How has horses' feed changed? Thoroughbred Nutrition Past & Present

Feeding practices for racehorses have changed as nutritional research advances and food is no longer just fuel but a tool for enhancing performance and providing that winning edge.  Whilst feeding is dominantly considered the content of the feed bucket, which by weight forms the largest part of the horse’s diet, changes in forage quality have also played a role in the changing face of thoroughbred nutrition. The content of the feed bucket, which is becoming increasingly elaborate with a multitude of supplements to consider, the forages—both long and short chop and even the bedding chosen—all play a part in what is ‘the feed program’. Comparing feed ingredients of the past against the present provides some interesting insights as to how the industry has changed and will continue to change.      Comparing key profiles of the past and present   The base of any diet is forage, being the most fundamental need of the horse alongside water. Forage quality and form has changed over the years particularly since haylage entered the market and growers began to focus specifically on equine. The traditional diet of hay and oats, perhaps combined with mash as needed, provided a significantly different dietary intake to that now seen for horses fed a high-grade haylage and fortified complete feed.  Traditional Diet  7kg Oats  1kg Mash – comprised of bran, barley, linseed and epsom salt  0.5kg Chaff  Hay 6% protein consumed at 1% of bodyweight       Modern Diet – medium-grade haylage  8kg Generic Racing Mix  0.5kg Alfalfa Chaff  60ml Linseed Oil  60g Salt  Haylage 10% protein consumed at 1% of bodyweight       Modern Diet – high-grade haylage  8kg Generic Racing Mix  0.5kg Alfalfa Chaff  60ml Linseed Oil  60g Salt  Haylage 13% protein consumed at 1% of bodyweight          The traditional example diet of straights with bran and hay easily met and exceed the required amount of protein providing 138% of requirement. When looking at the diet as a whole, the total protein content of the diet inclusive of forage equates to 9.7%. In comparison the modern feeding example using a high-grade haylage produces a total diet protein content equivalent to 13.5%. The additional protein whilst beneficial to development, muscle recovery and immune support can become excessive. High intakes of protein against actual need have been noted to affect acid base balance of the blood, effectively lowering blood pH (1). Modern feeds for racing typically contain 13-14% protein which complement forages of a basic to medium-grade protein content very well; however when using a high-grade forage, a lower protein feed may be of benefit. Many brands now provide feeds fortified with vitamins and minerals designed for racing but with a lower protein content.  Whilst the traditional straight-based feeding could easily meet energy and protein requirements, it had many short-falls relating to calcium and phosphorus balance, overall dietary mineral intake and vitamin intake. Modern feeds correct for imbalances and ensure consistent provision of a higher level of nutrition, helping to counterbalance any variation seen within forage. Whilst forage protein content has changed, the mineral profile and its natural variability has not.  Another point of difference against modern feeds is the starch content. In the example diet, the ‘bucket feed’ is 39% starch, a value that exceeds most modern racing feeds. Had cracked corn been added or a higher inclusion of boiled barley been present, this level would have increased further. Racing feeds today provided a wide range of starch levels ranging from 10% up to the mid-thirties, with feeds in the ‘middle range’ of 18-25% becoming increasingly popular. There are many advantages to balancing starch with other energy sources including gut health, temperament and reducing risk of tying-up.  The horse with a digestive anatomy designed for forages has limitations as to how much starch can be effectively processed in the small intestine, where it contributes directly to glucose levels. Undigested starch that moves into the hindgut is a key factor in acidosis and whilst still digested, the pathway is more complex and not as beneficial as when digested in the small intestine. Through regulating starch intake in feeds the body can operate more effectively, and energy provided through fibrous sources ensures adequate energy intake for the work required.      Feed ingredients for the modern racehorse   Moving from straights to completed bagged feeds has created a wider range of materials that are now easily fed. The inclusion of pellets within a muesli and cubes as a feed facilitate the use of various co-products. Having a wider range of feed materials to work with means a greater range of nutritional profiles are now available, with multiple combinations of protein, oils, starch and fibre. The old rule of thumb that as protein increases so would ‘energy’ namely in the form of starch no longer applies. A 10-11% protein feed is no longer exclusively a pony feed with a low value, but found in racing feeds used both in flat and national hunt.  