact young horses and foals can result in mild to severe neurological signs or even result in sudden death. There are only a few reports on conservative treatment options for this condition in the scientific literature. If the condition is left untreated, it can lead to the development of degenerative joint disease, resulting in chronic neurological symptoms and discomfort. We present the case of a two-day-old Arabian foal that showed signs of ataxia following a neck injury, being the result of cervical spine subluxation. Radiological examination revealed a dislocation between the second and third cervical vertebrae. At admission to the clinic on the seventh day of life, the foal’s clinical examination parameters were within physiological ranges. The head posture at the presentation was consistently low, the foal could not lift its head above the shoulder joint throughout the whole examination, the neck muscles were spastically tensed and clinical signs of ataxia were present. The foal underwent a closed reduction in the subluxation under general anesthesia and a fiberglass semicircular gutter was created to stabilize the neck in the desired position. The ataxia symptoms began to improve around day 12 post manipulation, and the fiberglass stabilizer was removed after 16 days post manipulation, followed by radiographs. The dislocation of C2/C3 was no longer visible on the radiographs, and the foal was able to assume a normal neck posture after the removal of the fixator.

Exploring factors that influence the behavior response to novel object tests in young thoroughbred horses: investigating sex, test site and auction history

IntroductionThe novel object test is one of the three most common fear tests in veterinary science and employed in several different species. Although having been applied in several different studies in horses, it is surprising that there is no standardized test procedure available for these kinds of tests.MethodsThis study investigated the performance of the novel object test on 42 young Thoroughbred horses to determine the effect of sex (mare or stallion), test sites (round pen or paddock) and whether the horses had previously participated in an auction or not on the behavior during the novel object test.ResultsDifferences in horses’ behavior during the novel object test were primarily attributed to the test sites. The animals showed significant (p < 0.05) intra-individual differences in the novel object test in the round pen and in the paddock. Sex did not affect the direct interaction with the novel object. The horses that had not participated in an auction seemed to actively perceive the novel object more quickly, so that the latency to first fixation on the object was significantly shorter.DiscussionIn order to obtain comparable results, it is recommended that novel object tests should be performed at the same location and under identical conditions. Furthermore, it is important to consider the individual behavior of each horse.

First report of ivermectin resistance in natural infected Foals by Parascaris spp. in Tiaret, Algeria

Equine parascarosis is a Worldwide endoparasitosis, caused by Parascaris spp., affecting mainly younger horses. This disease is considered as the most pathogenic parasitosis of young horses. In Algeria, no knowledge of the resistance of Parascaris spp. to Ivermectin is published. For this reason, the present study aims to evaluate the frequency of Parascaris spp. and the anthelmintic efficacy of Ivermectin and Fenbendazole against this parasite in a foal population in Tiaret, Algeria. Ninety–one foals were examined for the presence of Parascaris spp. from two stud farms. Among the positive, thirty–two faols were treated with Ivermectin formulations (Ivoral® and Eqvalan®) and Fenbendazole (Funcur®) at their recommended dosages. Fecal egg count reduction testing (FECRT) was used to determine the efficacy of each anthelmintic. Parascaris spp. was detected in 61 foals (67.03%). Decreased efficacy (reduction of Parascaris spp. fecal egg counts by less than 90%) was found for the two Ivermectin formulations (46.45% for Ivoral® and 70.29% for Eqvalan®). Nevertheless, fenbendazole showed 100% efficacy in all foals sampled in this study. These first data indicate that Ivermectin–resistant Parascaris spp. populations are present on horse farms in Algeria. Findings from this study can be used to create a more sustainable approach for parasite control programs.

Behavioural and physiological indicators of hoof trimming stress in restrained juvenile stable- and forest-born Konik Polski horses: a cross-sectional and longitudinal field study

