8/ APRIL 2023 THE RIDER Protein Requirements in the Equine Diet


able to understand the exact dietary re- quirements for individual amino acids. Now that we have established a


basic understanding of protein in the equine diet, let’s discuss which horses have a higher requirement for protein in their diet. A horse’s requirement for protein


depends on their physiological state as well as workload. Typically, horses do not have high protein requirements. In fact, most of the time their protein re- quirement can be met with quality for- age as long as the protein levels in the forage are adequate. That being said, occasionally, protein in the forage will not be adequate and an additional source must be added to the nutrition program – again this highlights the im- portance of a hay analysis. Growing horses, pregnant mares,


An Equine Nutrition Blog by Madeline Boast,


MSc. Equine Nutrition Protein is one of 6 nutrient classes


that horses have a requirement for. It is a major component of body tissues. Along with being a core component of tissues, proteins are also heavily in- volved in enzymes, hormones, and anti- bodies. Proteins are long chains of amino


acids, there are 21 amino acids that join in a multitude of combinations to form proteins. In equine nutrition, we divide the amino acids into essential and non- essential. The essential amino acids are those that the horse cannot produce and therefore must be supplied in the diet. They include: arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Unfortunately, the individual requirements for each amino acid have not been elucidated for horses except for lysine. More research is required to be


lactating mares, and horses under a moderate to heavy exercise regime will probably need additional protein. Mares in late gestation and those in the


first three months of lactation have the highest requirements. Best practice for these horses would be to first have them on a protein-rich forage such as legume- based hay, then add additional protein as needed. Although this sounds simple, there


is one more factor to consider. Not only do you need to ensure your horse has ad- equate protein in their diet, but it must also be high quality. Protein quality has to do with the


amino acid composition of that ingredi- ent as well as the digestibility. High quality protein provides essential amino acids in the correct proportions, whereas lower quality protein may be inadequate at providing essential amino acids or have poor digestibility. Therefore, when curating a diet for a horse that has in- creased protein requirements ensuring you are adding a good quality protein can make a significant difference in their nutritional well-being. When comparing feedstuffs based on protein quality a general rule is that


legume hay has a better protein profile than grass hay or pasture. Additionally, many cereal grains (barley, corn, oats) are considered to have low quality pro- tein. Typically, soybean meal is the go- to high quality protein source for horses as it provides a high percentage of ly- sine.


When evaluating your horse’s diet


for protein a hay analysis should AL- WAYS be done. This way a nutrition program can be built around the forage. After the hay analysis, if a nutritionist determines your horse needs an addi- tional source of protein added they will either recommend a single ingredient such as soybean meal or add a balanced complete feed. When shopping for a complete feed it pays off to do your re- search not only on protein content but also on protein quality!! When supple- menting protein, it is important to know the level to which to supplement as there are complications both with protein de- ficiency and with excess protein. Research suggests that protein de-


ficiency in the horse is less common when compared to the excess protein being provided. However, there are still negative health consequences associ- ated. Symptoms of protein deficiency in mature horses are muscle loss, weight loss, inadequate feed intake, and poor growth of hooves and hair. In addition to the previously listed symptoms, preg- nant mares may experience fetal loss as well as poor milk production if they are deficient in protein. In young horses, a decrease in growth is seen when protein is lacking in the diet. If you have a nu- tritionist complete a hay analysis, they will be able to determine if an additional protein source should be added to the diet.


When a horse is supplied with ex-


cess dietary protein that protein will be broken down and excreted from the body as urea in the urine. When there is additional urea to be excreted, the horse may experience an increase in water loss. When more water is lost, the water


intake requirement of that horse will in- crease. This could be problematic for horses under intense exercise who may already struggle with hydration. Research has shown that when


high protein diets are given to exercising horses it interferes with the acid-base balance in their body. Additionally, when horses urinate more and have a higher urea content in the urine it nega- tively impacts the air quality in the barn and can lead to respiratory problems down the road. A study using Arabian horses under


training has suggested that improving protein quality but decreasing protein quantity in the diet is a good option. This way you can ensure a working horse is not deficient in important amino acids such as lysine but avoid the undesired effects of greatly oversupplying protein. Another problematic consequence


of oversupplying protein is that the in- creased urea can lead to earlier fatigue during exercise. Another concern related to exercise is heat. When a horse is using protein for energy, they produce more body heat which increases sweating and therefore increases the risk of dehydra- tion in working horses. A final area that is important to


