Fuelling the racehorse - time for a paradigm shift!

Article by Dr Katie Williams

What does it take for received wisdom to be overturned and new approaches adopted? Revelatory research findings? Social demand for change? Both could actually result in a change to the way racehorses are fed today as welfare and sustainability in equestrian sport are increasingly scrutinized and researchers find ways to feed and manage horses more sympathetically and sustainably. 

Can we feed a racehorse more sympathetically - evolutionary considerations 

The horse is a herbivore and as soon as we prevent them eating as they have evolved to do, there are repercussions for their health and well-being. The increasing frequency with which ulcers are being diagnosed may account for why the recommendations for the minimal amount of forage a horse requires has increased in recent years. Rendle et al. (2020) cite 1.5% of bodyweight on a dry matter basis which is the level most equine nutritionists would advocate for the long-term health of the horse. 

The glandular region of the horse’s stomach contains glands that secrete hydrochloric acid, pepsin, bicarbonate and mucus. The stomach secretes acid continuously; as the horse is a trickle feeder it has evolved to do so continuously and it is important to note that this process continues even when the horse isn’t eating. This is why periods of more than 6 hours without access to forage are a risk factor for ulcers. The volume of secretion has been shown to be around 1.5l of gastric juice per hour although this does vary at different times during the day. Consuming too little fiber and eating materials that are high in starch, means acidity levels increase in the stomach. This not only increases the risk of ulcers but also changes the environment in the stomach sufficiently to impact the microbes that live there. Microbial dysbiosis in the stomach is increasingly being linked to an increased risk of gastric disease, particularly in the glandular region which is now recognized as an inflammatory disease rather than an ulcerative one.   

There are other potential health issues to consider too. It has been shown in trials in mice for example, that a low fiber diet increases the permeability of the gut – a phenomenon known as leaky-gut syndrome. When fibre is fermented in the hind gut, one of the volatile fatty acids produced is butyrate and this is the energy used by the colonocytes (gut cells) themselves. Insufficient fiber and therefore butyrate, can compromise the health of the cells creating bigger gaps between them which allows contents of the gut that shouldn’t pass through, to do so. The racehorse is repeatedly exposed to new and different environments when travelling to different racecourses and encounters pathogens they might have no previous immunity to. Their reduced defensive barriers in the gut mean they are more vulnerable to these pathogens which can result in digestive upsets.  

So can more fiber be fed without compromising performance? 

Researchers at the Lab to Field research center in Dijon, France believe so.  In work funded by the French government and published in Frontiers in Physiology, they found that Standardbred horses in training fed a third of their total ration as alfalfa with just 7% oats, performed comparably with those fed 33% oats (the remainder of the diet was hay). The horses were monitored over an 8 week period rather than just in a one-off standardized exercise test (SET). The replacement of a significant proportion of oats with alfalfa had no detrimental effects on performance or muscle tone and in fact, altered energy metabolism in such a way as to potentially improve performance and recovery the authors suggest (Martin et al., 2023). Studies back in the early 2000s (Nadeua et al, 2000; Lybbert et al, 2007) showed that alfalfa was more beneficial for horses with ulcers compared to grass forages because it helps counter the increased acidity that occurs when feeding cereals. This latest study suggests that alfalfa can actually replace a significant proportion of the cereals as an energy source too. 

The prevalence of gastric ulcers means it is an issue that needs to be addressed especially when viewed in the context of equine welfare in sport. Two recent studies have again shown how alfalfa has a key role to play in this regard too. The Lab to Field research group demonstrated that clinical success with horses with EGGD was 47.7 times more likely in horses fed alfalfa pellets as part of their ration compared to those on concentrate only rations (Julliand et al., 2023). 

In addition, a study published in 2024 showed that a combination of alfalfa, sugar beet and cereal fiber fed alongside the existing ration, aided the reduction in recurrence of gastric ulcers when fed during the healing and post-medication periods. This is key for when ulcer medication is stopped and the recognized rebound increase in acid production can occur (Menzies-Gow and Shurlock, 2024). 

A key point from these studies is that the quality of fiber matters. Alfalfa and sugar beet both contain higher proportions of digestible fiber such as pectin and hemi-cellulose, rather than indigestible fibrous elements such as lignin. This means they aren’t sitting in the gut for so long but they are being digested and utilized as an energy source. If fed in chopped forms they help to increase the amount of chewing the horse does and more chew time might actually be a relatively simple step in the right direction from a welfare perspective. The pros and cons of turning out racehorses have been widely debated but for those where it isn’t (currently) practical, it is surely a positive action to at least provide the horse with high fiber materials to eat when stabled, especially when it isn’t having a negative impact on their performance.

