It's no secret that equine obesity is a growing problem. But what makes some horses more likely to be overweight than others, and just how many horses could stand to lose some weight? A team of British researchers set out to answer those questions in a recent study.
An obese or overweight horse is at risk for certain health conditions such as insulin resistance and laminitis. And, due to the subjective nature of determining how much fat horses have on their bodies, owners tend to underestimate body condition scores. Thus, the actual prevalence of obesity in the equine population remains fairly unknown.
To better enumerate the obese equid population in Great Britain and identify possible risk factors for obesity, Charlotte Robin, a research assistant at the Animal Health Trust in Newmarket, England, and colleagues randomly selected 792 owners of horses and ponies registered with 30 veterinary practices in Great Britain to complete a questionnaire by mail during a two-year study.
Owners were asked to estimate their horse's or pony’s body condition score (BCS) based on a modified version of the Carroll and Huntington scoring system, which evaluates the equid’s fat cover based on a scale ranging from zero (very thin) to six (very fat). The researchers categorized the horses and ponies as obese if the owners scored them a five or six.
Upon reviewing their results, the team found that:
- Approximately one third of the owners that responded owned ponies and two thirds owned horses;
- The average age of study equids was13 years;
- About 62% of equids were used for pleasure riding, 18% for competition, and 20% for nonriding purposes, such as breeding or retirement.
- The majority were turned out for part of the day and stabled for the remainder;
- Pasture turnout time increased during the spring and summer months; and
- 86% received supplemental feed aside from forage, but that percentage varied seasonally—91% received grains or concentrates in the winter and 79% did in the summer.
Obesity-related findings included:
- Owners scored about 31% of horses and ponies in the study as obese:
- 41% of ponies and 26% of horses included were considered obese;
- 34% of animals between 5 and 20 years old were obese, compared to 20% of those younger than 5 and 25% of those over 20;
- Overall, 16% of study horses reportedly had suffered at least one previous episode of laminitis; however, 21% of obese horses and ponies had a history of laminitis compared to only 13% of those that were in good or underweight condition.
Preliminary analysis revealed that several individual horse and management factors (such as breed, height, ease of weight maintenance, turnout, feeding practices, and exercise regimen) appear to impact a horse's obesity risk. The researchers then looked at data from 785 animals in a multivariable model and identified the following risk factors for obesity:
- Breed—Draft horses, cobs, Welsh ponies, and other breeds native to the United Kingdom had a higher incidence of obesity compared to Thoroughbreds.
- Easy keepers—Horses considered easy keepers were more likely to be obese than those that maintain appropriate weight easily or those considered hard keepers.
- Use—Pleasure riding and nonriding animals had a higher incidence of obesity compared to those used for competition.
The breed differences, especially with native breeds, could represent a genetic adaptation to the sparse, poor-quality forage that grows in their normal environment, the team said.
“Native breeds may be genetically better adapted to survive in harsh conditions, having a so-called thrifty genotype, increasing their risk of obesity when maintained in an environment where food is of better quality and more readily available,” Robin explained.
It is also possible that some horses and ponies could have a genetic predisposition for obesity and maintaining weight easily, similar to results found in human research, the team said.
“Competition horses are likely to be managed in different ways compared to noncompetition or nonridden animals, and this may also contribute to the reduced risk of obesity within this subpopulation,” Robin added. More exercise and better fitness levels in competition animals could help reduce the chance of a horse becoming obese by both improving insulin sensitivity and burning fat. She also noted that competition horses also tended to be younger than those used for pleasure riding or not ridden.
Considering both horse and management risk factors for obesity identified by this study, owners and veterinarians can implement strategies to reduce obesity in the equine population. Owner awareness and education on high-risk breeds, ease of maintaining weight, and exercise practices is key to assessing their own animals and management techniques.
The study, "Prevalence of and risk factors for equine obesity in Great Britain based on owner-reported body condition scores," will appear in an upcoming issue of theEquine Veterinary Journal. http://www.ncbi.nlm.nih.gov/pubmed/24735219