forageForage is probably the most important component of your horse’s diet, whether you have horses in race or competition training, broodmares and youngstock, or simply ride for pleasure.

The significance of the right quantity and type of forage is easy to appreciate as health often fails when this is not achieved. Health issues can arise either when the level of forage fed is inadequate, the quality of forage is not good enough, or the digestibility is not appropriate for the life-stage or activity of the horses in question.

Forage should not be seen as a ‘filler feed’, or just something to keep a horse occupied between hard feeds, as it makes a very positive contribution to the overall ration. Making good choices with regards to forage will help to maintain digestive function, including gastric health, and can have a big impact on a horse’s ability to maintain bodyweight and condition. In addition, with a good forage regime respiratory health is easier to maintain and dentition can even be improved.

Forage contributes to the overall energy and nutrient content of a horse’s ration, but also helps to maintain digestive health through its physical effect on the movement of food through the gut, as well as through the retention of fluid within the digestive tract. In addition, plenty of forage can help preserve gastric health as saliva production is greater in horses chewing forage compared to concentrate feeds. Saliva contains bicarbonate, which acts to neutralize the acidity of gastric juices and so helps to protect the sensitive areas of the stomach from its corrosive effects. Forage also has a protective effect on the microbial balance within the hindgut, especially in horses fed a high starch ration such as those in competition or race training.

When choosing forage the main elements to consider are:

  • Good palatability to ensure adequate intake
  • A healthy intake to satisfy life stage or training requirements
  • Appropriate digestibility for the horse’s activity or life-stage
  • A profile of nutrients to complement concentrate feeds
  • Fitness to feed to maintain respiratory and other aspects of health

Forage palatability must be good to ensure intake

The best forage from a quality and nutritional standpoint is rendered useless if a horse will not eat a sufficient quantity on a daily basis. Practical experience can tell us a lot about what our horses like and what they don’t in terms of forage. Some horses appear to prefer softer types of hay, whilst others prefer more coarse stemmy material. Many horses will readily consume haylage, whilst others may prefer traditional hay. Apart from the physical characteristics, the sugar content of hay or haylage may affect its palatability. Forage made from a high sugar yielding Ryegrass is likely to have a higher residual sugar content compared with that made from more fibrous and mature grasses such as Timothy. Whilst most horses will eat many forage types when they are in light work, appetite always comes under pressure as the level of work increases. A highly palatable forage, whether hay or haylage, is therefore essential for any horses in hard work.

Top tip for encouraging forage intake

Research suggests that offering more than one type of forage can help to increase the overall amount of forage eaten per day. For example, good clean hay could be offered together with some haylage, or with a suitable container of alfalfa based chaff or dried grass. This allows horses to mimic their natural behaviour and browse between the different forage types.

What is a healthy intake of forage?

A hot topic for discussion is always what to aim for in terms of daily forage intake. More is almost always better as far as forage intake is concerned, but there are a few issues to be aware of.

Typically the absolute minimum amount of hay fed should be about 1% of bodyweight, but this rises to between 1.2-1.5% of bodyweight when feeding haylage, as the latter has a higher water content compared to hay. Traditional horse haylage may contain between 25-40% water. Horses in high intensity work are often fed near to the minimum recommended level of forage, but it is always a good idea to try to feed a little more, which helps reduce the risk of compensation by overfeeding concentrate feeds.

Fig 1 – Intake of haylage needed to achieve a similar dry matter intake to 5kg of hay
MoistureDry MatterWeight of forage% Increase above hay
Hay (Average)15%85%5kg
Haylage 130%70%6kg20%
Haylage 245%55%7.5kg50%

For horses in less work the minimum amount of hay offered to stabled horses should be nearer to 1.5% of bodyweight. For some leisure horses, it is possible to feed a ration that is almost exclusively forage, in conjunction with suitable feed supplements to ensure that the ration remains well balanced. For horses at grass, that are either stabled overnight or fed forage in the field, it can be offered on an ad libitum basis. Most horses will self-limit their forage intake, although some horses as well as good do-ers will need to be restricted to prevent them from becoming overweight.

