How quality of forage affects quantity of hard feed to be fed

The primary consideration when constructing a suitable diet for a horse is to determine its physiological status. One has to ask the question what is the horse doing; is it at maintenance (idle!), pregnant, lactating, working, undergoing rehabilitation, etc? All of these different situations will affect the animal’s total energy and protein requirements and thus proportionate forage/hard feed needs. Remember that supplying vitamin and mineral needs will have no real impact on quantitative feeding (g vs. kg!).

Forage quality. Fresh grass is the basic forage for most horses and it is also available in many conserved formats. Traditionally hay was the conserved forage of choice mainly for winter feeding. However, advances in agricultural machinery have resulted in the development of new grass cutting and preservation technologies. Originally silages were available in the form of clamped or big bale bagged silage. The production of plastic film led to wrapping grass bales of various sizes and shapes. Hay making was always heavily weather dependent so that a very high quality grass crop could be downgraded by poor weather. Nowadays grass can be cut when its nutritive value is high and rapidly conserved with minimum loss of quality. The nutritional value of any conserved forage depends initially on the quality of the parent material. Conservation cannot improve the original material but it can certainly lead to its degradation. So it follows the computer truth GIGO, which in computer science, means garbage in, garbage out! Quality will usually dictate how much hard feed is needed but this is not always the case as detailed below.

In the first instance I would like to compare different forages on the basis of their Digestible Energy (DE) content and their Crude Protein (CP) content expressed on a dry basis (DM) rather than on a fresh basis (see Table 1). This allows a direct comparison across different forages on a common basis without the complication of variable water contents eg., fresh grass contains say 80% water compared to only 15% in grass hay. Furthermore one can easily see the impact of choice of forage on hard feed requirements. For any given purpose, more hard feed will require to be fed if only the poorer quality forages are available. Thus, to state the obvious, a horse owner should always seek out the best quality forage in order to reduce both hard feed usage and the cost of feeding their horse. Exceptions are where obesity/laminitis are issues and soluble carbohydrate (sugar!) intake must be controlled. A coincidental benefit of maximising forage usage is that the horse receives a much more “natural” diet that ensures gut health. Table 1 gives the average nutritive values for the commonest forages fed to horses and if you do the arithmetic you will see that if you feed poor quality hay you must provide about 20% more hay to provide the same amount of energy intake compared to when good quality forage is fed kg for kg. In terms of protein, there is such a large difference between forages that the only way to make up any protein deficit is to feed a high protein concentrate or balancer since increasing the quantity of poor quality forage fed is, in many cases, impractical and will exceed appetite constraints.

Table 1: Forage characteristics


DE (MJ/kg DM)

CP (g/kg DM)

Young grass



Mature grass



Alfalfa, early flowering



Young grass silage



Mature grass silage



Maize whole crop silage



Good grass hay



Poor grass hay



Dried grass



Dried alfalfa



Feeding scenarios. Horses at maintenance should not require any hard feed in addition to forage. An exception might be when only very poor quality forage is available that is both low in protein and micronutrients. In this case an appropriate balancer or supplement should suffice. A 500kg horse fed the best quality conserved forage at 2% body weight (BW) as DM would consume about 160% of its energy requirement and thus would become fat. This perfectly illustrates the need to try to balance forage type to requirement and it also shows that no hard feed would be required. If only the best quality forage is available then intake will have to be limited to avoid obesity but from a welfare perspective this is not a good thing.

Horses/ponies in work need additional dietary energy supplies. As work intensity increases the contribution of forage to need becomes progressively less, simply because the animal cannot eat enough. Horses in hard work cannot accommodate the large volumes of forage that would be necessary to meet energy needs. Furthermore, a lot of forage would impose a burden on the horse in terms of non-functional weight or “ballast” and, as everyone knows, weight is a real handicap to horse performance. For a racehorse in full work even the very best quality forage can only be fed in limited quantities. A typical forage concentrate ratio would be 30:70 and thus the quality of the forage would have a negligible effect on the quantity of hard feed used; in this case, energy needs dictate the nature of the diet, not forage quality. A difference of 2MJ/kg DM would have little impact. However, at lower work rates and within appetite constraints, a high quality hay fed to a 500kg horse at the rate of 6kg DM/day would supply the energy equivalent of one kg hard feed more than if 6kg of poor hay were fed. Thus, quality forage can lead to savings in hard feed usage depending on the type of work done.

Yearlings that are being produced for the Thoroughbred Yearling sales are conventionally fed quite a lot of hard feed prior to the sales because the desired “finish/top line” cannot be obtained using forage alone. However, the contribution of forage to overall need will be affected by its quality and good forage could allow a saving in hard feed as in the example above.

Pregnant mares can do well on average forage alone in the early stages of pregnancy without the need for any hard feed. Of course, they should never be fed inferior quality forage at this stage. Hard feed usage at this time would be unusual. As the pregnancy advances space in the mares abdomen becomes restricted by the developing foetus and associated placenta so clearly conserved forage will have a limited usefulness. Of course, mares foaling in the natural season should be able to exist on fresh grass without recourse to hard feed. Doubts about grass quality in terms of micronutrients might suggest the use of a low-volume balancer/supplement.

Lactating mares have a relatively high requirement both for energy (2x maintenance) and protein (3x maintenance). Assuming a 500kg mare can eat 2.5% of its bodyweight (12.5kg DM) then poor quality hay would only supply ~80% of energy need and ~52% of protein need. In contrast, good hay would supply ~90% of energy need but only ~80% of protein need. It is clear from the foregoing that hard feed must be fed to the mare in early lactation to match need and that the quantity and character of the mix fed will be affected by the quality of the forage. For example, a higher protein stud mix would be needed to accompany poor hay compared to that needed for good hay.

It should be clear from the foregoing that forage quality significantly affects not only the quantity of hard feed but also its nutrient profile. In some notable cases, such as racehorse diets, the quality of the forage is almost irrelevant because so little can be fed and in some tropical and subtropical countries, very little forage is naturally available for feeding racehorses (West Indies, Hong Kong, UAE, etc). However, what is paramount in terms of forage quality is its hygienic status although this does not affect the quantity of hard feed fed!

Author: Dr Derek Cuddeford

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