Behavioural and physiological responses are suggested indicators of horse stress. The responses can vary according to changing intrinsic factors, for example, age or habituation to human handling and restraint.In this study, the same 53 Konik Polski horses that were born in either a forest-born (FB) sanctuary or a stable-born (SB) sanctuary were assessed for consistency in their behavioural and physiological responses over months, and the relationship between avoidance behaviour (withdrawals, head shakings, jerks, rearings, stepping and their total: AB), leaning behaviour and cardiac responses (heart rate: HR and heart rate variability HRV: SDRR and RMSSD during routine hoof trimming at 6, 12 and 18 months of age was examined. Additionally, the effect of age and birthplace on avoidance behaviour and cardiac parameters and their correlations was investigated.The avoidance behaviour, leaning behaviour and HR and HRV parameters differed between SB and FB horses (P < 0.01). A significant effect of increasing age/habituation was found in each birth-place group at each age (both effects P < 0.01). Additionally, the correlations of and between behaviour and cardiac parameters were fairly consistent both over age and within groups. The findings indicate that physiological and behavioural markers that are frequently used may not adequately represent the stress status of restrained horses; rather, they may only represent the animals' short-term, current state. Age and prior experience are significant factors to consider when evaluating stress related to husbandry management procedures. Providing that the differences between forest and stable horses remain until 18 months old, the rearing conditions up to weaning would seem sufficient to develop a specific human reception in young horses.

Respiratory viruses affecting health and performance in equine athletes.

Some respiratory viruses can affect equine athletes, with acute respiratory clinical signs leading to a reduced ability to perform. The direct association between equine respiratory viruses and athletic performance is unclear in subclinically affected horses. This narrative review summarises the current evidence on respiratory viruses most commonly detected in performing horses, including equine herpesviruses, equine influenza virus, equine rhinitis viruses, equine arteritis virus, and equine adenovirus 1. It covers their virology, clinical manifestations, epidemiology, pathogenesis, diagnosis, and control measures, with a focus on their impact on performance. Molecular diagnostics on nasopharyngeal swabs are the preferred method for detecting equine respiratory viruses nowadays. Studies highlighted in this review reveal a high prevalence of equine herpesviruses -particularly gammaherpesviruses- in the airways of both healthy and diseased horses. In contrast, equine rhinitis A virus, equine arteritis virus, and equine adenovirus 1 are the least common viruses. Transportation contributes to spreading equine infectious diseases across countries and can temporarily weaken the immune system, increasing the risk of respiratory viral infections and reactivation of latent equine herpesviruses. Moreover, respiratory viral infections are frequently observed in young horses starting their training. Although there is limited evidence on the specific impact of equine respiratory viruses on performance, this review emphasises that vaccination and care management are essential strategies for limiting the spread and severity of outbreaks in sport horses.

Larval cyathostominosis in horses

Small strongyles are the most common parasites of horses, capable of surviving different climate conditions. Though the infection is usually asymptomatic, young horses are considered more prone to developing a parasitic syndrome called larval cyathostominosis. In most cases, gastrointestinal symptoms are most prevalent. Treatment is based on the use of fenbendazole and moxidectin. Diagnosis is difficult and serological methods are still under development. The main prevention methods include regular coprological testing, pasture rotation, co-grazing with ruminants, and regular removal of faeces from the pasture.

Comparison of blood parameters in two genetically different groups of horses for functional longevity in show jumping.

In order to find early selection criteria to improve the longevity of show jumping horses, a specific protocol was designed. Before entering competition, young horses selected from extreme stallions for longevity were measured for many traits, including blood parameters. Blood samples were taken from 952 horses aged 2-4years old, sired by two groups of stallions: one with unfavorable (U) and the other with favorable (F) extreme estimated breeding values for functional longevity. These breeding values were previously calculated from data on 202,320 horses that participated in show jumping competitions between 1985 and 2022. Functional longevity was defined as time spent in competition, adjusted for the level of performance. The 59 measured parameters included hematology, proteins, cytokines, liver and kidney function, bone and joint health, oxidative stress and endocrinology. Heritability was estimated using a mixed model that accounted for the effect of age, sex, estimated weight, visit (place and date of collection), and animal random additive value with 10,280 horses in pedigree. A Partial Least Square logistic regression was performed to predict the sire group. Age, sex and estimated weight significantly affected 36, 19 and 16 variables, respectively. The visit had a significant effect on all variables. Heritability estimates were high, with 75% higher than 0.20% and 30% higher than 0.50. The most heritable traits included mean corpuscular volume (0.92, se 0.11), mean corpuscular hemoglobin (0.90, se 0.11), white blood cells (0.55, se 0.13), total alkaline phosphatase (0.68, se 0.12) and percentage of γ-globulin (0.57, se 0.12). The logistic regression that predicted the group of sires favorable for longevity identified 16 significant variables. Key findings included: lower mean corpuscular hemoglobin (p-value < 0.001), lower mean corpuscular volume (p-value < 0.001), lower number of white blood cells (p-value < 0.01), higher percentage of intestinal and bone alkaline phosphatase (p-value < 0.01) for a lower total alkaline phosphatase (p-value < 0.01), higher percentage of α2-globulin (p-value < 0.001) and lower percentage of β1-globulin (p-value < 0.01). Blood parameters measured at rest in young horses may be predictive of their genetic value for functional longevity in show jumping.