Cereals are still the dominant inclusion in racing feeds with very few diets being cereal free. Oats as before remain the most popular grain as they offer the best protein, fibre and starch ratio of all the grains. Other materials, know as co-products, produced by other feed industries are now widely used along with grass or alfalfa meal. These alternatives to grain allow flexibility in designing both the energy and the protein profile of the feed.      Commonly Used Ingredients Typical Characteristics     When comparing cereals against the co-products, the difference in starch content is easily identified. Grass and alfalfa meal also offer a low-starch level whilst maintaining a good level of protein. Straw is less commonly used as the protein content and digestibility are lower than the other materials. Combining the groups in different ratios allows a wide range of starch levels to exist whilst still maintaining the appropriate level of protein. Whilst co-products are not whole foods, this does not mean their nutritional value is any less worthy of consideration or that they are not as valuable to the horse. Each brings its own benefits depending on what the diet is intended for. It is the combination of these materials that matters; the creation of a feed is somewhat of an art as much as it is a science.  Rice Bran  A co-product of rice milling whereby rough rice is dehulled to produce brown rice (a common human food) is then milled. Rice bran is produced during the milling process and is comprised of the pericarp (outer layer), the aleurone layer (inner layer), some endosperm and germ. It is valued for its naturally high-oil content, good protein content and moderate starch content relative to whole cereals.  Sugar Beet Pulp  The residue that remains after sugar has been extracted from sugar beet. It is not high in sugar as the name might imply, typically containing only 7% sugar. When molassed, the sugar content increases to around 20%. In the latter form, it is highly palatable and produces a glycemic response similar to that of oats, making it well suited for horses in training. It also influences hindgut fermentation having a natural prebiotic effect, making it ideal for racing where the environment and diet create challenges for the hindgut (2,3).  Soya Hulls  Derived from soya beans during processing. The hulls (outer shells) are removed and are highly fibrous with a crude fibre content of 35%—significantly higher than any grain but containing an equivalent amount of protein. Ideal for use when looking to increase fibre content and lower starch content of a feed.  Oatfeed  A co-product of oat milling made up dominantly of the oak hull (outer layer) with a high-fibre content. Beneficial when looking to provide fibre without elevating protein content.  Wheatfeed  Produced from wheat following extraction for flour. The profile of wheatfeed is based on the level of bran, germ and middlings. It provides a good level of protein, somewhat higher than whole grains and has a moderate starch content with only a low level of fibre compared to soya hulls or sugar beet pulp.     Wheat Grain Structure    http://www.nabim.org.uk/wheat-structure     Nutritionally Improved Straw (NIS)  Straw is highly fibrous and poorly digested. To improve digestion straw can be treated with an alkali, sodium hydroxide, at which point it becomes NIS. Less commonly used in thoroughbred feeds and primarily included for fibre content.     Grass Meal & Alfalfa Meal  Dried grass (grass meal) is produced from herbage that may contain a blend of grass, clover, alfalfa and sainfoin. The protein value depends upon plant maturity when harvested, but will be a minimum of 13% protein and typically 16% protein. Alfalfa meal, whilst commonly thought of as a forage in the same manner as hay, is by family a legume—the same as peas and beans. Alfalfa is often valued for its protein and mineral content, in particular its calcium level.     All ingredients used in a feed are listed in the composition section of the feed label. Their order of inclusion on the label relates to the weight of each material, the largest inclusion by weight being the first and then so on. Checking the feed composition section informs you as to what materials have been blended to create your feed. The composition of mixes and cubes for the same category of horse are often different as the variety of materials that can be made into a cube is much greater than those that can be used in a mix.      Feed Additions   In addition to the raw materials, many feeds now contain additional supplements or use alternative sources of vitamins or minerals based on research into their availability to the horse. This is the area of nutrition that continually progresses as such additions can impact performance. The majority of feeds on the market now deliver more than just protein, carbohydrate, fats, vitamins and minerals. The most commonly used additions include probiotics, prebiotics, maerl, plant-based antioxidants, vitamin C and natural forms of vitamin E.  Probiotics & Prebiotics  Live yeast culture, a form of probiotic is widely used to improve digestibility of the diet, increasing digestion of fibrous fractions, protein and minerals (4). In addition the prebiotic FOS, a short-chain fructooligosaccharide is sometimes included to promote the growth of beneficial gut bacteria such as  Bifidobacteria . Supporting beneficial bacteria can increase VFA (volatile fatty acid) production (5). These fatty acids are converted and used for energy. By maintaining a healthy hindgut profile, it is possible to maximise digestion and nutrient uptake.  