When it comes to weight problems, we are more likely to be concerned about the overweight horse. But the underweight horse can be just as troubling. To solve the problem, the common approach is to add more calories. But hold your horses! (Pun intended.) We must first determine the reason your horse is underweight in the first place.
Start with the teeth
Dental problems can be easy to miss. Watch to see if your horse is chewing with his mouth open or dropping partially chewed food. He may also not finish his meals or salivate excessively. Or he may begin tossing his head.
All horses should have a dental exam every year to check for points or infection. Older horses may have loose teeth or excess molar wear making it difficult to chew their hay. For these horses, I recommend wetting their feed and offering a chopped forage (preferably one without molasses) that is available ‘round the clock.
Next, make sure your horse’s liver is functioning well
The liver plays a key role in digestive health, metabolism, and cleansing the blood from toxins. Any disruption in its function could cause your horse’s appetite to decline and contribute to weight loss.
This vital organ contributes to health in a variety of ways:
- Production of bile. The horse relies on bile to start fat digestion. Bile also aids in detoxification.
- Fat metabolism. Fat is processed in the liver to make is useful to the body’s tissues.
- Synthesis of blood proteins. These are necessary for water balance, as well as for transporting minerals to tissues.
- Storage of nutrients. These include the fat-soluble vitamins (A, D, E, and K) as well as B vitamins, minerals, and glycogen (storage form of glucose).
Test your horse’s blood yearly to see how he’s doing on the inside.
Your veterinarian is the best resource for interpreting the blood test results, but some tests include[i]:
- If low, it can indicate liver disease. But can be reduced due to other causes such as low protein intake.
- Gamma Glutamyl Transferase (GGT). Elevated levels can indicate a problem. But it can also be high if the horse is insulin resistant or has equine Cushing’s disease (PPID). When accompanied by high ALP (alkaline phosphatase), it is a better indication of liver dysfunction.
- Lactic Dehydrogenase (LDH). This enzyme can be compared with other blood enzymes to diagnose liver dysfunction.
- Other indicators include elevated bilirubin, and liver enzymes such as ALT and AST, but your vet can help you interpret these.
Pay attention to encysted larvae
Horses that don’t look or feel well, despite a good diet, may be suffering from too many encysted larvae. The larvae of small strongyles can become encapsulated and burrow into the gut wall, impairing nutrient absorption, leading to weight loss and malnutrition.
Examining a fecal sample will not reveal these larvae. Consequently, I recommend deworming once a year with either a double dose of fenbendazole for five days (Panacur PowerPac), or a yearly administration of moxidectin. Both will remove encysted larvae.
The hind gut microbiome is critically important
The microorganisms in your horse’s hind gut (cecum and large colon) are responsible for producing enzymes capable of digesting fibers. Hay and pasture grasses are mostly fiber and for your horse to derive calories from them (and hence, gain weight), the health of his hindgut microbiome must be in top shape.
A healthy microbiome boosts immune function by protecting against environmental viruses and bacteria.
To boost microbial health:
- Add Prebiotics. Prebiotics feed the existing beneficial bacteria, making them better at producing enzymes to digest fibers. Typically, they are in the form of fructo-oligosaccharides (FOS) or mannooligosaccharides (MOS). Yeasts such as Saccharomyces cerevisiae and S. boulardii are often combined with MOS to boost the overall health of the microbial flora.
- Avoid too much starch. Digestion of starch and sugar leads to negative by-products and endotoxins, potentially causing colic, cecal acidosis, and laminitis.
Feed a diet high in Mcals
In horse nutrition, we use Mcals (mega calories) as a unit of energy. Fat has more than twice the number of Mcals as carbohydrates and proteins, making it an excellent choice for putting on weight.
Good fat choices are:
- Oils that are high in omega 3s such as flaxseed oil or camelina oil.
- Hemp seed oil – contains gamma linolenic acid (GLA) which reduces inflammation. But there are more omega 6s then 3s, so another source of omega 3s is necessary (such as chia seed or flaxseeds)
- Coconut, rice bran, or corn oils – but keep in mind that they do not provide omega 3s, so another fat source must be added to the diet.[ii]
Stay away from soybean oil, or soy protein products, unless they are organic.
Combine high protein with fat to boost overall health while adding Mcals:
- Hemp seed hearts – these are by far the best way to add extra fat, while offering your horse the best quality plant protein available.[iii]
- Ground flaxseeds or chia seeds – similar in their omega 3 content and provide protein.
Keep in mind that if your horse has liver (or kidney) disease, protein intake needs to be reduced.
- Alfalfa hay, cubes, or pellets. These are higher in protein and Mcals than grass forages.
- Beet pulp. This is mostly water-soluble fiber that is digested in the hindgut, providing additional Mcals. If possible, go with a non-GMO version.
- Coconut meal. Provides protein but it is not high in quality.
- Soybean meal. Unless organic, it is best avoided since most soy grown in the US is sprayed with RoundUp herbicide (glyphosate).
Keep your horse warm during winter
An underweight horse usually requires a blanket during wintry weather. A blanket will help reduce the amount of Mcals burned to maintain a normal body temperature.
Finally, make certain that your horse has access to forage. This can be hay and/or pasture. It must be always available, 24/7, all day and all night. Fiber fermentation within the hindgut results in heat production. A steady flow of forage throughout the digestive tract will protect his health in other ways, as well. By respecting this fundamental truth about horses’ needs, your horse will not only stay warm, but you’ll prevent ulcers, inflammation, and other stress-related disorders.
For the underweight horse, don’t just reach for extra feeds. Conditions such as poor teeth, liver dysfunction, and compromised hindgut microbiome can impact your horse’s ability to maintain a good weight. Consider the whole horse when helping him regain his health.
[i] Test for Liver Disease: https://www.equisearch.com/HorseJournal/test-for-liver-disease
[ii] Getty, J.M. Your horse has a question – Are you feeding me omega 3s everyday? https://gettyequinenutrition.com/pages/your-horse-has-a-question-are-you-feeding-me-omega-3s-every-day
[iii] Getty, J.M. Choose hemp instead of soy. https://gettyequinenutrition.com/pages/choose-hemp-instead-of-soy
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Juliet M. Getty, Ph.D. is an independent equine nutritionist with a wide U.S. and international following. Her research-based approach optimizes equine health by aligning physiology and instincts with correct feeding and nutrition practices. Dr. Getty’s goal is to empower the horseperson with the confidence and knowledge to provide the best nutrition for his or her horse’s needs.
Dr. Getty’s fundamental resource book, Feed Your Horse Like a Horse, is available in paperback and Kindle versions. The paperback version is available at https://gettyequinenutrition.com — buy the book there and have it inscribed by the author. Print and Kindle versions are also available at Amazon; find print versions at other online retail bookstores. The seven individual volumes in Dr. Getty’s topic-centered “Spotlight on Equine Nutrition” series are available with special package pricing at her website, and also at Amazon in print and Kindle versions. Dr. Getty’s books make ideal gifts for equestrians!
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