Knowing your horse’s bodyweight is essential for determining the best nutrition plan to keep him healthy.
By Dr. Jyme Nichols, Bluebonnet Feeds; Photos Courtesy of Bluebonnet Feeds
Most horse owners and veterinarians underestimate bodyweight when using only visual assessment. A livestock scale is the most accurate method for determining your horse’s weight, but it’s not easily accessible by most horse owners. This poses two questions for horse owners:
- Is it really that important to know your horse’s bodyweight?
- Without having access to a scale, are there other ways to make an educated estimate of bodyweight?
Here’s what you need to know.
Understanding Bodyweight
Bodyweight is the single most important factor needed for establishing a nutrition program for any horse. Nutrient requirements set forth by the National Research Council are based on bodyweight, therefore you must have at least a general idea of your horse’s bodyweight to determine the appropriate set of nutrient requirements he requires. Bodyweight is correlated with nutrient requirements and total feed intake; larger horses have higher nutritional requirements and must consume more total food than smaller horses.
Understanding bodyweight is also important when it comes to following label guidelines for feed. Many horse owners don’t consult with a nutritionist when choosing a feed program and must rely on the feeding instructions provided by a feed manufacturer. These instructions are required by law to be listed either on the bag or on an attached tag. Each manufacturer may list instructions in a slightly different format, but they’re always based on bodyweight.
For example, one feed tag may instruct to feed 0.5 pound for every 100 pounds of bodyweight. Another may instruct to feed 0.5 percent of bodyweight. For both examples, that would mean feeding 5 pounds per day if your horse weighs 1,000 pounds. However, if you underestimated your horse’s bodyweight, and he actually weighs 1,250 pounds, your horse should have been fed 6.25 pounds per day. If you overestimated bodyweight and your horse actually weighs 800 pounds, he should’ve been fed 4 pounds per day.
In the case of underestimating your horse’s bodyweight and feeding too little, your horse can end up in a negative energy balance, meaning he’ll begin to lose weight and drop in body condition. If you overestimate your horse’s bodyweight and feed too much feed, he’ll begin to accumulate excess fat and become overweight or obese. Both situations can have negative effects on the health and performance of your horse.
Estimating Bodyweight Without a Scale
While a scale is most accurate, it’s not always most practical. Several systems have been established to help you estimate bodyweight.
The most convenient and inexpensive option is a weight tape, which estimates bodyweight based on circumference of the heart girth. However, this is the most inaccurate method. A 2002 study by Ellis and Hollands evaluated the accuracy of four weight tapes on 2,000 horses, including 112 different breed types, and found significant differences among the tapes.
A preferable method for estimating your horse’s bodyweight is the use of calculations that consider both heart girth and length of the horse as shown on page 114. Additionally, consider your horse’s body-condition scoring, neck circumference, and girth-to-height ratio.
The Henneke body-condition scoring system, based on a 1–9 scale, is the gold standard in evaluating body fat. It evaluates specific areas of fat accumulation, seen at right.
Although body-condition score has been an industry standard, it’s a subjective system and isn’t especially useful in differentiating areas of regional adiposity that may be indicative of disease. For example, heavy fat deposits along the crest of the neck are associated with altered metabolic states such as insulin resistance. A standardized 0–5 cresty-neck scale developed by Carter et al. (2009) is a subjective scoring system developed to help assess regional fat deposits that may indicate health concerns.
Girth-to-height ratio (G:H) is another useful tool in assessing proper body condition in horses and is similar to body mass index (BMI) in humans. For this assessment, a measurement of the heart-girth circumference is divided by height. Horses are considered overweight if the G:H ratio is greater than or equal to 1.26 and obese if the ratio is greater than or equal to 1.29. Ponies are considered overweight and obese at G:H ratios greater than or equal to 1.33 and 1.38, respectively.
The Result = Healthy Horses
Horses that are managed at their optimal healthy bodyweight can lead longer, healthier, happier lives and be less likely to suffer from various metabolic diseases and possibly career-ending performance-related injuries.
With tools such as weight tapes, bodyweight calculations, body-condition scoring, cresty-neck scoring, and girth-to-height ratios, even horse owners who don’t have access to a weight scale are capable of maintaining proper bodyweight and condition of their horse.
ABOUT THE AUTHOR
Dr. Jyme Nichols grew up on a cattle ranch in the northern Nebraska sandhills. She’s been involved with horses and agricentire life. Dr. Nichols, an ARPAS-certified Professional Animal Scientist (PAS) in the equine discipline, has been presented with research awards from the Equine Science Society and the American Society of Animal Science.