Maerl  Also known as acidbuff or  lithothamnium,  maerl is a calcareous marine algae with a honeycomb-like structure that is effective in buffering acid in various parts of the digestive tract. It is naturally rich in minerals, most notably calcium and is more available to the horse than calcium carbonate (limestone). Its increased availability is also noted when fed in the presence of omeprazole, a commonly used medication that reduces calcium uptake (6). Its use in racing feeds and supplements is becoming more common, partly for its effect on regulation of acidity and its improved availability as a calcium source, but also for its role in bone development. Studies from Kentucky Equine Research have evidenced an improved bone density and thickness when using calcareous marine algae in the diet of thoroughbreds (7).  Plant-Based Antioxidants  There is an increasing interest in use of plant-based antioxidants to support the more commonly known antioxidants vitamin E and vitamin C. The blend of plants work synergistically, making them effective at low doses. Studies have evidenced a positive effect of such blends on plasma vitamin E, vitamin C and total antioxidant capacity (8).  Vitamin C  Whilst the horse can produce vitamin C from glucose and therefore it is not strictly required to be provided in the diet, the inclusion of vitamin C may have benefits. Vitamin C is an antioxidant and has a role in collagen development. Its use in feeds is part of a cocktail of antioxidants which is reflected by the inclusion rate. Some evidence exists for use of much higher doses of vitamin C for horses with respiratory issues or aged horses with compromised immune systems. A high dose for these specific situations, and for horses following surgery or with wounds to heal, is then advisable. As long-term high levels of intake are not well documented and such inclusions may impact on the horse’s ability to naturally synthesise vitamin C, its use should be moderated at high intakes to times of specific need only.     Vitamin E  Vitamin E is found in feeds in two forms within feed, as synthetic and natural. Also described as all-racemic (synthetic) and RRR (natural). The natural form is the most abundant type found within plants and is considered the most active form. Studies into horses at rest and when exercised have shown the natural form to be more effective at elevating plasma vitamin E status (9). Supplementing with vitamin E has many noted benefits for performance and is particularly relevant for horses with ERS. As with all nutrients, an excessive intake can be detrimental and should be carefully considered.      Summary   Modern feeds offer a wide range of nutrient profiles allowing more flexibility of feeding through use of a greater range feed materials, including co-products. Understanding the feed profile inclusive of starch content is important when selecting feeds best suited to the yard. Supplementation level within feed of antioxidants and additional benefits such as prebiotics has created feeds that deliver much more than traditional nutrition. When reviewing a feed, all factors including additional nutritional features should be considered. Nutrition is now a powerful tool when looking to enhance performance.      References  Graham-Thiers,P.M.,Kronfeld,D.S.(2005) Dietary Protein Influences Acid-Base Balance in Sedentary Horses.  Journal of Equine Veterinary Science  (2005) pp 434-438  2. Gebbink, GAR., Sutton, AL., Richert, BT., Patterson JA., Nielsen, J., Kelly, DT., Verstegen, MWA., Williams, BA., Bosch, M., Cobb, M., Kendall, D.C., DeCamp, S., Bowers K (1999) Effects of Addition of Fructooligosaccharide (FOS) and Sugar Beet Pulp to Weanling Pig Diets on Performance, Microflora and Intestinal Health.  Department of Animal Sciences, Purdue University, and Wageningen Institute of Animal Sciences, Wageningen Agricultural University, The Netherlands   3. Al-Tamimi, M.A.H.M., Palframan, R.J., Cooper, J.M., Gibson, G.R., Rastall, R.A (2006). In vitro fermentation of sugar beet arabinan and arabinooligosaccharides by the human gut microflora.  Journal of Applied Microbiology  100 (2006) pp 407–414     4.Glade,M.J. (2011). Dietary yeast culture supplementation of mares during late gestation and early lactation. Effects on dietary nutrient digestibilities and fecal nitrogen partitioning.  Journal of Equine Veterinary Science  11 (1991) pp 10-16     5.Berg,E.L.,Fu.J.H.,Porter,J.H.,Kerley,M.S.(2005) Fructooligosaccharide supplementation in the yearling horse: Effects on fecal pH, microbial content, and volatile fatty acid concentrations.  Journal of Animal Science  83 (2005) pp 1549–1553  6. Pagan,JD. Petroski,LA., Mann,AC., Hauss,AA., Huntingdon,PJ. (2018) Effect of Omeprazole and Calcium Sources on Calcium Digestibility in Thoroughbred Horses.  Proceedings of the Australasian Equine Science Symposium.   7. Pagan, JD., Swanhall, A., Ford, E., Mulvey, E., & Huntington, PJ. (2018) Mineral and Vitamin Supplementation Including Marine Derived Calcium Increases Bone Density in Thoroughbreds.  Proceedings of the Australasian Equine Science Symposium.   8.Lowe, J.A., Lucas, D., Paganga, G., Observations on the antioxidant status of horses as influenced by supplementary dietary antioxidants.  9. Pagan, JD.(2006) Tocopherol form affects vitamin E.  Feedstuffs  78 (2006)

