Clients often bring horses to our veterinary practice with a complaint of weight loss. In my approach, I start by determining whether the horse is really underweight. Whenever I think about changes in body weight, there is a specific thought process I use to identify the reasons for it. This approach is based on an understanding of the balance between a given horse’s energy intake and energy output. Keeping this in mind, I look at all of the factors that contribute to nutrition and intake on one hand, and energy expenditure on the other.
By understanding this important balance and the factors that affect it, keeping horses at optimal weight and health is easier and more intuitive and, in cases of weight loss, can be better understood and resolved.
BODY CONDITION SCORING (BCS)
In order to determine whether a horse is underweight or not, it is first important to know what their optimal weight should be. This is a very subjective assessment. The closest we can come to making an objective judgment is through an established Body Condition Score System, which rates horses on a scale of 1-9. On this scale, 1 is emaciated and 9 is obese. Body condition scores of 5 to 6 are considered optimal. This system is based on assessment of the muscle and fat that cover of the bony landmarks of the body, especially of the top-line and ribs.
Information on body condition scoring is readily available on the Internet, and I recommend that horse owners familiarize themselves with it and use it. Scales for horses are generally not easily accessible. Weight tapes measure the circumference of the girth and relate that to weight. They are a cheap and practical alternative to a scale and are especially valuable for tracking change. For the purposes of this article, I consider significant weight loss to be a state where horses fall out of the optimum range (5-6) of Body Condition Score System.
WEIGHT LOSS
Weight loss results from an imbalance between caloric intake and expenditure of energy. Factors that affect either or both intake and outflow will change the balance and affects a horse’s weight. If there is more energy expenditure than caloric intake, then a horse will lose weight.
Let’s first discuss expenditure of energy. How much energy a horse expends depends first upon the amount of energy needed for maintenance. This depends on body weight and metabolic rate. Different breeds and individuals have varying basic nutritional needs for maintenance. The amount of feed necessary for maintenance of a typical “hotblood” like an Arabian or Thoroughbred tends to be greater (per unit body weight) than that for a typical “coldblood” like a draft or pony breed. Beyond energy for maintenance is that needed for additional body functions including:
Weight loss results from the breakdown and conversion to energy of complex sugars, muscle, and fat from the body. This breakdown is intricately controlled by a complex system of chemical messengers responding to the body’s perceived needs. Expenditure of energy must be balanced by energy intake in the form of nutrition, or signals are sent to start to break down the body’s stores of complex sugars, muscle, and fat to account for the difference in needed energy, resulting in loss of these tissues and weight loss.
Nutritional intake is how much nutrition is brought into the circulation from the intestine, and this relates to what is taken into the body from the diet. There are several steps that are critical for a horse to achieve necessary nutritional intake. A horse must have access to and ingest an adequate amount of high quality feed of the appropriate type. He must be able to process this by proper grinding of feed by the teeth. Poor dental function results in poorly processed feed, which is not well digested and absorbed in the intestine. A healthy gut assimilates the needed nutrients into the bloodstream.
Healthy body systems and metabolism results in the nutrients in the bloodstream being processed, with the necessary energy used and the remainder put into body stores in the form of complex sugars, muscle and fat. Anything that decreases nutritional intake, with all else being equal, will result in weight loss. Therefore, the most common reasons for weight loss in horses are:
MANAGEMENT & FEEDING SUGGESTIONS
Start by being able to define your horse’s body condition using the Body Condition Scoring System. Keep in mind that it is more difficult to assess body condition in the winter, when hair-coats are long. Feel your horse’s body, especially his top-line and ribs, through the thick coat to get a better assessment.
When designing a feeding program, keep in mind the basic metabolic differences among breeds and individuals. A young Thoroughbred race horse will be a much “harder keeper” than a 10 year old Pony gelding. Within breeds, certain individuals will be harder keepers than others. The basis of most equine feeding programs is good quality forage or hay. Many idle horses without special needs maintain their weight well on grass hay alone. For others, it will be necessary to account for extra needs when calculating the feed necessary for a given horse.
Think of the feed needed for maintenance, then add in additional feed to account for these additional factors. For horses that have needs beyond maintenance, additional energy rich concentrates (grains) and other special feeds may also need to be added. Calorie-rich supplements like corn oil or rice bran may be added as recommended by your veterinarian. There are now many commercial diets available for horses with almost any special need.
CONCLUSION
Maintaining optimal weight and preventing weight loss in horses requires a balanced approach. Your veterinarian can help you take into account all of the factors we have discussed to arrive at an effective management program for your horses. I feel that the best way to accomplish this is through annual or semi-annual veterinary visits and consultation.
By Douglas O. Thal DVM Dipl. ABVPBoard Certified in Equine PracticeThal Equine LLCLast Updated August 20119:00 am - 12:00 pm
1:00 pm - 5:00 pm
9:00 am - 12:00 pm
1:00 pm - 5:00 pm
9:00 am - 12:00 pm
1:00 pm - 5:00 pm
9:00 am - 12:00 pm
1:00 pm - 5:00 pm
9:00 am - 12:00 pm
1:00 pm - 5:00 pm
9:00 am - 12:00 pm
Closed Sundays & Holidays