The key is not only how much protein is in the ration, but above all its quality, that is, the content of key amino acids such as lysine, methionine and threonine. These are essential amino acids, which the horse cannot synthesise itself. They are what allow muscle to be built properly, recovery after work to take place, and young horses to develop in a healthy way. The higher the content of limiting amino acids (especially lysine), the better the body will use the feed.
A protein shortfall usually does not produce sudden signs, but builds gradually. Horses that receive too little often struggle to build muscle despite regular training, and their coat becomes dull and is slower to shed. Recovery after work takes longer, and the muscles may be more sore. In young horses, growth can slow and muscle and bone may develop less well. Shortfalls occur not only in sport horses, but also in older horses, nursing mares and those fed poor-quality forage, especially in winter, when access to fresh, nutritious fibre is limited.
On the other hand, too much protein is just as undesirable, and it happens even more often. When the body receives too much protein, the kidneys have to work hard to get rid of the excess nitrogen. What appears then is characteristic ammonia-smelling sweat, wet bedding in the stable and large volumes of urine. Too much protein can also make the air in the stable less comfortable to breathe because of the smell of ammonia, and in young horses it can lead to growth disturbances if the diet is not properly balanced. Most importantly, surplus protein has to be broken down and excreted, which demands intensive work from the metabolic system and places a burden above all on the kidneys and the liver.
When judging whether a horse is receiving the right amount of protein, it is worth watching its condition, muscling and behaviour after training carefully. Hay quality, the share of lucerne in the diet, the composition of the concentrate and the overall ratio of energy to protein in the ration are decisive. Remember that in sport horses a rise in energy requirement does not go hand in hand with a rise in protein requirement. Harder work increases energy needs substantially, whereas protein needs rise only slightly. That is why an excess of protein often occurs in the diet of sport horses. If, despite being in work, the horse is not building muscle, or on the contrary sweats excessively and its sweat or urine smells very strong, that is a sign that the feeding is worth a closer look and the ration worth discussing with a nutritionist.
To sum up, protein is absolutely essential in the horse’s diet, but as with every aspect of feeding, balance is what counts. Both a shortfall and an excess can affect the horse’s health, fitness and wellbeing. Well-chosen protein sources, such as lucerne, oilseed cakes or peas, make it possible to build a balanced, healthy diet that supports muscle development, immunity and overall condition. A considered approach to feeding is the best way to keep a horse in excellent shape all year round. It is worth looking at its diet regularly and making changes based on its needs! 🐴💪