Estimating actual and ideal bodyweight of adult horses
There is a growing problem in the United States of overweight and obese horses. Excess bodyweight can lead to many health issues including insulin resistance, Equine Metabolic Syndrome (EMS), laminitis, poor thermo-regulation, and decreased athletic ability.
Determining a horse’s bodyweight is important for weight and health management; however, few owners have access to a livestock scale. Equations exist that utilize horse height and body length and allow horse owners to predict horse bodyweight in the absence of a scale.
New improved equations have been developed that add breed type and neck and girth circumference to height and body length to more accurately predict bodyweight for ponies, Arabians, stock-type horses, draft horses and warmbloods.
Materials and methods
In 2011, body measurements were taken on 629 adult horses and ponies at two horse shows in St. Paul, Minnesota (WSCA Champ Show and State 4-H Horse Show). In 2014, the same measurements were taken on 227 adult draft and warmblood horses at the Scott County Fair Draft Horse Show (Jordan, Minnesota), and the Fall Harvest Horse Show (St. Paul).
The WCSA Champ Show and the State 4-H Horse Show featured primarily Arabians, ponies, and stock-type horses. The Scott County Fair Draft Horse Show was exclusively draft horse teams and the Fall Harvest Horse Show was a Hunter/Jumper show attended by primarily warmblood horses. At all shows, data was collected on adult horses that were 3 years old and older and not pregnant.
Figure 1. Body measurements including neck circumference located halfway between the poll and the withers (N), height at the third thoracic vertebra (H), girth circumference at the third thoracic vertebra (G) and body length from the point of the shoulder to a point perpendicular to the point of the buttock (L) were taken on all horses.
The following body measurements were taken by trained personnel: body condition score (BCS) on a scale of 1 (poor) to 9 (extremely fat), height at the third thoracic vertebra, neck circumference at the midway point between the poll and the third thoracic vertebra, body length from the point of the shoulder to a line perpendicular to the point of the buttock, and girth circumference at the third thoracic vertebra (Figure 1).
Each horse was weighed using a portable livestock scale. Age, gender, breed, and discipline were also recorded. For draft horses only, shoe height was measured and actual height (height minus shoes) was used in the calculations. At the draft horse and warmblood show, the horse’s exhibitors were also asked to estimate their horse’s bodyweight prior to weighing horses on the livestock scale. These estimates of bodyweight were later compared to actual bodyweight.
Body measurements were different between breed-types (Table 1). Ponies and draft horses had higher BCS compared to the other breed types. Almost half (42%) of draft horses; 14% of the stock horses, ponies and Arabians; and 2% of warmbloods were considered overweight with a BCS greater than or equal to 7. On average, draft horse and warmblood owners and handlers were 115 pounds off their horse’s actual bodyweight. Misjudging horse bodyweight by this amount could have serious implications for nutrition and health management.
Table 1. Average age, body condition score (BCS), body measurements (in inches), and bodyweights (in pounds) of different breed types of adult horses. Total = number of horses in each group.
New equations to estimate bodyweight
Arabians, stock horses, and ponies
Bodyweight (lbs) = [girth (in)1.486 x body length (in)0.554 x height (in)0.599 x neck (in)0.173] / X
X = 119 (Arabians), 119 (ponies), or 114 (stock horses)
Draft horses and warmbloodsBodyweight (lbs) = 25.09 x [girth (in)1.528 x length (in)0.574 x height (in)0.246 x neck (in)0.261] / X
X = 1,181 (draft horses) or 1,209 (warmbloods)
New equations to estimate ideal bodyweight
Arabians, stock horses, and ponies
Ideal bodyweight (lbs) = [(15.58 x height (in)) + (23.52 x body length (in)) - X]
X = 1,344 (Arabians), 1,269 (stock horses), or 1,333 (ponies)
Draft horses and warmbloods
Ideal bodyweight (lbs) = [(27.55 x height (in)) + (25.98 x body length (in)) - X]
X = 2,092 (draft horses) or 2,235 (warmbloods)
When ideal bodyweight was estimated for each horse and subtracted from the scale bodyweight, the difference in pounds between each BCS averaged 37 for stock horses, 22 for ponies, 33 for Arabians, 86 for draft horses, and 37 for warmbloods.
To remove the technical barriers that may inhibit some horse owners and professionals from utilizing the new bodyweight-related equations, a fee-based app, Healthy Horse, is available for use with Android (Google Play) and Apple (iTunes). The app estimates bodyweight and ideal bodyweight for different horse breeds after users enter body measurements.
These projects were funded by USDA-NIFA and Purina Animal Nutrition, LLC.