RESUMEN

Cyathostominae are ubiquitous to grazing horses and regarded the most prevalent internal parasite in the horse. Unfortunately, decades of indiscriminate use of anthelmintic drugs have resulted in the development of resistance in cyathostomins to all currently available drug groups, the most recent being a documented lack of efficacy to the macrocyclic lactones (ML). In vivo determination of anthelmintic resistance in horses most often utilises the faecal egg count reduction test (FECRT). Further, a shortened egg reappearance period (ERP) can indicate a change in response to the applied treatment and suggest an upcoming reduction of efficacy. Although both true resistance as demonstrated by the FECRT and shorter ERPs after ML treatment have now been shown in cyathostomins worldwide, the efficacy of ML as regards to cyathostomins in Sweden is currently unknown. The aim of the present study was therefore to determine FECRTs and ERPs after ivermectin (IVM) treatment in Swedish horses. Sixteen equestrian establishments with a minimum of six horses excreting at least 150 eggs per gram faeces (EPG) at screening were selected. For each establishment, FECRTs and ERPs were determined by collecting faecal samples prior to and 14 days after IVM treatment (200 µg/kg), and thereafter at weekly intervals for a total of eight weeks. All participants responded to a questionnaire detailing pasture management methods and anthelmintic routines.Questionnaire results showed that the majority of establishments (69%) only treated horses with anthelmintic drugs if indicated by faecal diagnostics and all of the establishments had a mean FECRT exceeding 99.0% and ERPs ranging from six to over eight weeks. The ERP was shown to increase with age as young individuals were shown to excrete cyathostomin eggs earlier after treatment compared with older horses (R = 0.21, p = 0.015). Riding schools, stud farms and those declaring not to use separate summer and winter paddocks had significantly shorter ERPs (p <0.01).In conclusion, retained ERPs and no confirmed resistance to IVM were found in Swedish equine establishments practising selective anthelmintic treatment, and supports the use of selective deworming regimens as a means of reducing the risk of anthelmintic resistance development.

RESUMEN

BACKGROUND: Training of Standardbred race horses aims to improve cardiovascular and metabolic functions but studies on the effects of different training strategies from breaking till racing are lacking. Sixteen horses with the goal to race as 3-year-olds were studied from breaking (1-year-olds) to December as 3-year-olds. Horses were allocated to either a control (C) or reduced (R) training program from 2 years of age. The aim was to evaluate the effect of reducing the distance of high intensity exercise by 30% with respect to velocity at lactate concentration 4 mmol/l (VLa4), blood lactate and cardiovascular response. All training sessions were documented and heart rate (HR) was recorded. A standardized exercise test of 1,600 m was performed 10 times and a VLa4 test was performed five times. RESULTS: C horses initially exercised for a longer time with a HR >180 beats per minute compared to R horses (P < 0.05) but after 6-9 months, time with HR >180 bpm decreased in C and were similar in the two groups (P > 0.05). Over the 2-year period, recovery HR after the 1,600 m-test decreased in both groups but was within 2 months lower in C than in R (P < 0.05). C horses also had lower resting HR as 3-year-olds (P < 0.01) than R horses. In C, post exercise hematocrit was higher than in R (P < 0.05). There was a tendency (P < 0.1) towards a larger aortic diameter in C as 3-year-olds (C: 1.75 ± 0.05, R: 1.70 ± 0.05 cm/100 kg BW). Left ventricle diameter and blood volume (in December as 2-year-olds) did not differ between groups. There were no differences between groups in post exercise blood lactate concentration or in VLa4. Both groups were equally successful in reaching the goal of participation in races. CONCLUSIONS: Horses subjected to a reduced distance of high intensity training from the age of 2 showed an attenuated heart rate response, but were able to maintain the same VLa4 and race participation as horses subjected to longer training distances.