highlight is the environmental impact of providing excess protein in livestock nu- trition. Unfortunately, the equine sector does not have the same published pa- rameters on nitrogen and urea excretion as other livestock sectors, but it is well documented that when too much protein is fed, there is an increase in nitrogen re- leased in the urine. This negatively im- pacts both air quality and groundwater. Plus, protein shouldn’t be wasted! It is an expensive feed ingredient. To conclude, all of this highlights


the need for precision in ration forma- tion. Stop guessing with your horse’s nutrition! Have a hay analysis done and get an equine nutritionist to balance the diet to your forage analysis. If you have any questions, please reach out to Madeline at balancedbaynu-


trition@gmail.com


By: Madeline Boast, MSc. Equine Nu- trition About the author: Madeline Boast


completed her master’s in Equine Nutri- tion at the University of Guelph and started an independent nutrition com- pany known as Balanced Bay. She has worked with a variety of equids – from miniature ponies to competing thor- oughbreds. Through Balanced Bay she designs customized balanced nutrition plans that prioritize equine well-being. This includes diets for optimal perform- ance as well as solving complex nutri- tional issues and everything in between. For additional


information see www.balancedbay.ca


References: Graham-Thiers, P. M., Kronfeld, D. S., Kline, K. A., Sklan, D. J., & Harris, P. A. (2003). Dietary protein and fat effects on protein status in Arabian horses dur- ing interval training and repeated sprints. Journal of Equine Veterinary Science, 23(12), 554-559. Loos, C. M., McLeod, K. R., Stratton, S. C., van Doorn, D. A., Kalmar, I. D., Van- zant, E. S., & Urschel, K. L. (2020). Pathways regulating equine skeletal muscle protein synthesis respond in a dose-dependent manner to graded levels of protein intake. Journal of Animal Sci- ence, 98(9), skaa268. National Research Council. 2007. Nutri- ent Requirements of Horses: Sixth Re- vised Edition. Washington, DC: The National


Academies Press.


https://doi.org/10.17226/11653. Tanner, S. L., Wagner, A. L., Digianan- tonio, R. N., Harris, P. A., Sylvester, J. T., & Urschel, K. L. (2014). Dietary crude protein intake influences rates of whole-body protein synthesis in wean- ling horses. The Veterinary Journal, 202(2), 236-243.


Beyond the Wither Tracing A Saddle-Fitting Series by Holly Barnett, REMT, CSF


Beyond The Wither Tracing – Honour Thy Horse’s Wither


dle may cause damage… the withers are the most sen- sitive and most afflicted. The moment you bring out your horse, their withers are telling a story. Three main insults to this area are tree point length, tree width and tree (pommel) shape. Tree Point Length


Of all the areas a sad-


causes brutal pain and atro- phy when incorrect yet widely goes unnoticed. The


sole purpose of the tree point is to keep the pommel off the withers — to do this the tree point must match the height of the dorsal processes of the wither bones. Short tree points on tall withers are just floating — without a base they’re unable to support the pom- mel of the saddle. This places extreme pressure on the sides of the withers and under stirrup bar as the


also far too common, espe- cially ones that are too wide.


forces are inappropriately redistributed. Tree Width issues are


Too wide of a saddle means no base of support, once again causing the withers to get nailed by extreme con- stant pressure. Just because


your saddle clears the top of the withers doesn’t mean you’ll have adequate side wither clearance - which is inarguably critical for cor-


we’ll take a closer look at each of these factors. For the love of your horses’ withers, ensure your saddle is pro-


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both shape and length in this context. Typical pommel shapes include ‘A’ shape, ‘U’ shape and Hoop shape. Hoop shapes are for your tabletops – low and wide. ‘A’ shape is for the narrow high A-frame horses and U shapes are a common wither friendly style that can ac- commodate a variety of breeds including the thicker warmblood types. As dis- cussed in previous articles, it’s critical that the length of the pommel matches the length of the wither from behind the scapula to where it forms into the back. In the coming months


rect fit. Tree Shape refers to


tecting and not assaulting them!


Holly Barnett is profes- sional fitter and equine ther- apist for over 20 years. She’s worked with horses of all breeds and riders of all levels and disciplines throughout North America. Founder of August Equine, located in Campbellville ON, Holly now focuses on high level consulting, edu- cation and advocacy and is the creator of Saddle As- sessment 4 Equine Body- workers (SA4EB) Holly works with a small team of saddle-fitters


clients across Canada. For upcoming clinics and edu- cational events see www.au- gustequine.com.


servicing


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