By Catherine Rudenko

Feeding practices for racehorses have changed as nutritional research advances and food is no longer just fuel but a tool for enhancing performance and providing that winning edge. 

Whilst feeding is dominantly considered the content of the feed bucket, which by weight forms the largest part of the horse’s diet, changes in forage quality have also played a role in the changing face of thoroughbred nutrition. The content of the feed bucket, which is becoming increasingly elaborate with a multitude of supplements to consider, the forages—both long and short chop and even the bedding chosen—all play a part in what is ‘the feed program’. Comparing feed ingredients of the past against the present provides some interesting insights as to how the industry has changed and will continue to change.

Comparing key profiles of the past and present 

The base of any diet is forage, being the most fundamental need of the horse alongside water. Forage quality and form has changed over the years particularly since haylage entered the market and growers began to focus specifically on equine. The traditional diet of hay and oats, perhaps combined with mash as needed, provided a significantly different dietary intake to that now seen for horses fed a high-grade haylage and fortified complete feed. 

Traditional Diet

  • 7kg Oats

  • 1kg Mash – comprised of bran, barley, linseed and epsom salt

  • 0.5kg Chaff

  • Hay 6% protein consumed at 1% of bodyweight

May article diet 1.png

Modern Diet – medium-grade haylage

  • 8kg Generic Racing Mix 

  • 0.5kg Alfalfa Chaff

  • 60ml Linseed Oil

  • 60g Salt

  • Haylage 10% protein consumed at 1% of bodyweight

May article diet 2.png

Modern Diet – high-grade haylage

  • 8kg Generic Racing Mix 

  • 0.5kg Alfalfa Chaff

  • 60ml Linseed Oil

  • 60g Salt

  • Haylage 13% protein consumed at 1% of bodyweight

May article diet 3.png

The traditional example diet of straights with bran and hay easily met and exceed the required amount of protein providing 138% of requirement. When looking at the diet as a whole, the total protein content of the diet inclusive of forage equates to 9.7%. In comparison the modern feeding example using a high-grade haylage produces a total diet protein content equivalent to 13.5%. The additional protein whilst beneficial to development, muscle recovery and immune support can become excessive. High intakes of protein against actual need have been noted to affect acid base balance of the blood, effectively lowering blood pH (1). Modern feeds for racing typically contain 13-14% protein which complement forages of a basic to medium-grade protein content very well; however when using a high-grade forage, a lower protein feed may be of benefit. Many brands now provide feeds fortified with vitamins and minerals designed for racing but with a lower protein content. 

Whilst the traditional straight-based feeding could easily meet energy and protein requirements, it had many short-falls relating to calcium and phosphorus balance, overall dietary mineral intake and vitamin intake. Modern feeds correct for imbalances and ensure consistent provision of a higher level of nutrition, helping to counterbalance any variation seen within forage. Whilst forage protein content has changed, the mineral profile and its natural variability has not. 

Another point of difference against modern feeds is the starch content. In the example diet, the ‘bucket feed’ is 39% starch, a value that exceeds most modern racing feeds. Had cracked corn been added or a higher inclusion of boiled barley been present, this level would have increased further. Racing feeds today provided a wide range of starch levels ranging from 10% up to the mid-thirties, with feeds in the ‘middle range’ of 18-25% becoming increasingly popular. There are many advantages to balancing starch with other energy sources including gut health, temperament and reducing risk of tying-up. 

The horse with a digestive anatomy designed for forages has limitations as to how much starch can be effectively processed in the small intestine, where it contributes directly to glucose levels. Undigested starch that moves into the hindgut is a key factor in acidosis and whilst still digested, the pathway is more complex and not as beneficial as when digested in the small intestine. Through regulating starch intake in feeds the body can operate more effectively, and energy provided through fibrous sources ensures adequate energy intake for the work required. 

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