By Dr Catherine Dunnett
Too often thought of as just a ‘filler’, or occupational therapy to while away the time between hard feeds, forage is worth so much more than that. Simply feeding an inadequate quantity of forage, or choosing forage that has an inappropriate nutrient profile, or is of poor quality can have a negative impact both on health and performance in racehorses.
Inappropriate choice of forage and its feeding can easily lead trainers down the slippery slope towards loose droppings and loss of condition. Forage can also have a significant impact on the incidence and severity of both gastric ulcers and respiratory disease, including inflammatory airway disease (IAD) and recurrent airway obstruction (RAO).
When choosing forage the main elements to consider are
• Good palatability to ensure adequate intake
• Adequate digestibility to reduce gut fill
• Fitness to feed to maintain respiratory health
• A profile of nutrients to complement concentrate feeds
FORAGE CAN ONLY BE GOOD WHEN PALATABLE
Palatability is a key issue, as even the best forage from a quality and nutritional standpoint is rendered useless if the horses do not eat sufficient quantities on a daily basis. Palatability is a somewhat neglected area of equine research and so we largely have to draw on practical experience to tell us what our horses like and what they don’t. Some horses appear to prefer softer types of hay, whilst others prefer more coarse stemmy material. Many horses readily consume Haylage, whilst some trainers report that other horses prefer traditional hay. Apart from the physical characteristics, the sugar content of hay or haylage may affect its palatability. Forage made from high sugar yielding Ryegrass is likely to have a higher residual sugar content compared with that made from more fibrous and mature Timothy grass.
Some interesting research carried out a few years ago by Thorne et al (2005), provided some practical insight into how forage intake could be increased in the reluctant equine consumer. This work reported that the amount of time spent foraging (which will increase saliva production), was increased when multiple forms of forage were offered to horses at the same time. From a practical viewpoint this can be easily applied in a training yard and it should help to increase the amount of forage consumed. For example, good clean hay could be offered together with some haylage, and a suitable container of alfalfa based chaff or dried grass all at the same time.
A Healthy Intake
Racehorses in training often eat below what would be considered to be the bare minimum amount of forage to maintain gastrointestinal health. Whilst sometimes this is due to the amount of forage offered being restricted, in other instances it is because the horses are limiting their own intake. This may be due to either their being over faced with concentrate feed, or due to unpalatable forage being fed. Establishing a good daily intake of forage during the early stages of training and then maintaining the level through the season is important. Typically the absolute minimum amount of forage fed should be about 1% or 1.2-1.5% of bodyweight for hay or haylage, respectively. This equates to 11lb of hay or a rounded 15.5lbs of haylage for an average sized horse (1100lbs). The weight of haylage fed needs to be greater than that of hay due to the higher water content of the latter.
Intake of haylage needed to achieve a similar dry matter intake to 11lbs of hay
Moisture Dry Matter Weight of forage Percentage Increase above hay
Hay (Average) 15% 85% 11lbs
Haylage 1 30% 70% 13lbs 20%
Haylage 2 45% 55% 16.5lbs 50%
The dry matter of haylage needs to be consistent to allow a regular intake of fibre and reduce the likelihood of digestive disturbance or loose droppings. Ideally trainers should be aware of any significant change in dry matter, so that they can adjust the intake accordingly.
Forage intake is restricted in racehorses to firstly ensure that a horse consumes adequate concentrate feed to meet their energy needs and requirement for vitamins and minerals within the limit of their appetite. Secondly, the amount of forage fed is restricted in order to minimise ‘gut fill’ or weight of fibre and associated water in the hindgut, as this will restrict their speed on the racetrack.
BUT… inadequate amounts of forage in a horses’ diet has such a negative effect on health that the minimum amount fed must be kept above recognised ‘safe limits’. Choosing an early cut forage that is less mature and with more digestible fibre means that the ‘gut fill’ effect is lessened. In addition, horses can always be fed more forage during training with the daily quantity being reduced (within the safe limits) in the few days before racing where this is practical.
FITNESS TO FEED
Quality of forage, in terms of its mould, yeast and mycotoxin load, can have a major impact on respiratory health. A recent Australian report (Malikides and Hodgson 2003) highlighted the cost of inflammatory airway disease (IAD) in horses in training, in terms of loss of training time and of potential earnings, together with the associated cost of veterinary treatment. They estimated from their study group that in Australian racing up to 33% of horses in training can have lower airway inflammation, yet show no overt clinical signs.
Type and therefore quality of forage, as well as the quality of ventilation were singled out as the most significant risk factors in the development of IAD.
Forage is potentially a concentrated source of bacteria, mould spores and even harvest mites. Hay that has heated during storage, or that has been bailed with a high moisture content is likely to provide a greater load of these undesirable agents that can harbour substances that promote airway inflammation, such as endotoxin.
Purchasing good quality and clean forage from a respiratory perspective will certainly reduce the pressure placed on young racehorses’ respiratory systems. However, how does one achieve this?
• Microbiological Analysis – the price paid for a microbiological analysis of a prospective batch of hay is a worthwhile cost when the consequences of poor hay are considered.
Assuming the analysis is favourable, purchasing a larger batch for storage gives further peace of mind and spreads the cost further, providing of course that the storage conditions are appropriate.
Interpretation of the microbiology results as CFU/g (colony forming units/gram) for moulds, yeasts and Thermophillic actinomycetes is not difficult. As a rule of thumb the lower the CFU count the better. Whilst a very low mould or yeast count (<10-100) should not usually cause concern, more consideration of the merits of a batch of forage should be triggered by a CFU count that reaches 1000-10,000. Certainly if any Aspergillis species of mould are identified the alarm bells should be ringing. Aspergillis Fumagatus has particular association with respiratory disease including ‘Farmers Lung’ in humans.
A suitably sized storage area will allow storage of a good-sized batch of your chosen forage giving consistency through the season. It makes financial sense for the welfare of racehorses to make adequate provision for a good-sized storage area. Third party storage is also sometimes an option where this is not available on site.
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 hay. 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.
Forage merchant Robert Durrant stands by the principle that “A good forage merchant should be able to supply a trainer with the same high standard of hay for much if not all of the season”.
He adds that in his opinion “American hay English hay or haylage are all good options when they have been made well and the quality is high, but the quality of the American hays are consistently more reliable.”
The nutritional contribution made by forage should complement that made by the concentrate feed. Most racing rations are high in energy, high in protein and low in fibre. Therefore a suitable forage needs to be contrastingly high in digestible fibre with a limited level of energy and protein. However, where you have sourced early cut hay or haylage that is more digestible and higher in energy and protein, the concentrate feed intake should be adjusted to account for this. This will help to avoid the issue of over feeding of energy or protein. An excess of energy can result in undesired weight gain or over exuberance, whilst an excessive intake of protein at the very least increases the excretion of ammonia, which is a respiratory irritant. Whilst it is important to know the calcium and phosphorus content of forage, the trace mineral content is less significant as the concentrate feed will meet the majority of the horse’s requirement. The exception to this, however is where a batch of forage is identified as having a severe excess of one particular element, e.g. Iron which can reduce the absorption of copper.
Much emphasis is placed on finding an optimum concentrate feed and associated supplements, to enhance the diet of horses in training. The same emphasis should ideally be placed on a trainer’s choice of forage. Forage can so easily make or break the best thought out feeding plan.