Retirement risk factors, exercise management and muscle mass in US senior horses

Background: Information on the management and health of US senior horses (≥15 years of age) is currently limited. Objectives: Provide information on (1) primary use of US senior horses, (2) reasons and risk factors for horse retirement, (3) exercise management, (4) prevalence of low muscle mass and (5) risk factors for, and owner-perceived consequences of, low muscle mass. Study design: Online survey. Methods: Survey responses from 2717 owners of U.S.-resident senior horses (≥15 years of age) were analysed descriptively and inferentially, using ordered and binomial logistic regression, ANOVA and the Kruskal–Wallis test. Results: The most frequently reported primary uses were pleasure riding/driving (38.5%) and full retirement (39.8%). Most horses (61.5%) were retired between 15 and 24 years of age, with health problems being the main reason. Age, female sex, Thoroughbred breed and various medical conditions were identified as risk factors for retirement. In working horses (i.e., those not retired or semi-retired), exercise intensity was negatively associated with age. The owner-reported prevalence of low muscle mass in all horses was 17.2% (95%CI = 15.7–18.7). In those affected by low muscle mass, the ability to work and welfare-related aspects were commonly perceived to be impaired. Increasing age, sex (gelding), pituitary pars intermedia dysfunction, osteoarthritis, laminitis and primary use (retired and semi-retired vs. use for competition) were identified as risk factors for owner-reported low muscle mass. Main limitations: Potential response, recall and sampling bias. Causal relationships cannot be established. Conclusions: Although structured exercise into old age may provide health benefits (as seen in elderly people), a large proportion of horses were fully retired in the current study. Senior horses were mainly retired for health problems and characterising these problems may aid in extending their work/active life. Low muscle mass was perceived to affect horses' welfare and ability to work, and identification of prevention and treatment strategies is therefore warranted.