Distal sagittal forelimb conformation in young Walloon horses: Radiographic assessment and its relationship with osteochondral fragments.

Osteochondral fragments within equine joints are commonly encountered and may predispose to lameness and limitation to sport purposes. Factors leading to this condition include genetic, nutritional and environmental conditions. However, few studies have evaluated the impact of conformation traits and their correlation with osteochondrosis. This study, based on the radiographic screenings of young horses born in Wallonia (266 individuals, 532 forelimbs), evaluated the correlation between foot, fetlock conformations of the front limb, height at the withers and presence of osteochondral fragments. Moreover, for all traits significantly associated with the presence of osteochondral fragments, a Receiver Operator Characteristic (ROC) curve, area under the curve and optimal cut-off value were calculated to predict the occurrence of fragments. Mean dorsal hoof wall angle was 52.36°, dorsal and palmar angle of the third phalanx were respectively 49.83° and 2.99°, and dorsal metacarpophalangeal angle 147.99°. Moreover, the prevalence of upright feet, defined as having an inclined profile of >2° steeper in relation to its contralateral counterpart, was 24%. Increased palmar angle of the distal phalanx was significantly correlated (P < 0.05) with presence of fragments located at the dorso-proximal margin of the proximal phalanx. The associated area under the curve was 0.623 (95% CI: 0528-0.717, P < 0.05) and the optimal cut-off value to predict fragment occurrence was 2.95° (sensitivity 77.3%; specificity 52.9%). Furthermore, the third metacarpal bone diameter of the left forelimb and height at the withers were significantly (P < 0.05) correlated with the presence of osteochondral fragments in general and within tarsocrural and metatarsophalangeal joints specifically. The area under the curve was 0.585 (95% CI: 0.513-0.656, P < 0.05) with an optimal cut-off value of 152.5 cm (sensitivity 85.1%; specificity 31.2%) for height at the withers to predict presence of osteochondral fragment; to predict the occurrence of osteochondral fragment in any joint on the basis of the third metacarpal bone diameter, the area under the curve was 0.595 (95% CI: 0.524-0.667, P <0.05) and the optimal cut-off value 34.9 mm (sensitivity 52.5%; specificity 64.9%). This study provides information about phenotypic traits associated with osteochondral fragments in horses. Although the diagnostic accuracy of these traits to detect osteochondral fragment was limited, the identification of more phenotypic characteristics could, in the future, make it possible to generate models for accurately identifying individuals at high risk of osteochondral fragments on the basis of their phenotype.

Ultrasonographic assessment of equine metacarpal cartilage thickness is more accurate than computed tomographic arthrography.

Articular cartilage can be directly imaged using ultrasonography. The fetlock is a common site of osteochondrosis, with the sagittal ridge of the third metacarpal bone most commonly affected. In osteochondrosis, cartilage thickening may be an initial finding. This postmortem study investigated the ability of ultrasonography to accurately measure the dorsodistal articular cartilage of the third metacarpal bone in young horses, compared to computed tomographic arthrography (CTA) and histological measurements. A total of 33 metacarpophalangeal joints from 18 horses between the ages of 12 days and 10 months old were imaged ultrasonographically and with CTA and sectioned and measured using histology. Imaging measurements were made by two observers. Despite overall weak agreement between ultrasonography and histology, the best agreement was at the distal aspect of the sagittal ridge of the third metacarpal bone. Interobserver agreement at this site was also moderate. CTA showed poor agreement overall with histology. Cartilage thickness decreased with age on ultrasonography, CTA, and histology. In conclusion, ultrasonography is a more accurate imaging modality than CTA in the assessment of cartilage in young horses.

