Recipient Organization
COLORADO STATE UNIVERSITY
(N/A)
FORT COLLINS,CO 80523
Performing Department
Clinical Science
Non Technical Summary
Lameness originating from the foot represents the most common source of lameness in horses. Additionally, hoof size, shape and balance have been identified as possible risk factors for severe musculoskeletal injuries in racehorses and have an impact on whole limb soundness as they influence limb motion, as well as the forces placed on the structures within a limb.While equine veterinarians are starting to recognize the role of the internal and external hoof characteristics on lameness, this still remains a component of therapy over-looked. Recently, an association between a long toed, low heel hoof conformation and hindlimb lameness was identified in a large group of performance horses. Additionally, environmental conditions and intensity of exercise have been associated with changes to the external hoof angles in Thoroughbred racehorses. However, the effect of beginning training and age at which training is started on hoof appearance and lameness in American Quarter Horses has not been described.Our goal is to follow a group of young American Quarter Horse performance horses entering training just prior to their 2 or 3-year olds years and to monitor hoof conformation and development of lameness over a six-month period of early training. The goals are to determine how hoof conformation changes as young horses begin training, to determine whether age (2 vs. 3-year olds) at which juvenile American Quarter Horses enter work affects hoof conformation, and if the development of lameness corresponds to changes in hoof shape and size. We will record hoof size and balance, limb conformation, and fore- and hindlimb lameness of all four limbs. We expect that the hooves of horses entering training as 2 year-olds are more likely change compared to 3 year-olds. In addition, the 2 year-olds with the large changes to hoof appearance will be more likely to develop lameness compared to 3 year-olds. A long term goal of this study is to identify if changes to hoof appearance correlates to lameness, and to further determine if changes to hoof appearance precedes lameness.
Animal Health Component
100%
Research Effort Categories
Basic
0%
Applied
100%
Developmental
0%
Goals / Objectives
Theoverall objectiveof this study is to follow a group of young American Quarter Horse performance horses entering training just prior to their 2 or 3-year-old years and evaluate the effect of initiation of training on hoof conformation (size, shape, balance) and lameness incidence by following them over a six-month time period. All measurements will be performed at baseline prior to entering training and every 60 days over six months (four collection time points). The long-term goal of this study is to identify if changes to hoof appearance correlates to lameness, and to further determine if changes to hoof appearance precedes lameness.We propose three specific aims:Specific Aim 1) To observe the effect of initiation of training on hoof conformation (size, shape, balance).Radiographs and photographs will be performed of all four hooves, and hoof size, shape and balance will be determined. Limb conformation, height, and weight will be recorded.Specific Aim 2) To determine the effect of age (2 versus 3-year-olds) at the time of training initiation on hoof conformation.Radiographs and photographs will be performed of all four hooves, and hoof size, shape and balance will be determined. Limb conformation, height, and weight will be recorded. Lameness will be recorded subjectively and objectively (Lameness Locator®).Specific Aim 3) To determine if there is a relationship between changes in hoof conformation and development of lameness.Fore- and hindlimb lameness will be determined both subjectively using AAEP lameness grading scale and objectively using Lameness Locator®. Horses' level and frequency of exercise will be recorded over time.
