Protein Quality and Quantity

Protein Quality and Quantity

Protein makes up an important part of a horse’s diet. It is a nutrient as well as a building block for all living organisms.  Protein contains amino acids that the body needs for cell building and other metabolic processes. In the equine body, tissues are made up of cells. All these cells – for example in muscles, organs, the nervous system, bones, skin but also  blood and immune cells – contain protein. In this article, read about the importance of feeding your horse high-quality protein.

Whatever sport you and your horse are involved in, muscles are important. Strong muscles support the equine skeleton. Well-developed muscles provide better support to the spinal column and joints. Skeletal muscle consists of 75% protein, which is why it’s important that the horse’s diet contains sufficient protein. However, not all protein gives the same result. High-quality proteins provide the right building blocks – amino acids – in the correct ratio and quantity. The quantity and quality of protein needed for optimum muscle building in horses was not well known until recently. Because high-quality protein sources are expensive and the total protein content in equine diets often exceeds the daily needs of the horse, more research was needed looking into the quality and quantity of protein in equine rations in relation to maximum stimulation of protein synthesis in the muscles.

Scientific research

Dr. Caroline Loos, postdoctoral scientist at the University of Kentucky (USA), does research on optimising protein nutrition in relation to muscle development. She recently completed 2 studies examining the impact of protein quantity and quality on the activation of the muscle mTOR signalling pathway in mature horses. Activation of the mTOR pathway is an essential trigger for the protein synthesis process and thus for building muscle mass. First, Dr. Loos looked at the effect of graded levels of high-quality protein intake on the activation of the muscle mTOR signalling pathway1. She then compared two different protein sources to determine which protein type most strongly activates muscle protein synthesis2. She also examined how long the mTOR pathway remained activated after a high-protein meal2. Finally, she examined the difference, if any, between the activation of muscle protein synthesis in healthy horses and in horses with insulin dysregulation2.

Protein quantity – maximum response

The objective of the first research project by Dr Loos was to determine how much protein a horse should consume for the maximum activation response of muscle protein synthesis. She conducted the study in adult horses that were not in work (on maintenance diets). A high-quality protein source was also specifically chosen to provide a strong stimulus (Cavalor VitAmino, containing protein from soy, alfalfa, and potato protein). Muscle protein synthesis occurs through the stringing together of different amino acids to form a long chain to create a new protein. The mTOR pathway regulates and directs this process. Insulin, exercise, and in particular the presence of essential amino acids from high-quality protein activate this pathway. Once activated, mTOR sends a signal to initiate protein synthesis in muscle cells. The result is muscle building. The study showed that consumption of about 140 g of high-quality protein (0.25 g crude protein/kg body weight) per meal maximised stimulation of the protein synthesis pathway in an adult horse on a maintenance diet. Interestingly, the study also showed that consumption of more than this amount of protein had no additional effect on the activation of the mTOR pathway.

Protein quality 

In addition to insight into the optimum quantity, the quality of protein is also a key determinant for maximum muscle building. A protein’s “quality” is determined by (1) the amino acid profile, and (2) the digestibility of the protein source. The better the protein is digested, the more amino acids can be absorbed and subsequently used for muscle building. The amino acid profile determines which specific amino acids are supplied by the protein. For optimal muscle building, it is best to choose a protein source that provides muscle protein-specific amino acids. Here the essential amino acids are particularly important. Some essential amino acids, such as leucine, are not only building blocks but also act as signalling agents. For example, leucine strongly activates the mTOR pathway. Protein sources rich in leucine therefore ensure better muscle growth.

The follow-up study compared the effect of two different protein sources on the activation of the muscle mTOR protein synthesis pathway. One was a protein source from forage, an alfalfa pellet, and the other was a high-quality protein balancer pellet (Cavalor VitAmino). The latter contains a mix of soy, alfalfa, and potato protein. This study also used adult horses on maintenance diets and both protein sources were fed in the same amount of crude protein per kg of body weight. Both experimental pellets were also formulated to contain an identical amount of starch, sugars, and any other ingredients so that only the protein source differed between the treatments. The results showed that the consumption of Cavalor VitAmino caused a stronger increase in essential amino acid levels in the blood and subsequent stronger activation of the mTOR pathway compared to alfalfa. The higher-quality protein source therefore provided better trigger for muscle protein synthesis than the lower-quality protein source. The study also showed that maximum activation of the mTOR pathway for both protein sources occurred approximately 90 minutes after the meal and then slowly decreased over a period of 5 hours. Finally, the study showed that insulin dysregulation had no adverse effect on the activation of the mTOR pathway in the muscles after a high-protein meal.

Practical conclusions from science

From the above studies, we conclude that quality, not quantity, is the important muscle-building factor when it comes to protein feeding for horses. With a higherquality protein source, less protein needs to be consumed to obtain a maximum response in activation of the muscle protein synthesis pathways. This could possibly reduce the amount of protein in the diets of horses. Excess protein in the ration is associated with potential negative health effects, causes environmental pollution and is costly for feed producers and ultimately horse owners. Furthermore, research now shows that feeding excess provides no additional benefit in most cases.
So, for optimum results and maintaining your horse in good health, increase the quality of your protein sources rather than the quantity. Finally, a high-quality protein source can also be useful for muscle maintenance in horses with decreased insulin sensitivity.

Cavalor VitAmino 

Cavalor VitAmino contains easily-digestible, high-quality protein sources with  a unique  amino acid profile that specifically targets muscle mass development developing . Cavalor VitAmino contains highly digestible protein sources from soy, alfalfa, and potato protein, which contain all the essential amino acids in the right proportions for strong muscles and optimum recovery. Cavalor VitAmino contains an amino acid profile that is very similar to that of equine muscle protein. Important essential amino acids such as lysine, methionine, and leucine are crucial building blocks and ensure extra activation of muscle protein synthesis.

For more information on our scientific studies:
  1. Loos CMM, McLeod KR, Stratton SC, van Doorn DA, Kalmar ID, Vanzant ES, Urschel KL. (2020) Pathways regulating equine skeletal muscle protein synthesis respond in a dose-dependent manner to graded levels of protein intake. Journal of Animal Science. Vol. 98 Issue 9, skaa268.
  2. Loos CMM, McLeod KR, Vanzant ES, Stratton SA, Bohannan AD, Coleman RJ, van Doorn DA and Urschel KL (2022) Differential effect of two dietary protein sources on time course response of muscle anabolic signaling pathways in normal and insulin dysregulated horses. Frontiers in Veterinary Science. 9:896220. doi: 10.3389/fvets.2022.896220

Useful Products