Fig 2 – Forage intake according to percentage bodyweight (As fed basis)
1% bodyweight1.5% bodyweight1.25% bodyweight
250kg Pony~2.5kg~3-4kg~3.0kg
500 kg Horse~5.0kg~7-8kg~6-7kg

Most nutritionists accept that even for performance horses feeding more forage should be encouraged, as this contributes towards maintaining their digestive health and psychological well being. However most racehorses in training are only offered what would be considered the minimum amount of forage to maintain gastrointestinal health, largely due to appetite constraints or due to concerns over gut fill hampering race performance. In some instances, the amount of forage a racehorse will eat is limited due to appetite, especially where they are being over fed with concentrate feed, or where unpalatable forage is being fed. Establishing a healthy daily intake of forage during the early stages of training and then maintaining this level through the season is therefore very important.

What is the gut-fill effect?

Any feed, whether forage or concentrate, increases ‘gut fill’, or in other words the weight of feed held within the digestive tract. However forage by its very nature is bulky and tends to stay in the hindgut for longer, as it is digested more slowly through the process of fermentation. In addition, the fibre within forage physically holds onto water within the hindgut, which increases the weight held within the digestive tract further.

A horse carrying excess weight, either in terms of body fat or gut fill, is not going to perform to its best in high intensity events such as racing, where power to weight ratio is important. Racehorse trainers have historically been aware of this ‘gut fill’ factor and this largely explains the tradition of reducing access to forage prior to racing. Whilst it may be advantageous to reduce forage intake in the 72 hours prior to racing, it is important not to allow forage intake to go below the minimum of 1% of bodyweight. Reducing forage intake excessively can have a negative impact on gastric health, especially in horses that are prone to gastric ulceration. The presence of feed, particularly forage, in the stomach helps to ‘cap’ the gastric fluids reducing their contact with the non-glandular region of the stomach, which is so prone to ulceration in some horses. An empty stomach allows gastric fluid to aggravate any pre existing mucosal inflammation or gastric ulcers. Reducing forage at this time of heightened stress can also adversely affect hindgut health, potentially increasing the risk of digestive disturbance including colic.

Not all fibre sources have the same impact on gut fill, however, and generally the more easily a fibre is digested, the shorter the time it will be held within the digestive tract and the more quickly the associated water will be reabsorbed. For example, mature Timothy hay, is likely to be less digestible than early cut Ryegrass hay or haylage. Alfalfa hay or chaff is also more digestible and has been shown to hold less water within the digestive tract due to the nature of its fibre content.

Top tip on gut fill

Whist it is inadvisable to make any sudden changes to the type of forage fed, there is scope during the few days before racing or intense competition, to increase the relative proportion of digestible hay / haylage. For example, a trainer that is feeding Timothy and alfalfa may reduce the Timothy slightly and increase the alfalfa 3 days prior to racing / competition.

For horses competing in long slower exercise such as endurance, the presence of fibre and associated water in the gut is a significant advantage and so forage intake in these horses tends to be much higher. In this instance, the water associated with fibre in the hindgut acts as a short term reservoir that can be drawn on during competition to offset dehydration.

How much forage in relation to concentrate?

The ratio of forage to concentrate fed in a daily ration is also important. The main elements to consider when establishing this are dietary energy requirement, appetite and the relevance of gut fill. In general, where energy requirement is low forage to concentrate ratio can be high. However, where energy requirement per day is higher the forage to concentrate ratio is usually reduced. In horses with a high energy requirement e.g. mares in early lactation, or racehorses where appetite may be limiting, a lower forage to concentrate ratio can be necessary in order to achieve the desired overall daily energy intake. In some horses or ponies such as that are prone to ‘tying up’, gastric ulcers, or laminitis it can be desirable to limit starch and sugar intake from concentrate feed and so in this instance a higher forage to concentrate ratio is advised.

Fig 3 – Typical forage to concentrate ratios for different horses
Typical Energy Intakee.g. suitable Forage: Concentrate
Leisure HorsesLOW90:10
Box restersLOW90:10
BroodmaresHIGH60:40
Endurance horsesHIGH70:30
Competition horsesMOD / HIGH60:40
Race horsesHIGH50:50
Low starch dietVARIABLE80:20

Nutritional Considerations

nutritionThe nutritional contribution made by forage should not be underestimated and should be complemented by any associated concentrate feed. Forage composition and digestibility is affected by the type of grasses present, the maturity at harvest and also the underlying mineral composition of the soil on which it was grown. There is therefore great diversity in the nutritional composition of forage on a worldwide basis.

