Feeding the sport-horse on forage

But even as an athlete, the horse remains a herbivore destined to eat grass. A diet which is too high in fermentable glucose (starch) has several drawbacks, with regard to the horse’s health, well-being, and performance. Recent advances in equine research over the last few years show that a sport-horse’s requirements can be satisfied by feeding on forage, without it being detrimental to performance. Certain helth and well-being advantages can also be noted. As the saying goes : « anima sana in corpore sano » meaning that when the horse is in good bodily health,  he will also be in good mental health !

The horse is a monogastric herbivore with a digestive system suited to getting the most from fibrous matter. The horse’s stomach and small intestine are small in size compared to the large intestine which is well developed. These anatomical particularities mean that the horse in a natural environment has to graze in small quantities all day long (~ 15 hours per day). Therefore, a feeding diet based on large quantities of hard feed goes against nature. This then leads to risks for the horse’s health and well-being. Especially when the forage provided is insufficient (sometimes even non-existant) and that periods between feeds are prolonged (> 6 hours).

In the case of high energy content feeds, the feed spends a long time in the stomach and small intestine. The amylolytic bacteria in the stomach microbial ecosystem have time to ferment the starch into VFA (volatile fatty acids) and a lactate, componenets which decrease the gastric pH.  The horse is therefore in a state of acidosis. The stomach mucous lining, particularly the squamous mucosa (top area) which does not secrete any protective mucus, is then subjected to agressions which can lead to the appearance of gastric ulcers.

Lack of fiber in the horse’s diet is a factor of risk in the appearance of ulcers. As the horse chews less, saliva production (saliva is a substance with a neutral pH) decreases, and with it the buffering effect for the continuous production of hydrochloric acid in the stomach.

Even if the prevalence of gastric ulcers can be noted in sport or race horses, a high starch diet and/or a diet too low in fiber content can also cause the onset of other digestive disorders. There is a threshold amount of starch which when overshot causes a-amylase (enzyme to break down starch) to become saturated in the small intestine. The excess of unbroken-down starch then travels to the large intestine, designed to digest fiber, and incaple of digesting starch efficiently. The amyolitic bacteria will then ferment the starch to become lactate and VFA, while acidifying the large intestine. This acidity is harmful to the intestinal microbiota balance which intervenes in the digestion of fiber. A horse can suffer from a lack of appetite, sometimes even weight loss, which can in turn lead to serious health issues (bouts of colic or laminitis….) which will all ultimately lead to a decrease in performance.

All this is without forgetting behavioural problems (stereotypical behaviour) linked to boredom when the horse is stabled with nothing to eat (crib biting, weaving, annoyance…). These disorders can also have an impact on the horse’s health and performance level.

Jansson and Lindberg (2012) have for example tested a diet based solely on haylage harvested early in the season (providing 13 to 17,4 kg of haylage/ horse/ day, haylage which has a high energy content) supplemented with a vitamin and mineral supplement (VMS) tested on Standardbred horses. The results showed that the horses performance was not affected by this diet, compared to a more « classical » diet based on hard feed with a high starch content :

• V4 speed (speed at which the anaerobic threshold is reached, corresponding to a 4mmol/L lactatemia level), plasmatic glucose rate and pH in veinous blood during highest exertion level ;
• Despite a slightly lower muscle glycogen rate after effort.

These indicators demonstrate better aptitude to sports for the horses fed exclusively on high energy content forage.

Ringmark et al. (2017) tested the effects of the intensity of training on Standardbred colts and fillies provided with a diet based 100 % on haylage given ad lib, supplemented with a VMS. The results demonstrated that on this diet, the difference in the intensity of the training programme had no effect on ingestion, growth and muscle glycogen rate in these horses.

In both studies, the horses fed exclusively on high energy forage were as a general rule less inclined to be subject to digestive or behavioural disorders than horses in the control groups, fed on a substantial part of hard feed in their ration.

As we’ve just seen it is quite possible, and even recommended, to feed a sports horse on forage. How should one go about reasoning the part attributed to forage in the horse’s diet ?

Knowledge of your horse’s requirements

Knowing your horse’s nutritional requirements is the first step to satifying them. There are different elements to consider :

• Energy requirements (expressed in Horse Forage Units or UFC in French) ;
• In Protein (expressed in Digestible nitrogen matter for horses or MADC in French);
• In minerals and vitamins.

The latter depend on the animal’s characteristics (size and weight, age and gender) and the level of physical, activity.

Reference information is available in the INRA chart 2012 (Martin-Rosset et al., 2012)

Carry out an inventory of the forage resources available

It is essential to carry out an inventory of the forage resources available so as to put them to good use. Depending on the animals’ requirements, the types of forage (hay, haylage, and silage), the available amounts and especially the quality, the quantities to provide will be different. Having a specialized laboratory carry out a chemical analysis of the forage is essential to know what the nutritional value of the forage is, and to be able to adjust the horse’s ration according to his requirements.

Adapting the amounts provided to suit the individual horse’s needs

Step 1 = Cover the horse’s requirements as much as possible by feeding forage

Amount of forage

In general, the recommendations regarding the minimum amounts of hay to be fed daily are between 1,5 and 2 % of his live body weight, which is around 10kg of hay/ horse/ day for a 500kg animal. This quantity depends, of course, on the animal’s characteristics, the dry matter (DM) content but mostly on the quality of the forage. This quantity can therefore vary between 9,0 and 15,5 kg of DM/ horse / day according to the animal and the type of forage.

Quality of the forage used
The quality of a forage corresponds to its nutritional value. There are two controlable parameters which enable to improve the quality of forage ::

• The stage at which it is harvested : the younger the grass, the better the nutritional value (sugar / protein content). For horses with high needs, priority should be given to forage harvested early on.
• The composition : (plant species) : leguminous plants have a  high protein content. Forage containing these plants can be used to supplement a ration which is lacking in protein.

Stage 2 = Supplementing with concentrated feed, only when necessary !

When the forage resources, either because of their quantity or their quality are not enough to cover the entirety of the horse’s needs, hard feeds can be used as to supplement.  It is important to calculate a balanced ration to adapt the quantity and quality of the concentrates according to the quality of the forage distributed, because the reverse is more complicated!

When the forage ration is fractionned, the evening ration should be greater to keep the horse occupied for the best part of the night.

Management of feeding practices over time prior to considerable physical exertion (competition, intense training session…) is a factor to be taken into account. The distribution of forage should be reasoned so as to not be detrimental to the horse during the effort, but neither should effort be undertaken on an empty stomach. As demonstrated above, one can readily understand the risks linked to total absence of feed. Pagan and Harris (1999) recommend giving a small quantity of forage (between 1 and 3kg of hay/ horse) in the few hours prior to an effort. This type of practice has no influence on the animal’s sports performance, and enables to prevent the risk, amongst others, of gastric ulcers.

Advantages

Most of the advantages of a diet based on forage have already been presented above (better respect of the horse’s digestive physiology and well-being…). Economically speaking, feeding in majority on forage means up to 50 % saving on the horse’s ration.

Drawbacks

The quality of forage remains however variable and difficult to control (from one field to the next, and even within a same plot of land, from one year to another). It depends on numerous factors (climate conditions, harvesting, drying and storage methods and conditions…) which can all make this type of diet uncertain. A laboratory analysis is therefore essential to determine the nutritional value of the forage provided (Forage units, Digestible nitrogen matter and total nitrogen matter) and to establish a balanced diet.