Engines are usually measured and compared on the basis of their ‘horse-power’. Comparing the competition horse to a high-performance car, the speed, power and stamina are not determined by the size of the fuel tank. They are determined by the size of the engine! A smaller engine = less power and endurance. In the horse, the engine is the muscles.
Image: Digital Library @ Villanova University, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons, available here.
The size and number of muscle fibres that a horse can build depends on the availability of various protein – not energy, oats or grain… they are fuel and they don’t build muscle, speed, strength or stamina. It is the muscles that provide the horse-power. Certainly they need fuelling, but more fuel doesn’t make more muscle. Think about your home – the electricity provides the energy and fuel, but it doesn’t build a house – for that we need a strong foundation, frame, bricks and mortar.
A horse’s frame, foundation and body are built from different proteins (plus vitamins and minerals) – not energy.
Each tissue in the body has its own specific protein needs. The blood is like a conveyor belt or transport system, bringing to the tissues the nutrients from the feed. The tissues select which ones they need to create, repair and build their cells and structure. If the blood runs out of the proteins a particular tissue needs, the production of new cells stops. Similar to making a cake, you need flour, eggs and cocoa etc to make a chocolate cake. If you run out of cocoa, chocolate cake production stops. You might be able to make other cakes with the left-over ingredients, or you might have to throw them out. Either way, chocolate cake production ceases. In horses, unusable protein is converted to fat.
Proteins are made of chains of different amino acids. In nature there are roughly 500 amino acids, but just 20 amino acids make up the proteins found in the body. Of these, the horse’s liver can make 10 from the raw ingredients in the diet. The other 10 must come preformed in the feed. These are called ‘essential amino acids’. The horse uses lysine, methionine, threonine, histidine, leucine and arginine in almost every tissue.
Just as a plank that is not in the correct amount to form the sides of a complete barrel will limit the contents of the barrel, a deficiency of any single essential amino acid one will place a limit on cell and tissue creation, building and repair.
Image to left and on feature tile, from Fickr.
Every protein in feedstuffs has its own combination of amino acids – soybeans and lucerne are high in essential amino acids, but oats and grassy hays are low. This is what makes soy and lucerne good protein sources for a horse.
How much protein does a horse need?
It depends on age, breed, workload and bodyweight – but they all need a number of grams a day – not a percent! For example if a horse is fed each day 1kg of a 30% protein feed, it gets 300g of protein a day. If it is fed 2kg each day of a 15% protein feed it still gets 300g of protein. So % protein is not a basis on which to compare feeds. And if the protein in a feed does not have the correct essential amino acids, it might only be 50% useable protein. This is why % protein tells you nothing about how well your diet is meeting the amount of protein and the essential amino acid requirements of your horse.
DISCLAIMER All content provided in this article is for general use and information only and does not constitute advice or a veterinary opinion. It is not intended as specific medical advice or opinion and should not be relied on in place of consultation with your veterinarian.
More information on equine nutrition is available at www.jenquine.com
Meet the author and PCA’s resident equine nutritionist
Dr Jennifer Helen Stewart
BVSc BSc PhD Dip BEP MRCVS
Equine Veterinarian and Consultant Nutritionist – CEO Jenquine
Dr Jennifer Stewart is an equine veterinarian with over thirty five years’ experience. She is also a consultant nutritionist and has formulated feeds, custom mixes and supplements for leading international horse feed manufacturers in Australia, India, Ireland, Japan, New Zealand, Philippines, South Africa, Thailand, Turkey and the UAE. Dr Stewart is passionate about equine nutrition and its role in the management, treatment and prevention of many equine diseases. She is committed to bringing ‘science to the feed bin’.
Dr Stewart graduated BSc (vet) and BVSc at the University of Sydney. Her research thesis was “Resistance of Equine Strongyles to Benzimidazole Anthelmintics” and her PhD “Studies on Heart and Lung Function in Foals”. She worked at the Universities of North Carolina, Michigan and Florida USA in equine medicine, antibiotics and exercise physiology. Following this was a time spent in Newmarket and Cambridge England, in stud and race track research and practice, before establishing an exclusively equine practice on the Central Coast of NSW Australia. She has been an official veterinarian for the Australian Jockey Club for over 20 years, was one of the team of equine veterinarians for the Sydney 2000 Olympic Games and consultant nutritionist for Mitavite for 10 years.
Dr Stewart has spent over twenty five years working on collaborative research projects into gastrointestinal and exercise physiology with major Universities; lecturing and supervising university and TAFE students; consulting to veterinary practices, trainers, pony clubs, owners, equestrian centres and studs; speaking at seminars in Australia, Middle East, South Africa, Philippines, SE Asia, Hong Kong, Japan, Turkey, India and New Zealand, and writing regularly for equine industry magazines. This experience in research, equine medicine and veterinary practice has given Dr Stewart a deep understanding of the complexities of equine health and performance; growth and development of young horses, and feeding practices for the management and prevention of diseases.
Watch Dr Stewart talk about her first love of horses and why she chose to become a vet in this short clip. Pony Club Australia is grateful for Dr Stewart preparing this laminitis article for our Horse Resource page. Please browse her other articles, blog and resources at Jenquine.