The main factors that will influence the energy content of forage include the nature or digestibility of the fibre present, the level of hydrolysable carbohydrate (usually sugar), and the protein and oil content. Forage digestibility is the main determinant of its energy content and the higher the digestibility the greater the energy contribution is likely to be. The energy content of early cut forage is generally higher than that of mature later cut material due to its digestibility being better, but this will depend to an extent on the grasses present. Ryegrass hay, for example, is likely to have a higher digestibility than timothy hay cut at a similar level of maturity. Equally legume hays such as Alfalfa or Sanfoin also tend to have a higher digestibility than grass species.

Forage also contributes significantly to a horse’s protein intake, but again varies greatly in its protein content. There is a clear relationship between maturity at harvest and the true protein content of forage.

Percentage protein tends to fall through the growing season, as the forage grows and becomes more mature. There are also differences in protein digestibility between forage types and once more legume hays such as alfalfa offer superior protein content and digestibility. The sugar content of forage contributes to energy provision, but can also impact on palatability and in terms of haylage manufacture on the ability to establish a good fermentation within the bales following harvest. Sugar content is affected by grass species and harvesting conditions including time of day and relative sunshine.

The macro and micro mineral composition of forage tends to reflect the underlying geology of the soil on which it was grown, but again there can be subtle differences between grass species. Generally forage should not be relied upon to make a significant contribution towards micro mineral intake, although any major deficiencies or excesses are very relevant. For example, some forage in particular parts of the world may be very low in copper, or equally very high in selenium or iron and this is important information to allow an overall balanced ration to be provided.

In terms of macro mineral nutrition, it is important to ensure that the calcium and phosphorus content of forage complements the concentrate feed. Legume hays such as Alfalfa are a rich source of bioavailable calcium, which can be useful especially in cereal based rations to help balance phosphorus intake. However, excess calcium intake can be an issue where alfalfa is used as the sole source of forage and therefore it is often used in conjunction with other forage types.

Forage should always provide the foundation upon which a ration is based and so choice of forage should reflect the overall intentions of the diet. For example, a racing ration needs to satisfy the higher energy and protein requirements of these horses. It therefore makes logical sense to use higher digestibility forage that delivers more energy and protein. This then means that concentrate feed can be fed at a sensible level to make up the shortfall in energy and nutrient requirements. Too often low digestibility forage is used for performance animals in the belief that all they require is a source of fibre and this leads to a necessity to feed a high intake of concentrate feed to make up the shortfall. In contrast, horses or ponies with a lower energy requirement such as those in light or no work, or those that are box rested can be fed forage with a lower digestibility and energy content. This allows these animals to be fed a satisfying level of forage, which helps to meet their psychological need to chew.

Purchasing hay – getting it right

When purchasing hay, how can we gain insight into the likely nutritional content of the forage concerned. Firstly and most simply the type of grasses present and the cutting stage of the hay will offer some information as described above. This is information that your forage merchant should be able to provide. Secondly we can undertake a visual assessment ourselves, giving some further information on suitability.

Visual analysis of forage, a few factors to consider:

Maturity
The more mature or later forage is cut, the greater the amount of low digestible fibre it contains, and the more stemmy and unpalatable it becomes. Look out for the proportion of seed heads present to give an idea of maturity.
Leaf present
The more leaf present within forage, the higher the likely nutrient content since many of the nutrients are concentrated in the leaves, where photosynthesis occurs.
Colour
Generally the greener the forage, the better.
Smell
The smell of hay can give you a very rough idea on the cleanliness to feed in terms of moulds and dust content. This is not a foolproof method of assessing this and laboratory analysis is more reliable.
Foreign materials
Always check for any contaminants such as poisonous plants e.g. ragwort, or field debris such as sticks or wire which could cause injury. A high presence of weeds such as thistles decreases the overall quality of the forage

A further option, especially when large batches of hay are being purchased at one time, is to embark on some laboratory analysis which will give much more information. This analysis may extend to a basic nutritional profile and fitness to feed assessment in terms of microbiology, or could involve a full nutritional analysis including macro minerals, micro minerals and vitamins. The first step towards laboratory analysis is to obtain a representative sample from your batch of hay or haylage. Ideally a hay corer should be used so that many bales can be sampled to form a mixed sample. Any bales of haylage sampled should always be resealed with suitable tape as soon as possible. Grab samples taken by hand mixed together and then sent to the laboratory, although if only a few bales are sampled the results may not be as representative. All forage samples should be put into a re-sealable plastic bag and the air expelled before delivery to the laboratory as soon as possible. The laboratory may offer some interpretation of results, but consulting a nutritionist or your feed or supplement company for help can be a good idea.