Analysis of the jumping performance of young warmblood horses based on the results of breeding competitions in the Czech Republic

The aim of the study was to evaluate the performance of warmblood horses in the Czech Republic based on the results of the Criteria of Young Horses (CYH) breeding competitions. In this study, we focused on the evaluation of horses in jumping competitions for mares, stallions and geldings aged 4 to 6 years. The statistical evaluation is based on the official CYH methodology, which takes into account the different difficulty of competitions for horses of different ages. Data from 2017 to 2021 were used for the evaluation. During this period, 645 horses participated in the competitions with 2691 starts. The statistical analysis evaluated the influence of age, sex, country of origin and breed group on the performance of the horses. Analysis of variance was used for comparison and Scheffe's test was used for subsequent post hoc analysis. Six-year-old horses were rated the highest (22.95 points) despite receiving the highest penalty points (3.29 penalty points). In the sex analysis, the overall rating for stallions was highly significant (P ≤ 0.01) higher than that of geldings and mares. Stallions were the least represented in terms of numbers (22.33%), but they had the highest number of starts per horse (4.75 starts) and the best mean score (23.32 points). A total of 76.12% of the horses that participated in the CYH were of Czech breeding, but their scores were statistically highly significant lower (P ≤ 0.01) than those of imported horses, with a difference in mean scores of 0.91 points. In terms of breed, the most numerous breeds were the Czech Warmblood (43.26%) and then the Czech Sport Horse (17.52%), but these breeds were below average in the overall evaluation (CZEWB 22.53 points, CSH 22.48 points). The third most represented breed was the Holstein horse, which, on the contrary, achieved the best average results (22.83 points) and the performance of representatives of this breed differed highly significantly (P ≤ 0.01) from most other breeds.

Mineralization of equine proximal sesamoid bones precedes articular cartilage and fibrocartilaginous enthesis maturation in early postgestational development.

To describe the development and maturation of equine proximal sesamoid bones (PSBs) in fetuses and young horses using radiography, microcomputed (micro)-CT, and histology. A descriptive study. Forelimb PSBs from 12 equids ranging in age from 105 days of gestation to 540 days postgestation were evaluated. Radiography was used for preliminary assessment of metacarpophalangeal joint and PSB mineralization, and micro-CT imaging was performed to assess mineralized PSBs. Tissue volume, bone volume fraction, height, width, depth, trabecular thickness, and anisotropy were quantified from midplanar micro-CT sections in 3 dimensions. Midsagittal PSB histologic sections stained with H&E and Safranin O/Fast Green were used to determine the ratio of ossification center to cartilage template size and to describe the formation and development of the cartilage template, ossification center, spherical growth plate, articular cartilage, and entheses. Mineralization of equine PSBs is associated with cartilage canals and a spherical growth plate that undergoes endochondral ossification during the late gestation to early postgestational period. The apical, flexor, basilar, and articular ossification fronts demonstrate morphologic variability. Structural organization of the articular cartilage and entheses occurs concurrently with the development of an underlying plate of compact bone. At 540 days postgestation, the fibrocartilaginous entheses of the flexor cortex of the PSB had yet to mature. Equine PSBs mineralize predominantly by endochondral ossification during the late gestation to early postgestational period. Mineralization precedes maturation of the articular cartilage and fibrocartilaginous entheses. The postgestational maturation of the PSB and its surrounding tissues may predispose young horses to developing lesions at these sites, such as apical avulsion fractures, warranting further investigation.

Macroscopic and histopathological description of gastric lesions in horse, donkey, and mule fetuses in the last trimester of gestation.

Limited information is available on gastric diseases in neonatal foals as compared with extensive studies in young, adult, and geriatric horses. Reports on fetuses are scarce. Assess at necropsy stomachs of horse, donkey and mule fetuses in the third trimester of gestation to characterize lesions present during intrauterine life. Forty-six fetal stomachs from both sexes (21 horses, 21 donkeys, and 4 mules) in the third trimester of gestation were collected from a processing plant immediately after slaughter. Measurements of longitudinal and transverse axes, weight and volume and gastric fluid pH were taken, and glandular and squamous mucosae were inspected. All findings of the gastric mucosa and measurements of the stomachs were presented descriptively. Groups were compared statistically, with significance level set at P < .05 for all evaluations. All gastric contents had pH >5.8, and mules had larger stomachs and higher weights compared with horses (P < .05). Macroscopic lesions were classified as hyperemic, punctate, and erosive. Histopathologically, lesions were consistent with a chronic inflammatory process. Our study provides evidence of macroscopic and histopathological lesions in the gastric mucosae of equid fetuses in the last trimester of gestation. Relevant information for perinatology and neonatology is provided regarding the prevalence and classification of preulcerous lesions in equids before birth.