Dispelling Myths - Facts about Fibre

How much sugar does sugar beet contain?

The pulp fed to horses is actually really low in sugar – less than 5% assuming no molasses has been added back in. This is because the sugar has been extracted for use in the human food industry and the fibrous pulp is used for animal feed. 

Why does alfalfa contain more calcium than grass forages? 

Alfalfa has really deep roots – about 3 to 4 meters – and the calcium at this depth in the soil is more available for absorption. This means that alfalfa plants can take up more calcium than grass – chopped alfalfa contains between 30 - 50% more calcium than grass forages. Early studies suggest that omeprazole is reducing calcium absorption in the horse as is seen in humans and in Swanhall et al’s (2018) study, they recommend using bio-available calcium sources in the diet to help counteract this effect. Plant based sources of calcium such as alfalfa are much easier for the horse to absorb than inorganic sources such as limestone flour. 

Why is alfalfa so low in starch?

Like other plants alfalfa makes sugar when photosynthesizing but it stores any surplus sugar as starch in its roots – the part that horses don’t eat! Grass plants tend to store sugar as fructan in leaves and the stem which is why they supply the horse with more sugar. 

What contribution can forage make to a racehorse’s requirements? 

Remember that grass-based forages contain sugar, both simple sugar (glucose, fructose etc) and as water soluble carbohydrates or storage sugars (fructan). 10kgs of hay can provide around 1kg of simple sugar and in the region of 2-2.5kgs of storage sugar. This supplies around 20% of the energy required by a 500kgs horse in intense training. Additionally, forage provides energy from the fiber it contains and so overall, including the contribution from sugar, 10kgs of hay would supply around 60-70% of the horse’s energy needs depending on the quality of the forage. 

Earlier cut forages tend to be more digestible and therefore supply more energy. These tend to be the wrapped forages in the UK and other wetter and colder European countries as there just aren’t long enough periods of dry weather to make good hay very often. Why is this significant? The way forages are conserved has changed over the years so now, a more accurate description of many forages previously defined as haylages, would be ‘wrapped hay’ as they are often very dry which has meant that little or no fermentation has occurred. This means the levels of acidity are no different to a normal hay which can be seen from the analysis results in table 1. Using lactic acid levels as a marker of acidity levels shows that most of the wrapped forages analyzed in the UK are too dry for fermentation to occur and so the level of acidity is no different to hay. 

Table 1 A comparison of different forages 

Concern about using a true haylage for horses with ulcers relates to the increased acidity from the fermentation that occurs. Clearly this doesn’t apply if the forage hasn’t fermented and so a wrapped hay may well be a really useful option for a horse with ulcers. They tend to be more palatable and softer than hay. It is important to know the level of acidity before making the decision to use a wrapped forage and having it analyzed is therefore advisable. 

So if the paradigm shift happens, what will a racehorse’s diet look like in years to come? 

The basis would be a good, early cut wrapped hay. The daily bucket feed would consist of 1-2kgs of oats with 1.5kgs of alfalfa pellets, 1.5kgs of chopped alfalfa and 0.5kgs of soaked sugar beet. The chopped alfalfa  contributes to the horse’s overall forage requirement so if the dry matter of the wrapped hay is around 75%, a 500kgs horse would need a minimum of 8kgs per day to supply 6kgs of additional fiber on a dry matter basis. 

Key takeaways 

  • ESGD risk factors are well established and include too little fiber and too much starch 

  • Feeding at least 1.5% of bodyweight on a dry matter basis is the minimum amount of forage required for long term gastric and digestive health

  • Wrapped hays that have not fermented and so are no more acidic than hay are also appropriate to use for horses with ulcers

  • EGGD is still not fully understood but increasingly it is acknowledged by researchers that stress is a key contributing factor

  • Studies have shown alfalfa to be beneficial as an alternative energy source compared to cereals for horses in training



References 

Julliand et al (2023) Effect of diet composition on glandular gastric disease in horses. Journal of Veterinary Internal Medicine

Lybbert et al (2007), Proceedings of Annual Convention of the AAEP, Orlando, Florida, 2007. 

Martin et al (2023) Effect of high-starch or high-fibre diets on the energy metabolism and physical performance of horses during an 8-week training period. Front. Physiol. 14:1213032. doi: 10.3389/fphys.2023.1213032

Menzies-Gow and Shurlock (2024) The effect of feeding a commercial feedstuff on equine gastric squamous disease. Journal of Equine Veterinary Science. 133. 