Fig 4 – Typical nutrient analysis of forage
AnalyticalDescriptionComment
AnalyticalDescriptionComment
Dry matter (DM)Measures the % of material remaining after all the water is removed.Useful analysis for haylage. Gives an indication of likely mould growth when DM is reduced.
Crude Protein %How much protein is present, but also any non protein nitrogen residue from fertiliser.Gives and indication of stage of growth and feed value.
NDF %A measure of the plant’s cell wall content. The higher the NDF value, the less hay the horse will eat.Useful to predict horse’s likely voluntary intake as when NDF is high intake is low.
ADF %A measure of the highly indigestible plant material present in forage including cellulose, lignin, and silica.Useful for helping to predict likely digestibility as Low ADF values mean higher energy value and digestibility.
Ash %How much macro and micro mineral is presentGives an overall view of mineral content but further analysis of micronutrients needed for more information on individual elements
WSC %Sugar and fructan content of forageUseful analysis where horses are prone to either laminitis or tying up
Relative Feed ValueA high RFV reflects higher quality, greater intake and higher digestibility.Fewer concentrates will be needed to supplement the diet when RFV is high.

Hay or haylage analysis can be very difficult to interpret and some guidance is often needed on what constitutes forage of good, average or poor feed value.

The Hay Market Task Force of the American Forage and Grasslands Council classifies forages using a quality scale. These standards apply to forages comprised of legumes, grasses, or legume-grass mixtures. These values can be useful to compare your hay against to assess its nutritional quality. All of the values are quoted on a dry matter basis, with prime being the best quality and 5 being of the lowest nutritional quality.

Fig 5 – Hay quality standard (Hay Market Task Force of the American Forage and Grasslands Council)
Hay qualityCrude protein (% CP) DMAcid detergent fibre (%ADF) DMNeutral detergent fibre (% NDF) DMRelative feeding value
Prime> 19< 31< 40> 151
117 – 1931 – 3540 – 46151 – 125
214 – 1636 – 4047 – 53124 – 103
311 – 1341 – 4254 – 60102 – 87
48 –1043 – 4561 – 6586 – 75
5< 8> 45> 65< 75
Table 6 – Positives and negatives of different types of forage
PositivesNegatives
Hay from colder climates e.g. UK, Ireland
Usually palatableQuality can be variable
Economical
Hay from warmer climates e.g. USA / Canada
Usually very cleanPremium price
Feed value often higher, may need to adjust hard feed
Usually palatable
Haylage
Usually cleanDry matter can be variable
Fermentation inhibits mould growthNeed to feed more than hay
Feed value often higherBeware of punctured bales
Usually palatableProduced regionally
Alfalfa (High temperature dried or sun dried)
Good adjunct to forage (e.g. 1-2kg)High intake can oversupply protein and calcium
Can be used as chaffLeaf fragments can add to dust
High feed value & digestibility
Less gut fill

Whilst establishing nutritional quality is important, of equal significance is the cleanliness of hay and haylage given their potential as a source of mould, dust and mycotoxins for horses. Let us know consider the fitness of forage to be fed to horses.

Fitness to Feed

Quality of forage, in terms of its mould, yeast and mycotoxin load, can have a major impact on respiratory and wider health. Inflammatory airway disease in horses has a great impact on horse health and in performance horses results in loss of training time and therefore affects potential earnings. There is also the associated cost of veterinary treatment involved. A large proportion of competitive horses including racehorses may experience some form of airway inflammation during their competitive lives. Poor quality forage has been described as significant risk factor in the development of airway inflammation. Moulds such as Aspergillus fumigatus, Thermoactinomyces vulgaris and Micropolyspora faeni have been implicated in the development of respiratory disease in horses. Exposure to spores from these moulds may bring on an IgE driven allergic or hypersensitivity response in susceptible horses which involves inflammation of the small airways.

