Nutrition and the Equine Topline

Most forages provide plenty of total protein for a mature horse in work; however, some forages, such as alfalfa, provide a higher quality of protein than others.

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Q. My 14-year-old Warmblood is in consistent upper-level dressage training, working hard three or four days a week in the arena and getting in an additional hack day per week on the trails. His coat doesn’t quite have the "bloom" I’d like it to (it’s a bit dull and course) and his topline isn’t quite as developed as I think it should be for his level of work. Is his topline possibly a nutrition rather than a training problem?


A. This is an issue I see fairly often in sport horses when out in the field doing farm calls. It can be a little difficult for some owners to put their finger on because at first glance it looks like perhaps the horse needs more weight, but when you assess the six areas of the body while performing a Hennecke body condition evaluation, you realize that actually the horse has enough fat cover over the ribs and often through the neck. The issue is that they lack topline muscling through the loin and sometimes in the saddle area and over the rump towards the tail. Adding more calories to the ration as you would for a horse that is truly underweight would likely just result in a fat horse.

The problem is less one of inadequate calories and more likely an issue of inadequate quality protein. It is very unusual for me to come across a ration with inadequate crude protein. Nearly all mature working horse’s rations are meeting their crude protein requirements, but in reality horses do not have a protein requirement they have an amino acid requirement. Amino acids are the units that make up proteins. Some of them are essential, meaning that they must be present in the diet, because the horse cannot make them itself. Others amino acids are non-essential, meaning that while they can be in the diet, the horse can actually make them too.

Amino acids are expensive to quantify in feed, and we don’t know exactly what the horse’s amino acid requirements are. The Nutrition Research Council does have an estimate for the amino acid lysine, but not for any other amino acids—the assumption being that as protein provides a broad range of amino acids, and amino acid requirements will be met if the crude protein requirement it met.

“Protein quality” is the protein proportion that’s made of essential amino acids. Therefore, a protein that provides a greater amount of essential amino acids is a higher quality protein than one that provides less. Most forages provide plenty of total protein for a mature horse in work; however, some forages provide a higher quality of protein than others. Protein quality might drop with maturity at cutting, and if indigestible fiber is high it might bind the protein, making it less available during digestion.

Legumes like alfalfa tend to have a better amino acid profile with more lysine than grass hays. Lysine is an essential amino acid that is often referred to as the limiting amino acid. A limiting amino acid is an essential amino acid that tends to limit protein synthesis because the amount of this amino acid in the diet is limited.

Protein synthesis is a process where RNA essentially calls out for specific amino acids and joins them together in a predetermined order that will result in the formation of a specific protein. It is a bit like making words in a sentence with the letters in the alphabet being amino acids with vowels being essential amino acids and consonants being non-essential amino acids and each word being a protein. If you were limited to having only three letter Es you would not be able to make many words. Once you had used up that third E the next time you needed an E and didn’t have one your word building would be over even though you might have lots of extra As and Ls etc. The same concept applies to protein synthesis. If you run out of lysine or any other essential amino acid your ability to create new protein is reduced until you consume more of the needed essential amino acid. This results in a less than optimal scenario for building proteins. Given that proteins are the basis of collagen, elastin, keratin, and muscle fibers, as well as hormones, enzymes, antibodies, etc., having adequate essential amino acids is crucial.

The fact that your horse has poor muscling over the topline as well as a dull coat could indicate the need for a source of higher quality protein in the diet. It is also important to remember that poor coat and lack of muscling can also be a symptom of gastric ulcers, so it’s always wise to have your horse looked at by a vet to rule out any underlying issues that might not be diet-related.

Another consideration for your veterinarian is the possibility of a vitamin E deficiency, as levels in hay are low and individual utilization of vitamin E varies by horse. A deficiency can be detected through blood work and could impact ability to develop good topline. Other issues that could prevent topline formation include conditions such as polysaccharide storage myopathy, joint or dental discomfort, problems with saddle fit, and shoeing errors.

Assuming the issue is protein quality, you need to add a source of better quality protein. Protein quality of pastures in spring and summer tends to be very good, so turnout is one option. However in winter, or if turnout would lead to undesirable weight gain, replacing up to a third of the horse’s current forage ration with alfalfa might help.

Another option is to utilize a high-protein ration balancing feed. These feeds tend to use soybean meal as a major protein source because it has the best amino acid profile of most of our plant-based feed ingredients. One ration balancer benefit is that it’s also highly fortified in trace minerals and important vitamins that can be lacking in your forage. The serving size is typically small—about 2 pounds per day for an average sized horse—and therefore doesn’t contribute a major source of calories. Most major feed manufacturers have a ration balancer—ask your feed store.

If you are already feeding a balanced diet with a source of additional vitamins and minerals, you might prefer to utilize an amino acid supplement rather than a ration balancer. Several such products exist on the market. Those that are beneficial to muscle development tend to provide amino acids from whey protein, which is highly bioavailable.

With improved protein quality in the diet and correct work I would expect you to see an improvement in overall topline development, as well as hair coat quality, in about four to six weeks.

Do you have an equine nutrition question? Thunes and The Horse’s editors want to hear from you! Send your questions to Editorial@TheHorse.com.

About the Author

Clair Thunes, PhD

Clair Thunes, PhD, is an independent equine nutrition consultant who owns Summit Equine Nutrition, based in Sacramento, California. She works with owners/trainers and veterinarians across the United States and globally to take the guesswork out of feeding horses. Born in England, she earned her undergraduate degree at Edinburgh University, in Scotland, and her master’s and doctorate in nutrition at the University of California, Davis. Growing up, she competed in a wide array of disciplines and was an active member of the United Kingdom Pony Club. Today, she serves as the regional supervisor for the Sierra Pacific region of the United States Pony Clubs. As a nutritionist she works with all horses, from WEG competitors to Miniature Donkeys and everything in between.

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