There is no missing it when a horse ties up, or even has a severe localized muscle injury, but generalized muscular dysfunction is more difficult to recognize and can cause significant pain, poor performance, gait and/or behavioral issues.
Sustained daily work at anything faster than a walk requires conditioning and muscular adaptation
The horse is equipped with remarkable athletic ability which supports traveling long distances to find food and occasional bursts of speed to evade predators. However, when we impose regular exercise more demanding than a walk the muscle must ramp up its capacity to support that work.
In the normal course of a conditioning program, as work progressively increases the muscle is stressed. In response to the stress, the muscle adds protein leading to more bulk and definition. Antioxidant defense systems and cellular energy generating equipment (enzymes and mitochondria) are increased.
Signs of poor adaptation include poor bulk or even obvious loss of muscle mass and high resting muscle tone. Healthy muscle is pliable and feels like a beef roast. At rest, the chest and muscles above the elbow and stifle will be softest. Muscle should not tense up when you palpate it. If you run a hoof pick or capped pen down the back the horse should dip, not brace against it. Unexplained gait abnormalities could be neurological but could also be muscular. Young “colt sore” racehorses in training often have a large muscular component to their discomfort.
Materials to respond to training stress must come from the diet. Total protein quantity may be sufficient but key amino acids inadequate. L-leucine is the most abundant amino acid in muscle, also an important energy source and its metabolite HMB stimulates muscle growth. Other key amino acids include:
- L-Glutamine – bulk and the antioxidant Glutathione
- L-Arginine – synthesis of Creatine, a high energy storage form, and nitric oxide, a vasodilator and growth stimulant
- L-Carnitine – an amino acid derivative needed to carry fats into the mitochondria to be burned and its metabolite Acetyl-L-Carnitine which regulates carbohydrate use for energy and is an antioxidant.
- Beta-alanine – another amino acid derivative that supports the synthesis of Carnosine, a buffer of acids that are responsible for muscle pain and fatigue
Both individual amino acids and high quality protein sources like Whey can be used to support muscle bulk and function.
Inadequate magnesium intake can cause muscle cramping, twitching, and even gait abnormalities. It maintains normal levels of muscle excitability and is required for energy storage and utilization in the cell. The electrolyte minerals are also critically important as they regulate contraction, relaxation and nerve conduction.
Horses under training stress often benefit from adaptogenic herbs. Adaptogens may assist the body in maintaining appropriate levels of stress hormones in response to exercise. Jiaogulan, Rhodiola and Ginsengs are examples of adaptogens.
When the need to generate energy is high, vitamin nutrition becomes critical and requirements increase. The normal processing of amino acids/proteins, carbohydrates and fats relies on adequate vitamin intake. Vitamins are also co-factors in the synthesis of key metabolites in hard-working muscle.
Helping your horse be the best athlete he can be requires meeting the unique nutritional needs of exercise. The results can be truly spectacular.
Eleanor Kellon, VMD