Influence of osteochondrosis on the longevity and racing performance of standardbred trotters and pacers.

OBJECTIVE: To determine the influence of clinical osteochondrosis (OC) on the short-term (2, 3, and 4-year-old) and long-term racing performance and longevity of standardbred racehorses. STUDY DESIGN: Retrospective case-control study. SAMPLE POPULATION: Standardbred racehorses from a single breeding farm born between 2009 and 2017 that survived to racing age (n = 2711). Three hundred eighty-two (14%) horses were OC-affected (829 lesions confirmed arthroscopically during surgical treatment), and 2329 (86%) horses were nonaffected. METHODS: Racing performance data were obtained from an online database and evaluated with multiple linear regression models. RESULTS: Trotters were more likely than pacers to be affected by OC (odds ratio [OR] = 1.4, 95% CI = 1.1-1.9, P = .006). Compared with nonaffected horses, long-term OC-affected horses had 8.8 fewer starts (95% CI = -14.4 to -3.2, P = .002), 1.0 fewer wins (95% CI = -1.9 to -0.1, P = .030), and 3.8 fewer total number of first through third place finishes (95% CI = -6.2 to -1.4, P < .0001). Nonaffected horses had longer careers compared with OC-affected horses, racing 0.32 years longer (95% CI = -0.52 to -0.12, P = .002). Osteochondrosis had no impact on short-term racing performance. Horses with lesions at the distal intermediate ridge of the tibia or lateral trochlear ridge of the talus had decreased performance compared with horses without these lesions. CONCLUSION: Pacers were less likely than trotters to be affected by OC. Affected horses had fewer starts and shorter careers, despite early surgical intervention. CLINICAL SIGNIFICANCE: Osteochondrosis decreases long-term racing performance in racing standardbreds.

Apparent Digestibility of Nutrients, Blood Parameters and Body Development of Dewormed and Not Dewormed Weanlings.

Weanlings undergo rapid body development in the first year of life and, in this period, are more susceptible to helminth infection that can impair their growth. The objective of this study was to compare the apparent digestibility of nutrients, blood parameters, and body development of deworming and not deworming weanlings. Fourteen Mangalarga Marchador weanling colts, on a farm in Northern Minas Gerais, Brazil, were divided into two groups: dewormed (D) and not dewormed (ND) groups. The weanlings were kept separately for 3 months in two pastures of Cynodon nlemfuensis cv. African Star Grass. They also were supplemented with Cynodon dactylon cv. Tifton 85 predried hay ad libitum and 1.5 kg.100 kg-1 of body weight (BW) of corn-based concentrate. Eggs per gram of feces (EPG) of the weanlings were measured monthly. Group D was dewormed (200 mcg.kg-1 BW ivermectin + 2.5 mg.kg-1 BW praziquantel) whenever EPG was ≥500. Group ND weanlings were not treated. The weanlings were subjected to an apparent digestibility assay (total fecal collection procedure). Every month, the weanlings were weighed, evaluated for body condition score, and had withers height, croup height, body length, and thoracic circumference measured. Group ND was infected mainly by small strongyles. There was no difference between groups (P > .05) for morphometric measurements, dry matter intake, and digestibility coefficients, except for apparent digestibility of calcium, which was higher (P < .05) in group D. Small strongyles infection in six- to nine-month-old weanlings fed high grain, nutrient-balanced rations apparently did not affect growth, blood parameters, and apparent digestibility of nutrients.

Effect of Supplementation of Sorghum Silage in Weanling Fillies During the Dry Period in Brazil.