Project Methods
Power Analysis:Based on preliminary data in a group of 2 and 3 year-old American Quarter Horses entering training, when comparing the change in toe angle over 4-5 months, we expect the 2 year olds having an increase in toe angle of 2.3°and the 3 year old horses to have an increase in toe angle of 0.3°with a common standard deviation of 2°. To obtain power of 80% with alpha 0.05, 17 horses are needed per group. With 20 horses per group, this would provide power of 0.87.Horses:American Quarter Horses (age 2 to 3 years) which have been enrolled in the colt training program in the Equine Sciences department at Colorado State University in Fort Collins, CO. These young horses are bred for western performance or cutting. At the beginning of the study, they will be approximately 1 1⁄2 and 2 1⁄2 years and will be 2 and 3-year-olds at the termination of the study. Approximately 30 to 35 horses enter this colt training program every year and are provided from the same group of ranches. Approximately 55-60% of these horses are coming 2-year-olds and 40-45% coming 3-year-olds per year: 16-21 2-year-olds and 12-16 3- year-olds.Timeline:Two- and three-year-old American Quarter Horses will be recruited from the colt training course that is held every spring and fall at Colorado State University. Horses will arrive in September 2020 and will be evaluated starting in October. They do not begin forced exercise until November, so their baseline measurements will be pre-training. These horses will be evaluated every 60 days until their sale, which occurs at the end of April. Data will be compiled and analyzed by the end of May 2021. A manuscript will be written and submitted by July 2021.Horse management:All horses will be kept in outdoor pens for the first 4 months (October through end of January) with 6-8 horses per pen, and then will be stalled separately for the last 2 months. All horses will have routine farrier work on a 6-week interval and will be barefoot. Weekly training logs will be kept for each horse, recording type and intensity of exercise. Any illness or lameness will be recorded, as well as treatment. If the illness/lameness results in inability for the horse to perform its intended level of exercise, it will be removed from the study.Study Design:We will prospectively enroll thirty American Quarter Horses. From preliminary data, we have already enrolled seven 2-year-olds and three 3-year-olds. We will enroll an additional 13 - 2-year-olds and 17 - 3-year-olds, to reach a total of 20 horses in each group. Horses will be excluded if there is a baseline lameness greater than a grade 1 out of 5, using the AAEP grading scale. Horses will be examined at four 60-day intervals (days 0, 60, 120, and 180), and these evaluations will be 1-2 weeks after they have received routine farrier work. At each time point, all horses will be weighed using a calibrated scale and height at the withers will be measured.Musculoskeletal examination and lameness evaluation:Horses will be subjectively assessed for lameness at the walk and trot over an asphault surface in straight line in hand, and objective lameness evaluation will be performed using an inertial sensor system (lameness locator®). Objective values of head movement (HDMax, HDMin, and vector sum (VS)) and pelvic movement (PDMax, PDMin, and vector sum (HS)) asymmetry will be recorded. Lameness evaluations will be video recorded, and all four limbs will be assigned a subjective lameness score using the AAEP lameness scoring system (0-5 scale) at a later time by three blinded observers.Distal Limb Photographs:Digital photographs at all four time points will be obtained with horses standing squarely on four 3" wooden hoof blocks. Lateral and dorsal photographs will be obtained of all four distal limbs (carpus/tarusus and distally) to assess distal limb conformation (angular, rotational, flexural limb deformities). Lateral, dorsal, and solar digital photographs of all four feet will be performed to assess sagittal and medial-lateral hoof balance, toe and heel angles, toe and heel lengths, lateral and medial wall heights, width at the widest part of the foot, length of foot on the weightbearing surface, and frog base width and length (Figures 1-3). A ruler will be included in each photograph so that measurements can be compared across all time points. All photographs will be uploaded to a computer so that measurements can be done digitally using commercial software (IC Measure, The Imaging Source, LLC).Radiographs:Lateromedial (LM) and dorsopalmar/plantar radiographic projections will be obtained of both fore and hind hooves at all four time points. Horses will stand square with all four hooves on wooden blocks and the primary beam will be centered approximately 1cm above the ground (approximate level of thesolar surface of the distal phalanx). The generator-plate distance will be set at 24". On the lateromedial radiograph, the palmar/plantar angle of the distal phalanx (PADP) will be measured and recorded (Figure 4). On the dorsopalmar/plantar radiographs, medial to lateral balance will be assessed. Measurements will be made using commercial software (IC Measure, The Imaging Source, LLC).Facilities:All horses are housed at the Equine Sciences facility. There are 10 group paddocks and 35 stalls, where horses will be housed. Horses are worked in 2 indoor arenas which receive regular maintenance. A calibrated scale is available to weigh horses. The CSU Equine Field Service has 2 radiograph units (generator and Sound Digital plate) for use in this project. There are two inertial sensor systems (lameness locator) that are available for collection of objective lameness data. In addition, high quality video and digital photography systems are available for use by the CSU veterinary teaching hospital. Computers, with appropriate analysis software, and office space are available for both PIs at their respective universities.Exercise Log:A weekly exercise log will be kept for each horse during the study period. Type of exercise (ground versus ridden work), number of days, amount, as well as intensity level will be recorded.Statistical Analysis:For statistical analysis, STATA (version 13.1)awill be utilized. Data will be assessed visually (histograms), and Shapiro-Wilk tests will be performed todetermine normality for all measured variables. Repeated measures ANOVA will be used to compare each variable (lameness, radiograph measurements, and photographic measurements) across time using all horses. Repeated measures ANOVA will also be used to compare 2 versus 3-year-olds. Logistic regression will be used to assess if a large change in any of the hoof shape or size variables is associated with lameness in a particular limb. Multiple comparisons for each time point will be calculated using the Sidak post-hoc test. Significance for all statistical tests will be set at P<0.05.