As we no doubt all know, the modern horse developed on the open plains of the northern hemisphere, where the predominant ground vegetation is grass. And here in the U.K. we have a huge resource of grass. And horses eat grass, right? And at least some of our horse’s diet consists of hay or haylage, from grass.
Grass comes in many types, varies tremendously through the growing year and suffers nutritionally during preservation, depending on many factors. But the reason it is so important to the horse is down to the range of nutrients it provides. Notwithstanding protein, oil and micronutrients such as vitamins and minerals, the main bulk of grass is fibre and the horse has evolved alongside this fibre source so it has the capacity to ferment it in the hindgut releasing nutrients for energy.
So what happens in countries that do not have sufficient grass to give hay/haylage, or countries where drought can have a devastating effect on grass production? How do they cope?
We are increasingly finding out more about the environment in the horse’s gut – especially the hindgut and how the microbes interact and alter to changes in diet. From this our understanding of fibre fermentation can help us determine the best dietary composition for different lifestyles. The main components of fibre fermentation used for energy by the horse, are Acetic (A), propionic (P) and butyric (B) acids (the VFA). For example cellulose, which is fibre that makes plants rigid, ferments in the hindgut to produce mainly acetic acid, whilst grass/hay produce the VFA in the ratio of 80:15:5 APB.
Of these components each has a slightly different metabolic function; acetate provides base line energy. Propionate can be metabolised to glucose – providing important energy source for the brain, fast twitch muscles and areas of poor oxygen supply, and butyrate is used to maintain the energy of the gut wall itself.
So the main nutritional purpose of fibre is to provide energy, in proportions we believe to be the best for the horse. Luckily for us in the UK this is probably grass, or at least it is close enough for us to manipulate with other fibre sources, such as Speedi-Beet to increase the overall energy supply.
So, understanding fibre properties means we can provide the right proportions either by supplementing grass or, in other circumstances, replacing with sustainable alternatives. In South Africa, for example, oat hay and alfalfa mixes can be used to supplement kikuyu grass, and Australia soya hulls are becoming popular.
Fibre is made up of many different types and combinations of beta-linked carbohydrates and so can be combined to give a fibre profile, or a fermentation pattern, that best benefits the horse. For example Fibre-Beet a combination of alfalfa, beet and oat fibre, has a profile that is very similar to grass, whilst Speedi-Beet has a fermentation pattern that provides extra P and B, thereby supplying more energy from a similar profile.
There are many fibre mixes and hay alternatives out there, based on any number of fibre sources – wheat or oat bran, straw, chaff, beet pulp etc. – and so there are plenty of alternatives, on paper, to hay/haylage. But look at the ingredients; keeping starch levels low will help ensure proper hindgut function and therefore optimal use of hindgut function allowing you to use a range of alternatives to hay/haylage.