Muller and Uden (2007) Preference of horses for grass conserved as hay, haylage or silage. Animal Feed Science and Technology, 132, (1-2) 66-78

Nadeau et al (2000) Evaluation of diet as a cause of gastric ulcers in horses. American Journal of Veterinary Research. Jul;61(7):784-90.

Pratt et al, (2022) Assessment of agreement using the equine glandular gastric disease grading system in 84 cases. Veterinary Medicine Science, 8 (4) 1472-1477doi: 10.1002/vms3.807

Swanhall et al (2018) Mineral and Vitamin Supplementation Including Marine Derived Calcium Increases Bone Density in Thoroughbreds. Proceedings of the Australasian Equine Science Symposium

Trust Your Gut – the importance of nutrition for health, performance and longevity

Article by Dr. Richard McCormick, M.V.B., Dip. Eq.Sc., M.R.C.V.S. 


The science of equine nutrition is really quite simple – The horse is a flight animal and in the wild, needs to be able to escape from predators using a short burst of energy. Nutrition and subsequent ‘energy’ for survival is all provided by grass which has the required balance of vitamins, minerals, immune supportive nutrients and  fiber to maintain a healthy gut microbiota and keep the horse in adequate health for reproduction. Proper functioning of the gastro-intestinal tract (GIT)  in horses is dependent on a broad range of micro-organisms and more than half of the energy requirement for their survival comes from the microbial fermentation occurring in their enlarged caecum and colon (Chaucheyras-Durand et al 2022). The bacterial populations resident in the various compartments of the horses intestinal tract vary greatly (Costa et al 2015) and there is more DNA in the bacteria located in the gastro-intestinal tract  than there is in the entire body. Because of this, having a healthy gut flora is critical to having a healthy immune system.

In modern times, our demands of horses for performance for our pleasure rather than their survival has led to their need for increased energy that cannot be provided from grass alone. Because of this, the intricacies of diet (in particular the consumption of starch, fiber and fat) has come under scrutiny. Equine feed manufacturers have looked for additional sources of starch, a carbohydrate and a natural component of grass that is ‘essential  to provide energy, fiber and a sense of fullness’ (Seitz 2022). Today, most horses and rapidly growing foals are commonly fed diets with >50% of total ration by weight in the form of grain ‘concentrates’ and carbohydrates from oats, maize, soya, barley and wheat. These grain based feeds contain high concentrations of soluble, easily fermentable starches but can be deficient in certain minerals and vitamins so getting an optimally balanced feed ‘right’ is difficult.

Too much of a good thing  

With advances in scientific knowledge, we now know that when a horse is exposed to surplus starch, the hydrogen ion concentration of their gut increases promoting  the production and absorption of lactic acid, acetate and propionate through the activity of fermentation (Ralston 1994). The process is quick, with lactic acid entering the bloodstream within 3 hours of feeding and calcium subsequently being excreted in the urine.  In order to combat this nutrient loss, the horses’ hormone system triggers the release of parathyroid hormone into the bloodstream, activating the release of stored calcium (to maintain optimal blood levels) but unfortunately causing  bone demineralisation. Clinically, the horse experiences health consequences of varying degrees including digestive diseases (eg: gastric ulcers, diarrhea, colic or colitis), muscle dysfunction (eg: rhabdomyolysis (known as ‘tying up’), defective bone mineralization (expressed as increased incidence of stress fractures and developmental orthopedic diseases), systemic diseases (such as laminitis, equine metabolic syndrome and obesity (Chaucheyras-Durand et al 2022) as well as potential causes of fatigue.

The ideal equine diet 

There is little equine focused research available on the benefits of individual nutrients (due to limited numbers in trials and their subsequent evaluation) of grain ‘concentrates’. But we do know that ingredient availability and quality is regularly influenced by market pressures. 

The table (fig 1) below outlines the sugar, starch and fiber components of the various ingredients commonly found in horse feeds. The optimal grain for equine nutrition with its efficient energy source through lower starch content (relative to other grains) and its high level of soluble fiber (relative to other grains) are oats.

