Forage means different things depending on the context. For herbivores it is a description of their grazing and this can cover a bewildering array of materials across species and environments. Closer to home, in livestock production, it describes managed pastures or crops that are grown specifically for those stock – such as fodder maize or whole crop silages – and for the horse it’s grass. Well, more or less.
Before domestication the horse was a stocky animal living on the grasslands of Eurasia, probably on the edge of nutritional deficiency, certainly not able to expend the sort of energy we require of him because he was grazing on poor quality grass, which was only plentiful for half the year. It is thought that conditions such as Cushing’s Disease and IR may be a result of our steam-rollering those natural rhythms of feast and famine and the horse’s hormonal responses to these states!
Now we have bred whole classes of animals from miniatures to shires with different requirements for different lifestyles, from low energy maintenance of the pony in a pasture to the intense expenditure of the racehorse or the sustained expenditure of endurance riding, and all these must be processed by the gut – which has not changed at all! The gut is still designed to process poor quality forage.
Another complication is that while we were improving the shape and musculature of our horses we were also breeding better grasses. But not for horses. These grasses may give us the perfect lawn or help maintain high yielding dairy cows but they are not necessarily ideal for some breeds or levels of activity.
The modern horse may not have access to fresh grass, certainly not 24/7, and grass may not even be the main forage source. In the UK, hay, haylage and bagged forage usually supply the forage portion of the diet, alongside varying amounts of grass. In winter when turnout is restricted and the quality of the grazing decreases, many horse owners introduce a forage replacer to keep bulk fibre levels high for a healthy gut and to meet their inherent needs. At other times of the year, when some horses may need their grass intake restricting (e.g. laminitics), forage replacers can also be used as a ‘low risk’ forage source.
We are increasingly becoming aware of the need to supply fibre as the main source of energy as it has benefits, both physical and physiological, that are not automatically provided by other sources, and the best source of fibre is still forage. It also is the cheapest and so makes sense to optimise its use. Mediating this fibre uptake is becoming the role of the forage replacer/alternative. And this is done in one of three ways;
1) Forage Dilution. Basically for horses who are at the maintenance end of the scale. They may be resting, prone to fat or who have underlying issues that require a low energy diet. Here the replacers are usually built around chaff or straw. We are supplying high levels of cellulose that is broken down only slowly in the hindgut and helps offset the faster fermentation of grass or hay that has greater levels of the more fermentable hemicellulose and soluble fibres. Additionally they are traditionally low in protein and sugars, both of which can reach surprisingly high levels in grass.
2) Forage Extension. Here we are supplying a fibre product that is similar in profile to a reasonable quality hay or grass and is used to even out the variations that are present in the forage, whether it is changes in fibre content and profile, protein or sugars. Here the basic forage is suitably matched to the horse and its lifestyle, all we are doing is ensuring consistency of product and, in extreme cases where our forage runs out, providing a short term alternative to that forage.
3) Forage Enhancement. Forage alone is not sufficient to provide all the nutrients required for the more active horse. People may prefer not to rely too much on traditional hard feeds for a variety of reasons and so choose forage enhancement. These products are based upon super fibres, which really mean sources high in soluble fibres, pectins and hemicelluloses, and low in cellulose and lignified material. Generally speaking these are usually beet pulp, soya hulls and oat fibres, though alfalfa can be another source. By providing highly fermentable fibre sources the daily energy intake of an active horse can be significantly increased without resorting to starchy feeds.
Although there are three distinct areas where forage is “replaced” they all have a common factor. They provide extra fibre without extra starch/sugars and without high levels of protein. Bearing in mind that grass, depending on the time of year, can have on a dry basis up to 25% protein and 30% sugars, diluting these levels with good quality fibre can offset potential nutritional problems of oversupply. Maybe ‘forage replacement’ is not always necessary, but ‘forage management’ certainly is.