How does the addition of yeast contribute to a healthy digestive system?

Horses are hindgut fermenters and have evolved to spend the majority of their day grazing. They produce digestive enzymes to break down certain nutrients, such as fats, protein and simple carbohydrates, but they do not produce enzymes to break down fibre, so they hugely depend on the beneficial microflora that can be found throughout their hindgut. These microflorae are responsible for the fermentation of all the fibre ingested which produces a continually releasing energy source for the horse.

Cellulolytic (fibre-digesting) bacteria make up the majority of the bacterial population in the caecum and colon (hindgut). These bacteria are responsible for the breakdown of fibre and they manufacture B-vitamins. They thrive best at a near neutral pH (approximately 6.8) so they can be particularly sensitive to sudden drops in pH. 

Amylolytic (starch digesting) bacteria are involved in the breakdown of starch and rapidly fermentable carbohydrates. They produce lactic acid and if they grow in number, can significantly reduce the hindgut pH. A lack of fibre, excessive intakes of sugar and starch, sudden changes in diet, stress, sickness along with worming and antibiotics, can all contribute to an acidic hindgut environment. Hindgut acidity can lead to issues such as colic, laminitis, ‘tying-up’ etc.

When the Amylolytic bacteria multiply, the Cellulolytic bacteria die allowing the Amylolytic population to flourish. Live yeast will compete with these organisms for sugar which will reduce their growth. As a result, feeding live yeast will help stimulate the growth of the Cellulolytic bacteria leading to healthy fermentation.

It is preferable to use pure, protected yeasts, which can survive the process of pelleting and the acidity within the stomach, to reach the hindgut where their action is required. Yeasts enhance the activity of cellulolytic bacteria in the hindgut and therefore allow improved utilisation of a horse’s diet. Their mode of action is to scavenge oxygen, maintaining an anaerobic hindgut environment which supports the normal microbial balance.

Feeding horses yeast can improve their overall fibre digestibility by up to 20%. This simply means that a horse will be able to get more energy from the fibre he eats. If the fibre in the horse’s diet supplies more energy, less concentrates can be fed, which is beneficial for both health and behaviour.

Yeast also contributes to maintaining hindgut health during times when horses become stressed e.g. travelling to shows, moving to a new yard etc. These horses may suffer from loose droppings and come back from a show tucked-up. Yeast can help prevent this as it also has a calming effect on a lot of horses.

For more information contact the Equerry Nutrition Team on 01845 565640 for an individually tailored feeding plan.