PSII-15 Comparative analysis of equine diets on growth metrics and economic feasibility

Abstract The objective of the study was to assess the impact of two commonly available low non-structural carbohydrate equine diets on growth parameters and economic factors in young growing horses. To do this, young stock type horses n = 11; 6 fillies, 5 colts; body weight (BW) = 380.3 ± 15 kg] were separated into two groups that were balanced by age, sex, and BW. All horses were backgrounded for 14 d on a hay-only diet prior to the beginning of the study. Additionally, each group was assigned to one of two dietary treatments fed at 0.75% BW/d (as fed) twice daily in 12 h intervals for 56 d. Dietary treatments consisted of a leading national brand feed (n = 5) and Thomas Moore Calm and Safe (n = 6). Horses were allowed ad libitum access to Coastal bermudagrass (Cynodon dactylon) hay and fresh water. For the 56-d period, horses were exercised at a light workload for 30 min/d and 4 d/wk. For all growth measurements, a baseline measurement was recorded per horse. Growth measurements were then recorded at 7 d intervals. Data from these growth measurements were analyzed using PROC MIXED in SAS v9.4 with the fixed effects of day and diet. Growth metrics increased on all horses throughout the length of the trial regardless of dietary treatment (P ≤ 0.01), which is expected from young growing horses. A Diet x Day trend towards significance (P = 0.075) was observed for BW, as the leading national brand feed dietary treatment group tended to have heavier BW than the Thomas Moore Calm and Safe during the duration of the study. Additionally, body fat percentage was greater (P = 0.04) in the national leading brand feed group compared with the Thomas Moore group. None of the remaining growth metrics had any statistical difference across diets. Furthermore, there was no difference in dietary intake between dietary groups (P &amp;gt; 0.5). These results suggest that the Thomas Moore Calm and Safe concentrate serves as a good alternative and economically friendly for young growing horses when compared with more traditional feeds currently on the market.

PSI-18 Intra-articular triamcinolone acetonide administration does not affect microbial culture or synovial fluid volume in young, exercising Quarter Horses

Abstract Intra-articular corticosteroids (IAC) are administered to horses experiencing joint inflammation, at times with a concurrent articular antibiotic for prophylaxis. However, information regarding the biologic effects of IAC and potential for microbial contamination in IAC-administered joints is limited in young, exercising horses. The objective of this study was to evaluate the impact of IAC on traditional microbial culture, synovial fluid (SF) volume, and the presence of IAC; hypothesizing negative microbial culture, no change of SF volume, and detection of IAC in SF post-administration. To test this, 2-yr-old Quarter Horses {n = 24; body weight (BW) = 409 ± 6 kg; 825 ± 21 d of age; 12 fillies, 12 geldings) were stratified by BW, age, and sex, and randomly assigned to 1 of 3 treatment groups for a 56-d trial. Horses were housed individually in stalls with runs and fed concentrate offered at 0.75% BW/d split evenly every 12 h with ad libitum Coastal bermudagrass hay and water. Every 21 d, BW and body condition score (BCS) were recorded, and concentrate was adjusted accordingly. Horses were exercised 5 d/wk, up to 45 min/d in a progressive workload using a free-stall exerciser. Blood was collected post-exercise during wk 1, 4, and 7 via jugular venipuncture and lactate (BL) was measured to monitor increasing workload. Intra-articular treatments consisted of 0 mg (CON; n = 8), 6 mg (CORT6; n = 8), or 12 mg (CORT12; n = 8) of triamcinolone acetonide (TA). On d 0, treatments were administered in one randomly selected radiocarpal joint per horse. Following aseptic preparation, SF from both radiocarpal joints was collected before administration (pre), and on d 7, 14, 28, and 56. Volume of SF was recorded, and standard microbial culture and detection of TA were performed by a commercial laboratory. Data were analyzed using PROC MIXED (BW, BCS, BL, SF volume) and PROC GLM (TA) of SAS. For SF volume, data from the contralateral radiocarpal joint were used as a covariate. Horses increased BW and BCS over time (P ≤ 0.01) across treatments. Post-exercise BL increased from wk 1 to 4 and remained increased through wk 7 (P &amp;lt; 0.01). Microbial culture for all horses and time points were negative. Concentration of TA was not evaluated on d 7 due to limited SF volume, but TA was detected on d 14 and concentration did not differ between CORT6 and CORT12 (P = 0.13). Recorded SF volume did not change from d 0 (pre) to 7 but increased to d 56, regardless of treatment (P &amp;lt; 0.01). These results indicate that, based on standard culture, TA administration did not result in positive microbial culture, or decrease SF volume in young horses undergoing regular exercise, however, TA was detectable to d 14.