The healing power of omegas and short chain fatty acids 

While grass provides optimal equine nutrition in its own right, the ‘curing process’ when making hay depletes the valuable omegas 3 and 6 intrinsic in grass. These ‘healing’ nutrients naturally protect the lining of the gastro-intestinal tract by increasing mucous production and alleviating ‘auto digestion’ (via hydrochloric acid). For horses, bacterial fermentation in the hind gut also results in the production of Short Chain Fatty Acids (SCFAs), namely acetic, proprionic and butyric acids. These SCFAs ‘cross talk’ with the gut immune system providing local immunity in the gut as well as protection of the respiratory system, the brain and other tissues against disease. In human medicine, it has been repeatedly established that a dysfunctional gut microbiome is associated with respiratory problems. This is evidenced by the fact that when gut disorders such as Irritable Bowel Syndrome  (IBD) or Coeliac disease exist in humans, they are commonly associated with a higher incidence of respiratory infections and related asthmatic like conditions. Barragry (2024) explores the relationship (Fig 2) between gut microbiome and the immune system's ability to support health and combat disease in cattle. A scenario mirrored in the equine.

The stabled horse should be provided with SCFAs daily to support proper functioning gut microbiome. This critical dietary consideration should ideally be provided in the form of flaxseed which has the highest ratio of omegas 3 and 6 (in the ideal ratio 4:1) in the plant world and is most suitable for the equine herbivore.

The health benefits of flaxseed for both humans and equines has been recognized as early as 3,000 BC. Flaxseed was used for various medicinal purposes such as the treatment of gastric disorders, as a soothing balm for inflammation and as a laxative (Judd, 1995). Horsemen (who relied heavily on their equines) and trainers (who sought optimal performance from their charges through natural means) also used flaxseed as a way to supplement the diet with omega-3’s and fiber to produce high quality proteins. Now, thirteen centuries later, we have research to substantiate the knowledge of our ancestors. The renowned German researcher of ‘fats’ and pioneer in human nutrition, Dr. Joanna Budwig, as early as the 1950’s reported that “the absence of highly unsaturated fatty acids causes many vital functions to weaken". Dr. Budwig’s life’s work focused on the dietary ‘imbalance’ between omega-3 and omega-6 fatty acids in humans has been a cornerstone to the exploration of the role of inflammation and the development of many diseases of the coronary, respiratory, metabolic and immune system.

The small seed of the flax plant is also an excellent source of high-quality protein (exceeding that of soybeans and fish oils) and potassium (a mineral that’s important for cell and muscle function). But, the true power of flaxseed lies in three key components: 

Omega-3 essential fatty acids – Also known as "good" fats, omegas enhance the oxygen usage of cells and in combination with alpha-linolenic acid (ALA) are anti-inflammatory in their effect within the body.

Lignans – Flaxseed contains 750 - 800 times more lignans than other plant foods (McCann 2007, Yan 2014). Lignans are a group of compounds with antioxidant properties which also contain plant estrogen. Lignans are linked to a reduced risk of developing osteoporosis, heart disease and cancer.

Fiber - Flaxseed contains both the soluble and insoluble types of fiber essential for maintaining ‘gut’ health.

In equines, adding flaxseed to the diet has the immediate benefits of a shiny, healthy coat and fewer skin allergies. Consistent use of flaxseed has multiple long term benefits including strong hoof quality, improved joint health, reduced muscle soreness, faster healing of ulcers (Sonali et al 2008) and significantly impacts inflammation associated with chronic skin conditions (commonly known as ‘sweet itch’). In breeding stock, increased Omega-3 levels in mares’ milk leads to boosted immunity in foals with higher stallion fertility and improved conception rates in broodmares documented (Holmes, 2015).

How diet can influence performance 

It is easy to think that ‘providing more is better’ when it comes to using nutrition to support performance. But having excess levels of essential vitamins and minerals being processed by the horses’ sensitive gut has a direct impact on their behavior and willingness to perform. Today, we have greater ‘choice’ at the feed store with a broad range of commercial feeding offerings available including mixes, mashes and supplements but the discerning horse owner can be forgiven for being overwhelmed by the range of diet options for every ailment and stage of life.

In modern times, despite advances in nutrition offerings, we have seen a falloff in performance (Fig 3). During the late 1960s, the U.S. Jockey Club stats noted that racehorses averaged 12 starts per year – a far cry from today's horses racing in the U.S. where the average of 3 ‘starts’ was highlighted by leading US Trainers in 2020 (www.ownerview.com). Unfortunately, this is not just a U.S. based problem, but a phenomenon noted worldwide.

The first equine pelleted feed was formulated in the US by the Cistercian  monks in Gethsemani, Kentucky in 1957. Prior to this, all horses were fed ‘straights’ (primarily oats as their energy source and flaxseed as their protein source). My own understanding of the link between modern feeding practices and compromized performance since the 1960s has been curated off an understanding of “what was different” then, as well as a career of observations, clinical practice and scientific review. Fact is, the equine diet of the 1960s was lower in starch and high in fiber. It consisted of oats, minerals, and flaxseed as the “norm”. Hay was the preferred forage (Fig 4).