Asunto(s)

RESUMEN

BACKGROUND: It has not yet been shown that ossification of ungular cartilages (OUC) is a pathological condition. Beside heredity, factors such as sex, age, repeated concussion, local trauma, hoof and body size have been suggested as contributing factors for OUC development. By comparing radiographs of front hooves from cold-blooded trotters with different age we wanted to evaluate when development of OUC in cold-blooded trotters occurs and if and when it stabilizes in relation to age and workload. Diagnosis and grading of OUC were based on radiological field examinations of 649 Swedish and Norwegian cold-blooded trotters' front hooves. A hundred and forty-seven of the horses were re-examined 3-13 years (mean age 9, median 8 years) after the first occasion. All radiographs were evaluated blind, using two different grading systems for OUC. Work load, in form of number of races completed, and body size score were collected from official data. Four statistical ordinal regression models were used, compared and evaluated. RESULTS: We identified a breakpoint at 2.8 ± 0.38 years of age when ossification ends and proposed a simpler grading system with more consistent results. There was no significant correlation between body size and grade of OUC. Comparison of different statistical methods for evaluation of ordinal data revealed a piecewise linear regression model as most suitable. CONCLUSIONS: Individuals with OUC developed this condition during the stage of life when their hooves develop in size. Results from this study can assist equine practitioners when examining and for understanding this condition in their clinical work and is also beneficial for the Scandinavian equine industry when devising breeding programs.

Asunto(s)

RESUMEN

BACKGROUND: Ossification of the ungular cartilages (OUC) in the foot of horses has been studied for more than 100 years. There is a high heritability of this condition but its clinical relevance has remained questionable. Nevertheless, modern equine orthopedic literature ranks OUC as one of top 10 causes of lameness in cold-blooded trotters and stallions of these breeds are excluded from breeding if they have more than mild levels of side bones. Cold-blooded trotters have been used for racing for many decades and official sports data have been available since 1923. A decreased performance is often the only obvious clinical sign noticed by trainers and owners motivating them to seek professional help from veterinarians and farriers. By comparing various performance parameters in Swedish-Norwegian cold-blooded trotters without and with different grades of OUC, we aimed to determine the clinical relevance of ossified hoof cartilages in a population of high-performance horses. Front hooves from 649 Swedish-Norwegian cold-blooded trotters were evaluated radiologically regarding OUC. Breeding index and official sports data originating from strict protocols kept by groups of officials in trotting associations was used for comparison of performance of these horses that together had competed in more than 23,000 races between 1973 and 2009. Generalized linear mixed models were used for the statistical analyses. The response variable was modeled using ordinal logistic models with a multinomial distribution and a cumulative logit link function. The horse was used as a random factor. RESULTS: Significant effects of gender on performance were demonstrated, but no correlations were found between different positions nor grades of ossified ungular cartilage and number of starts, running pace, race winnings, number of races completed in a regular gait. CONCLUSIONS: Ossification of the ungular cartilages does not cause decreased performance in cold-blooded trotters and is therefore most likely not a cause of clinical or subclinical lameness in this breed. Results from this study can assist equine professionals in evaluating and interpreting the clinical relevance of radiological findings on ossified hoof cartilage among heavy and high-performing horses.

Asunto(s)

RESUMEN

OBJECTIVE: To determine whether repeated oral administration of glucose and leucine during the period immediately after intense exercise would increase the release of insulin and thereby enhance glycogen synthesis in horses. ANIMALS: 12 Standardbred horses. PROCEDURES: In a crossover study design, after glycogen-depleting exercise, horses received oral boluses of glucose (1 g/kg at 0, 2, and 4 hours) and leucine (0.1 g/kg at 0 and 4 hours) or boluses of water (10 mL/kg at 0, 2, and 4 hours; control treatment). Blood samples for determination of glucose, insulin, and leucine concentrations were collected prior to and during a 6-hour period immediately after exercise. Biopsy specimens of a gluteus muscle were obtained before and immediately after exercise and at 3, 6, and 24 hours after exercise for measurement of glycogen concentration. RESULTS: When glucose and leucine were administered to the horses, plasma insulin concentration was significantly higher during the 6 hours immediately after exercise than it was when water was administered to the horses. Serum glucose concentration during the 4 hours immediately after exercise was significantly higher when glucose and leucine were administered than the serum glucose concentration when water was administered. Muscle glycogen concentrations did not differ between the 2 treatments during the 24 hours after exercise. CONCLUSIONS AND CLINICAL RELEVANCE: Synthesis of muscle glycogen after intense intermittent exercise was not enhanced by oral boluses of glucose and leucine after exercise despite pronounced increases in plasma insulin and serum glucose concentrations.

Asunto(s)