Anatomy of the Right and Left Ventricular Subvalvular Apparatus of the Horse (Equus caballus).

Due to the growing interest among veterinarians and the increasing market demands, the development of equine cardiology is necessary. Currently, veterinary medicine for companion animals needs to catch up to human medicine-equine medicine included. A common condition in older horses is aortic valve regurgitation resulting from fibrosis, while its more severe form occurs in younger horses or develops due to a bacterial infection. Mitral valve regurgitation, especially dangerous due to the possibility of sudden death, has a better prognosis if the horse has valve prolapse. Tricuspid valve regurgitation usually does not pose a clinical problem, although its severe cases may lead to heart failure. Some pathologies can be treated surgically, which requires excellent knowledge of anatomy. The object of this study consisted of twenty domestic horse hearts. The focus was on the normal and comparative anatomy of the left and right subvalvular apparatus. The number of muscular bellies of the papillary muscles and the type of connection of the muscles were analysed. Moreover, the height of muscle originating from the ventricle wall was determined, the morphological regularity of the papillary muscle was assessed, and the chordae tendineae originating from the papillary muscles were examined. The conducted research allowed for comparing domestic horses with different species through other studies, the authors of which described this particular aspect. Interspecies similarities which may be correlated with the evolutionary relatedness, as well as differences that could reflect adaptation to different lifestyles, environmental conditions, or metabolic requirements of the animals, have been found. This study expands the knowledge of animals' normal and comparative anatomy, and contributes to the development of veterinary surgery, internal medicine, and biology.

PSIII-11 Long-term effects of intra-articular lipopolysaccharide on markers of inflammation and cartilage metabolism in young Quarter Horses

PSIII-11 Long-term effects of intra-articular lipopolysaccharide on markers of inflammation and cartilage metabolism in young Quarter Horses

The effect of the fat to starch ratio in young horses' diet on plasma metabolites, muscle endurance and fear responses.

High-starch diets may affect equine hindgut microbiota and increase blood glucose levels, which may cause unwanted physiological changes, but may also elicit behavioural changes such as increased fear reactions. The purpose of the current study was to feed a high starch (300) and low fat (43; HS_LF) or a low starch (60) and high fat (85; LS_HF, g/kg of DM) concentrate within the available commercial range and investigate how muscle endurance and fear reactions of horses respond to different diets. Twenty Danish Warmblood stallions (4 years) were randomly allocated to two treatments: LS_HF (n = 10) and HS_LF (n = 10) for 9 weeks. During the two last weeks, a single step exercise test was performed, and plasma metabolites and blood gases were measured before and after exercise in a 2 × 2 factorial design. The effect of two diets on fearfulness was tested by exposing the horses to novel objects test (T1 and T2). Plasma metabolites was not affected by diets. However, plasma level of glucose post-exercise (4.9) was lower than pre-exercise (5.6 mmol/L; p < 0.001). Similarly, plasma level of insulin post-exercise (4.2) was lower than pre-exercise (13.1 pmol/L; p < 0.001). Plasma level of lactate dehydrogenase (p < 0.001), non-esterified fatty acids (p = 0.002), β-hydroxybutyrate (p = 0.001), and fructosamine (p = 0.01) post-exercise was higher than pre-exercise. Regardless of type of diets, RRR-α-tocopherol was the dominance α-tocopherol stereoisomers in plasma. In conclusion, during aerobic exercise, fat to starch ratio in horse diets within the normal range had no significant effect on plasma metabolites. However, horses fed LS_HF tended to show more investigative behaviour than horses fed HS_LF.

