Building muscle for running depends on having sufficient protein in the diet of the appropriate type. The high-grain diets found in commercial feeds promote water retention within the muscle cells rather than good muscle function. Similar to humans who consume high-carbohydrate diets with inadequate exercise, the modern horse doesn’t move enough to warrant the high-grain diets it is fed. When fed lesser amounts than prescribed on the bag, the horse suffers vitamin and mineral starvation. This leaves the modern domestic horse looking plump, but moving with lethargy and often in pain. Many horses that appear to be "well filled out" are indeed muscle poor. When they are taken off the diets that promote water weight gain, they lose their plumpness and are left with atrophied muscles that were underneath the entire time.
When horses evolved, the food they ate played a role in how muscles evolved to match the environment in which they lived. When we consider feeding a horse to affect its muscles, we are aiming at affecting that brain and nervous system in a positive manner, which benefits the horse as much as it benefits the owner. Horses with muscle atrophy, either in specific places or overall muscle loss, have had damaging effects to their nervous systems.
Horses evolved to the animals they have become today from animals that originally were living in dense forests. Changes in the family Equidae occurred over a timeframe of 50 million years, transforming the small, dog-sized, forest-dwelling Eohippus into the modern horse. As grass began to appear the equids' diets shifted from foliage and fruits to grasses, leading to larger and more durable teeth and a change in their shape and size. With this change in teeth, their ability to digest their food changed. Their ancestors used the nutrients they found in grass and leaves they ate to build strong muscles for running, strong bones for carrying their bodies, lungs to enable them to maintain oxygen when running, and a digestive system that could ferment grass into proteins and not be permeable to neurotoxic infectious agents like fungus found in grasses. The ancestors of modern horses came in different sizes, and the first modern horses evolved from Mesohippus, an animal known for six grinding "cheek teeth", with a single premolar in front—a trait all descendant Equine still have.
Modern horses should eat grass and grass seed (a protein source) on a regular basis, however, many commercially prepared horse foods are grain based. When they are desperate for protein, modern domestic horses often will eat items like acorns, similar to the way horses might eat toxic plants when they are left with no other source of nutrition. These animals are responding to their nutritional needs in an environment where their needs are not being met. Because the musculoskeletal system is affected by the entire environment with which it interacts, we need to consider the horse’s external environment as a balance to its internal environment.
Many senior feeds on the market use primary ingredients such as beet pulp and wheat middlings. This makes the muscles appear larger but does not make them stronger, and when fed alone inhibits calcium absorption, a mineral necessary for muscle building. Beet pulp has too much calcium that imbalances other essential minerals and contains low levels of antioxidant vitamins A and E.
Building protein chains is one of the goals of the nervous system, in order to continue to communicate with the rest of the animal. Protein chains help to shape the animal as well as to communicate between systems. DNA is made up of protein. Muscles are made of protein. These structural components require mineral such as zinc, calcium, and phosphorus to do their job.
While horse breeds vary in size and shape, when we discuss nutrition in general, most horses’ muscles require about the same ratios of vitamins, minerals, proteins and fats.
Grains and grain products are high in Phytic acid, which inhibits zinc uptake. Modern soy products also have zinc-blocking mechanisms. Zinc is required for protein synthesis and also for DNA and RNA synthesis in body cells. Zinc accelerates the process of healing of wounds. These grains are also higher in omega-6 fatty acids, which produce fat rather than muscle, and provide different types of proteins than our horses’ ancestors utilized to evolve into the modern animal. Their ancestors ate seeds and plants high in omega-3 fatty acids, which are essential for brain development, muscle development, and also helped their prostaglandin systems to reduce inflammation when they were ill or wounded.
True grasses are among this group of plants: timothy, Bermuda, orchard, prairie and bluegrass. These are the types of plants horses consumed when they moved from the forest to the plains, and their teeth changed shape as they adapted to the change in diet. The seeds of these plants contain omega-3 fatty acids necessary for producing the “embryo” and seedlings to grow more plants. Thus horses have an ancestral need for consuming these types of plants. Integral to their diets is the consumption of a variety of plant materials including leaves, stems, seeds, flowers, buds and bushes. Browsing the rose bushes in the fall is a delicacy for many a horse looking for rose hips to supply essential fatty acids and vitamins. Omega 3 fatty acids are the building blocks for DNA and RNA as well as the protein chains that make muscle.
When feeding a horse that has muscle atrophy or overall muscle loss, it is important to pay attention to the type of protein the horse is eating as much as how much protein the horse is eating. Diets rich in grass, seed meals like canola, which is a hybrid plant, not a “Round Up Ready” plant, rice bran, which comes from the rice seed, and linseed which is flaxseed that has had the oil reduced makes a better balance of omega-3 fatty acids and ensures the animal is obtaining enough omega-3 fatty acids along with balanced essential vitamins needed like A, the B’s and minerals like calcium, zinc, phosphorus. It also helps to develop muscles as they heal. When using omega sources it is important to balance in favor of more omega-3 than omega-6. A mix of linseed and rice bran at a 3 to 1 ratio will yield a feed that favors omega-3 to omega-6 fatty acids.
Without the use of any drugs, it is possible to restore muscles that have atrophied. I always suggest a visit from your AVCA certified Animal Chiropractor to restore nerve function. In order to allow the horse to reduce inflammation and maintain nerve function it is important to feed the correct amounts of omega fatty acids, vitamins and minerals.