Young horses reach nearly 90% of their final height in the first year of life. However, to achieve their genetic potential, it is necessary to receive adequate nutrition during this period of rapid growth. The objective of this study was to evaluate the effect of supplementation of sorghum silage during a period of limited pasture forage availability, on the body development, and health of Mangalarga Marchador (MM) weanling fillies. Fourteen healthy MM 6-month-old fillies were randomly assigned to one of two groups: GS (consuming silage) and GH (consuming grass hay (Cynodon spp) in addition to 1.5% of body weight (BW) in dry matter (DM) of a fortified corn-based concentrate (17% CP [crude protein]), which was fed in individual stalls divided into two feedings/day for both groups. After concentrate feedings, the experimental groups remained loose in drylot pens of 50 m2, where the assigned forages were fed ad libitum with free access to salt and water. Group feed intake of the forages was recorded. It was assumed they were consuming a forage:concentrate ratio of 50:50. To assess development, the animals were weighed and measured for height at the withers and croup, body length, girth, and cannon bone circumference. The physical condition of animals, including BW, rectal temperature, mucous membrane color, and body condition score were assessed as well as serum biochemical analyses of creatinine, urea, total protein, gamma glutaminotransferase, aspartate aminotransferase, alkaline phosphatase, glucose, magnesium, calcium, and phosphorus concentrations were evaluated. The weights, morphometric measurements, clinical evaluation, and blood collections were done on the first day and every 21 days during the 84 days trial period. The growth performance and serum were subjected to analysis of variance for repeated measures, factoring treatment, and collection period. Despite higher (P < .05) DM and CP intakes by the GH fillies than those GS, there were no treatment effects (P > .05) on any of the development or health parameters measured. The use of sorghum silage as forage source for 84 days during the dry season had no negative impact on the body development and health of MM fillies (6-9 months of age) that were also fed 1.5% BW of a commercial concentrate balanced for growth.

Identification and validation of risk loci for osteochondrosis in standardbreds.

BACKGROUND: Osteochondrosis (OC), simply defined as a failure of endochondral ossification, is a complex disease with both genetic and environmental risk factors that is commonly diagnosed in young horses, as well as other domestic species. Although up to 50 % of the risk for developing OC is reportedly inherited, specific genes and alleles underlying risk are thus far completely unknown. Regions of the genome identified as associated with OC vary across studies in different populations of horses. In this study, we used a cohort of Standardbred horses from the U.S. (n = 182) specifically selected for a shared early environment (to reduce confounding factors) to identify regions of the genome associated with tarsal OC. Subsequently, putative risk variants within these regions were evaluated in both the discovery population and an independently sampled validation population of Norwegian Standardbreds (n = 139) with tarsal OC. RESULTS: After genome-wide association analysis of imputed data with information from >200,000 single nucleotide polymorphisms, two regions on equine chromosome 14 were associated with OC in the discovery cohort. Variant discovery in these and 30 additional regions of interest (including 11 from other published studies) was performed via whole-genome sequencing. 240 putative risk variants from 10 chromosomes were subsequently genotyped in both the discovery and validation cohorts. After correction for population structure, gait (trot or pace) and sex, the variants most highly associated with OC status in both populations were located within the chromosome 14 regions of association. CONCLUSIONS: The association of putative risk alleles from within the same regions with disease status in two independent populations of Standardbreds suggest that these are true risk loci in this breed, although population-specific risk factors may still exist. Evaluation of these loci in other populations will help determine if they are specific to the Standardbred breed, or to tarsal OC or are universal risk loci for OC. Further work is needed to identify the specific variants underlying OC risk within these loci. This is the first step towards the long-term goal of constructing a genetic risk model for OC that allows for genetic testing and quantification of risk in individuals.

Rutgers Young Horse Teaching and Research Program: undergraduate student outcomes.

Equine teaching and research programs are popular but expensive components of most land grant universities. External funding for equine research, however, is limited and restricts undergraduate research opportunities that enhance student learning. In 1999, a novel undergraduate teaching and research program was initiated at Rutgers University, New Brunswick, NJ. A unique aspect of this program was the use of young horses generally considered "at risk" and in need of rescue but of relatively low value. The media interest in such horses was utilized to advantage to obtain funding for the program. The use of horses from pregnant mare urine (PMU) ranches and Bureau of Land Management (BLM) mustangs held the risks of attracting negative publicity, potential of injury while training previously unhandled young horses, and uncertainty regarding re-sale value; however, none of these concerns were realized. For 12 years the Young Horse Teaching and Research Program received extensive positive press and provided invaluable learning opportunities for students. Over 500 students, at least 80 of which were minorities, participated in not only horse management and training but also research, event planning, public outreach, fund-raising, and website development. Public and industry support provided program sustainability with only basic University infrastructural support despite severe economic downturns. Student research projects generated 25 research abstracts presented at national and international meetings and 14 honors theses. Over 100 students went on to veterinary school or other higher education programs, and more than 100 others pursued equine- or science-related careers. Laudatory popular press articles were published in a wide variety of breed/discipline journals and in local and regional newspapers each year. Taking the risk of using "at risk" horses yielded positive outcomes for all, especially the undergraduate students.