Međusobni utjecaj reproduktivnog statusa, dobi i osobnosti konja na ostvarivanje punog atletskog potencijala u natjecanjima u preponskom jahanju

The study analysed the results of showjumping competitions of 41 warmblood horses of varying reproductive status, age and personality. In total, 8 stallions, 18 mares, and 15 geldings were included. Horses were divided in the following age groups: young horses 4-7 years old (n=15), mature horses 8-13 years old (n=13) and older horses 14-20 years old (n=13). Horses were also divided according to dominant personality component, obtained by questionnaires: excitability (n=4), protection (n=7), sociability (n=15), curiosity (n=9), horses without a dominant personality component (n=6). Horses in this study were compared to the results of showjumping competitions of the Croatian Equestrian Federation in the past two consecutive years, considering data from 80 classes, 44 tournaments and 3280 starts. The Winter Cup (1.10-1.3) was considered the time of absence of cyclicity in mares while the Summer Cup (1.3-1.10) was considered the full season of reproductive cyclicity of mares. The aim of the study was to determine correlations between the dominant personality component, reproductive status and age of the horse in obtaining optimal results in showjumping competitions. Based on the results, the dominant personality component positively influences the horse’s success in showjumping(ranking, penalties). Excitable horses had the poorest results, especially during the reproductive season (P&amp;lt;0.05). Protective horses had the best results regardless of season. It is likely that determination of the dominantpersonality component could help in better selection of showjumping horses. Geldings had the least seasonal variations, while mares had significantly better results out of season (P&amp;lt;0.05). Stallions also had better results out of season, though the difference was not statistically significant. Recommendations include introducing methods of cycle blockage in mares to improve focus and results in all categories. Contrary to expectations, older horses (14-20 years old) obtained better results than mature horses (8-13 years old). Further research of all observed parameters on a significantly higher sample of showjumpers is required to determine whether the findings here could be applied to the complete population of warmblood horses used in showjumping competitions in Croatia and abroad.

Parasympathetic tone activity, heart rate, and grimace scale in conscious horses of 3 breeds before, during, and after nociceptive mechanical stimulation.

Parasympathetic tone activity (PTA) in response to nociceptive stimulus in conscious non-sedated horses is unknown. Study PTA, heart rate (HR), and horse grimace scale (HGS) at rest and during mechanical nociceptive stimulation. Ninety healthy young adult horses (females, males): 30 each of Friesians, Quarter Horses, and Warmbloods. Prospective control study. The study consisted of habituation to equipment (Day 1), baseline recordings (Days 2 and 3), and nociceptive testing applying mild pressure to the metacarpus (Day 4). Parasympathetic tone, HR, and HGS were recorded simultaneously on Days 2 to 4. Each study lasted 30 minutes and was done in triplicate at 3 different time points per day. Baseline PTA was not different among breeds. It decreased in Warmbloods and Quarter Horses during placement of the stimulus device without stimulation (P < .01). A significant decrease in PTA (P < .001) occurred during nociceptive stimulus (marked in Quarter Horses, intermediate in Warmbloods, and mild in Friesians). Heart rate and HGS increased significantly (P < .001) during the stimulus in all breeds but returned to baseline poststimulation. Friesians required higher pressure (P < .05) to elicit an aversive response to the stimulus. Horses' PTA, HR, and HGS change in response to a mild mechanical nociceptive stimulus with Friesians showing less variation. Stress induced a decrease in PTA in Quarter Horses and Warmbloods but not in Friesians. Friesians appeared to be more tolerant to pain based on PTA, HR, and HGS findings compared with other breeds.

Paramedullary plasma cell myeloma originating from the first cervical vertebra (C1) in an 8‐month‐old Warmblood with tetraparesis: Clinical and pathological findings

SummaryTo the authors' knowledge there is only one report in the literature describing plasma cell paramedullary myeloma in horses as so‐called ‘break out lesions’, originating from vertebral bone marrow and invading the epidural space. This report describes clinical and pathomorphological findings of such. An 8‐month‐old Warmblood colt exhibited acute tetraparesis and a cervical column spinal cord lesion was suspected. Computed tomography revealed C1 osteolytic lesions by a heterogeneous mass. By pathomorphological examination including transmission electron microscopy, a plasma cell myeloma was identified, locally compressing the spinal cord. In tetraparetic young horses traumatic spinal cord injuries, cervical vertebral malformations, and central nervous system infectious diseases represent common differentials. However, osteolytic tumours such as paramedullary (plasma cell) myelomas, as space occupying lesion due to vertebral canal intrusion, should be considered as a cause for severe neurological deficits.