By Derek Cuddeford
Senior Lecturer at the Royal (Dick) School of Veterinary Studies at the University of Edinburgh. He has had a long term research programme investigating the nutrition of horses and recently has been measuring the voluntary feed intake of roughage by horses.

All horses need fibre and the preferred source is long fibre, commonly referred to as forage, but more correctly described as roughage. The traditional source of roughage for horses is grass but this is not available all year-round in Northern Europe because of low winter temperatures, or in Southern Europe because of high summer temperatures! Thus, there is a need to conserve grass as hay, silage or haylage in order to be able to supply roughage to the horse when fresh grass is unavailable. This situation applies to non-competitive horses that are kept outside for most of the time. In contrast, most high performance horses are housed and rely on conserved roughage. The performance horses have high requirements for energy that is unable to be met from roughage alone and furthermore, fresh grass has no real role in their diet as it contains minimal dry matter (DM <20%) and thus would be too bulky. A large gut volume represents non-functional weight and thus, it would be a handicap to a racehorse that relies on its muscle bulk for movement.

If we take the racehorse as an example of the ultimate performance horse, it is interesting to see what roles roughage can play in terms of the animal's well-being. All of these animals depend on having a fully functional respiratory system and the slightest compromise to this can result in lost races; therefore, constant peak fitness is essential. It is essential to have high hygiene levels within the stable.   Two sources of respiratory challenge exist; that from the bedding and that from the food. Environmental contaminants associated with bedding are controllable as are those from food. In terms of the latter, hygiene status of the roughage is more important than its nutritional value. In many countries, it is impossible to make hay that is of a sufficient standard not to compromise respiratory function. It is for this reason the demand for "clean" roughage in the form of haylage has increased and now many racehorses are fed this roughage. Hay suffers the dual disadvantages of being both dusty and mould-contaminated. The latter giving rise to spore production and associated allergic reactions in horses fed such material. Well-fermented haylage is both free of dust particles and mould.

In hot climates, as little as 2kg of roughage may be fed daily to a 500kg horse, although in temperate climates, 4kg of dry roughage would be more usual. These quantities of roughage would supply between 10 and 20% of the racehorses energy requirement. For example, 4kg of dry feed would provide 3.4kgDM to the horse. If haylage were substituted for the hay then the fresh weight required would depend on the DM content of the haylage. For example, a 50%DM haylage would require to be fed at the rate of 6.8kg/day whilst a 70%DM haylage should be fed at nearly 5kg/day. Underfeeding haylage to racehorses is a common problem that can contribute to a greater incidence of colic due to lack of fibre and to muscular problems arising through a reduced supply of potassium. Thus, it is essential to know the DM of the haylage to enable correct rationing of the roughage. The use of haylage can increase the contribution that the roughage makes to the energy supply. For example, haylage made from quality grass (ryegrasses) cut at the right stage of growth (ear emergence) can contribute up to one third of the horse's energy needs thus reducing their reliance on cereals. The high digestibility of the haylage means there is no building of a large gut, as it will be degraded rapidly, but as the market matures, producers of horse haylage realise they must achieve high quality standards for their product to be accepted by the increasingly knowledgeable end user. Many producers now have contracts to supply racing yards throughout the year where there is no room for error! This developed expertise has benefited the wider community of horse owners in that generally, horse haylage can now be regarded as quality roughage fit for all horses.

Rules to follow in selecting haylage:
1. Know the DM (50-70);
2. Know the pH (4-6);
3. Look for ryegrass-dominated samples;
4. Should have a pleasant smell with no indication of ammonia (ammonia nitrogen <3%);
5. No sign of basal plant material/soil contamination (ash content <8%);
6. Plenty of leafy material, not dominated by stalk;
7. Intact packaging;
8. Eight bale wraps;
9. Preferably white plastic film.

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