Today, soya (with one fifth of the omega 3 content of flaxseed) has practically replaced flaxseed as the protein source in equine nutrition. This small change has seen a significant drop in omega-3 and 6 (needed for prostaglandins) in the diet with consequential gastro-intestinal and joint issues. Other dietary changes include those recommended by the National Research Council (NRC) in 1978, who suggested doubling the recommended calcium levels for horses with a subsequent increase in levels of Osteochondrosis (OCD) and Osteopetrosis in the equine population (Krook and Maylin, 1989). Additional moisture in the diet too has led to excess mould formation in convenience feeds and with severe exposure causes liver damage (Buckley et al 2007). Stabled racehorses today mostly lack the nutritional protection afforded a previous generation of horses. The impact has been noted clinically in the widespread increase in equine gastric issues and as stated by J.E. Anthony “Racing fans are missing about half of what they once enjoyed in racing.”

The role of the gut bacteria in the prevention of disease

The gut microbiome begins populating and diversifying from the moment of birth. Though ‘sterile’ in utero, gut derived DNA immediately drives immune health with exposure to nutrition. Recent research suggests that the gut microbiome can be stimulated by using proven probiotics with a track record in enhancing gut health (Barragry 2024). But it is the protective power of SCFAs to allow ‘cross talk’ between the lungs and the gut microbiome that is critical to supporting horses through their life span. 

Nutrition using grain ‘concentrates’ is currently at approximately  99% saturation in today’s equine population so a return to feeding ‘straights’ is a swim against the tide of modernity. But, knowing the influence of nutrition on health, performance and longevity it falls on horse owners to be mindful of the consequential  impacts  such convenience feeds have on the gut microbiome and immune system. Random supplementation and high starch feeds are leading to dietary health issues such as gastric ulcers, hyperinsulinemia and  hyperlipaemia (obesity) as well as increased risk of laminitis . So trust your gut and keep it simple – a diet of oats, flaxseed, a multi-vitamin balancer and ad lib hay will not only meet your horses’ energy needs but will keep them happy and healthy too.




REFERENCES

Barragry. TB (2024) WEB https://www.veterinaryirelandjournal.com/focus/254-alternatives-to-antibiotics-probiotics-the-gut-microbiome-and-immunity

Buckley T, Creighton A, Fogarty (2007)  U. Analysis of Canadian and Irish forage, oats and commercially available equine concentrate feed for pathogenic fungi and mycotoxins. Ir Vet J. 2007 Apr 1;60(4):231-6. doi: 10.1186/2046-0481-60-4-231. PMID: 21851693; PMCID: PMC3113828.

Budwig, Dr. J (1903-2008) WEB https://www.budwig-stiftung.de/en/dr-johanna-budwig/her-research.html

Chaucheyras-Durand F, Sacy A, Karges K, Apper E (2022). Gastro-Intestinal Microbiota in Equines and Its Role in Health and Disease: The Black Box Opens. Microorganisms. 2022 Dec 19;10(12):2517. doi: 10.3390/microorganisms10122517. PMID: 36557769; PMCID: PMC9783266. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9783266/

Holmes, R (2015) Feeding for stallion fertility. WEB 

https://www.theirishfield.ie/feeding-for-stallion-fertility-172113/

Judd A (1995) Flax - Some historical considerations. Flaxseed and Human Nutrition, S C Cunnane, L U Thompson. AOCS Press, Champaign, IL 1995; 1–10 [Google Scholar]

Martinac, P (2018) What are the benefits of flaxseed  lignans?  WEB https://healthyeating.sfgate.com/benefits-flaxseed-lignans-8277.html

National Research Council. 1989. Nutrient Requirements of Horses. Washington D.C.: National Academy Press.

Ralston, S VMD, PhD, ACVN (1994) The effect of diet on acid-base status and mineral excretion in horses in the Journal of Equine Practice. Vol 16 No. 7. Dept of Animal Science, Rutgers University, New Brunswick, NJ 08903

Seitz, A  (2022) What to know about starch_Medically reviewed by Seitz, A - MS, RD, LDN, Nutrition — WEB https://www.medicalnewstoday.com/articles/what-is-starch#benefits

Sonali Joshi, Sagar Mandawgade, Vinam Mehta and Sadhana Sathaye (2008) Antiulcer Effect of Mammalian Lignan Precursors from Flaxseed, Pharmaceutical Biology, 46:5, 329-332, DOI: 10.1080/13880200801887732