Hay that has heated during storage, or that has been bailed with a high moisture content is more likely to have a higher load of these undesirable microbials. Other bi-products of mould metabolism that can also have a detrimental effect on horse health are mycotoxins.

Forage can be a source of mycotoxins?

Mycotoxins are chemical substances that are produced by moulds that may be present on forage. However, equally they can also be found in concentrate feed, bedding, or more generally in the stable environment. Mycotoxins can be formed by moulds in the field prior to the forage being harvested, or subsequently during storage. The level and type of mould / fungus and associated mycotoxins produced are largely dependent on the environmental conditions and so it is not surprising that different mycotoxins are more prevalent in different parts of the world.

Horses can ingest, inhale or even absorb mycotoxins through their skin. Exposure to mycotoxins has been shown to contribute to disease. There are estimated to be over 300 types of mycotoxins produced by a large number of moulds or fungi, but the three most significant ones for horse health are Fusarium, Pencillium and Aspergillus.

Do mycotoxins represent a health hazard to horses?

There is no doubt that mycotoxin exposure in horses can affect horse health, although the incidence of severe mycotoxin derived disease is rare. Mycotoxins are prevalent in our environment and are almost impossible to totally eliminate, however, from the horse’s perspective the important factor is to try to limit mycotoxin exposure as far as practical.

Mycotoxicosis can be characterised by poor appetite, failure to thrive, immune suppression, liver damage, and increased incidence of secondary infections. However, many of these symptoms could also be attributed to other conditions.

The risk of mycotoxicosis in horses from forage remains unknown at the current time, as we do not know how widespread the contamination of forage is with mycotoxins, or indeed what the clinical relevance is of chronic low grade mycotoxin intake to health and performance. Whilst the exact risk of mould or mycotoxin contamination of forage is unknown, it is sensible to take active steps to reduce the exposure of horses.

Management strategies

Purchasing good quality and clean forage from a respiratory perspective will certainly reduce the pressure placed on horses’ respiratory systems.

Microbiological Analysis
Ideally where batches of hay are purchased a laboratory analysis for moulds would be carried out prior to delivery. The laboratory will usually give guidance on the interpretation of the microbiology results, although as a rule of thumb the lower the result (CFU/g) the better. Whilst a very low mould (<10-100 cfu/g) should not usually cause concern, more deliberation on purchase of a batch of forage should be triggered by a mould result that reaches 1000-10,000 cfu/g. Certainly a cautionary approach should be taken if any appreciable levels of Aspergillus mould species are identified. Aspergillus Fumagatus has particular association with respiratory disease including ‘Farmers Lung’ in humans.
Storage
A suitably sized storage area will allow storage of a good-sized batch of your chosen forage giving consistency through the winter or racing / competition season. Ideally there will be enough storage to ensure that batches of forage can be sampled and sent to the laboratory prior to purchase.
Forage merchant or farmer
A good working relationship with one or more farmers or forage merchants is essential to be able to consistently buy good forage. They need to know what you want to buy and you need to be able to rely on them to provide a high quality product through the season.
Soaking or steaming hay
Studies have shown that both soaking and steaming reduce the burden of moulds in forage efficiently. In order to soak hay effectively it needs to be totally submerged for at least 20 minutes, but prolonged soaking can leach out important nutrients such as sugars and some minerals. Steaming is becoming more popular and commercial hay steamers may it significantly more practical.
Mycotoxin binders
Unfortunately, mycotoxins are relatively resistant to chemical or heat treatment and so once they have been formed, they are a challenge to remove from forage. Mycotoxin binding supplements, which are often derivatives of yeast, clay, aluminosilicates or zeolites can be added to the feed in an attempt to prevent the absorption of mycotoxins from the digestive tract. These supplements can be top dressed onto feed, although some concentrate feed companies already add mycotoxin binding agents to their formulations.

Summary

In summary, much emphasis is placed on finding an optimum concentrate feed and associated supplements, to enhance the diet of horses whether they are competition, race or leisure horses. The same emphasis should ideally be placed on the choice of forage as it can so easily make or break the most well thought out feeding plan.