Rutgers Young Horse Teaching and Research Program: sustainability of taking a risk with "at risk" horses.

In 1999, the Young Horse Teaching and Research Program (YHTRP) was initiated at Rutgers University. The unique aspect of the program was using horses generally considered "at risk" and in need of rescue, but of relatively low value. The risks of using horses from pregnant mare urine (PMU) ranches and Bureau of Land Management (BLM) mustangs were high, but, ultimately, unrealized. No students or staff members were seriously injured over the course of the next 12 yr, and the horses were sold annually as highly desirable potential athletes or pleasure horses, usually at a profit. The use of "at risk" horses generated a significant amount of positive media attention and attracted substantial funding in the form of donations and sponsorships, averaging over $60,000 (USD)per year. Despite economic downturns, public and industry support provided sustainability for the program with only basic University infrastructural support. Taking the risk of using "at risk" horses paid off, with positive outcomes for all.

Supplementation of Ascorbic Acid in Weanling Horses Following Prolonged Transportation.

Though horses synthesize ascorbic acid in their liver in amounts that meet their needs under normal circumstances, prolonged stress results in low plasma concentrations due to enhanced utilization and renal excretion and can reduce immune function. It was hypothesized that plasma ascorbic acid could be maintained in weanling horses by oral supplementation following prolonged transportation. Weanlings were supplemented with no ascorbic acid (Tx 0: n = 4), 5 grams ascorbic acid twice daily for 5 days (Tx 1: n = 4) or for 10 days (Tx 2: n = 4) following >50 hours of transportation. Supplementation caused slight (P < 0.2) increases in plasma ascorbic acid concentrations. Both supplemented groups had decreased (P < 0.05) plasma concentrations for 1 to 3 weeks following cessation of supplementation, possibly due to increased renal excretion or suppressed hepatic synthesis. Supplementation of ascorbic acid following prolonged stress will increase plasma concentrations, but prolonged supplementation should be avoided.

Evidence-based equine nutrition.

One of the most difficult problems in equine nutrition research is often the lack of objective and clinically relevant end points. Nevertheless, this article attempts to present the best evidence (or lack thereof) for some of the most common clinical questions pertaining to such topics as the evaluation of glucose and insulin tolerance and factors that may confound results, dietary management of horses prone to laminitis and rhabdomyolysis, nutritional prevention of gastric ulcers and developmental orthopedic disease, the efficacy of commonly used herbal products, and feeding geriatric horses.

Beyond blood sugar: the potential of NMR-based metabonomics for type 2 human diabetes, and the horse as a possible model.

Metabonomic analysis is a powerful tool for identifying and characterizing metabolic disorders, for example type 2 diabetes and the metabolic syndrome. Nuclear magnetic resonance (NMR) spectroscopy is an essential tool for such analysis, with special benefits. The review assesses the current status and potential of NMR-based metabonomics of type 2 diabetes. The horse is proposed as a possible model for studying this condition and disease. Some examples are shown of horse blood analyses by NMR.

Insulin and glucose regulation.

Abnormally high or low blood glucose and insulin concentrations after standardized glucose tolerance tests can reflect disorders such as pituitary dysfunction, polysaccharide storage myopathies, and other clinical disorders. Glucose and insulin responses, however, are modified by the diet to which the animal has adapted, time since it was last fed, and what it was fed. Body fat (obesity), fitness level, physiologic status, and stress also alter glucose and insulin metabolism. Therefore, it is important to consider these factors when evaluating glucose and insulin tests, especially if only one sample it taken. This article describes the factors affecting glucose and insulin metabolism in horses and how they might influence the interpretation of standardized tests of glucose tolerance.