Marvellous microbes

Our ace nutritionist – Lisa Elliott MSc – wrote an article for HORSE Magazine on Marvellous Microbes!

Did you know that there are more microbial cells in your horses’ hindgut than tissue cells in their whole body? These gut microbes have a significant impact on your horse as along with fibre fermentation they have valuable and beneficial roles within the body.  However, just as much as they can promote good health, certain types of microbes can also negatively affect your horses’ health and be the cause of disease.

Horse are herbivores and their digestive systems have evolved over many years to consume an almost continuous supply of fibrous feed. This fibre is digested in the hindgut, which represents two major organs – the caecum and colon. As fibre is complex, the horse’s enzymes cannot break it down so instead, it is broken by billions of microbes living in the hindgut through a process known as fermentation.

What are Microbes?

Put simplymicrobes are tiny, microscopic life forms with an enormous influence on all living creatures. Microbes are everywhere, you can’t avoid them and just like horses, our bodies also house billions of them. Microbes are spread throughout the horses’ digestive tract, but the largest numbers by far are present in the hindgut. Hindgut microbes include protozoa and fungi but the largest population in the hindgut are bacteria and it is the bacteria that are predominately involved in fermentation.

Microbial types and function

The hindgut bacteria responsible for fermentation can be divided in to three main functional groups: Cellulolytic (digest fibre), Amylolytic and Glycolytic (digest starch and sugar and produce lactic acid) and lactic acid utilising bacteria.

These diverse types of bacteria live together with other gut microbes in a delicately balanced hindgut community with a mutually beneficial or ‘symbiotic’ relationship within an optimal pH of around 5-7.  Cellulolytic bacteria are the most beneficial to your horse, as these break down fibre into Volatile Fatty Acids (VFA), namely acetate, butyrate and propionate which provide energy. A healthy population of cellulolytic bacteria means improved breakdown of fibre for optimum condition and healthy microbes = a healthy horse.

Gut microbes and health

Your horses’ hindgut microbes have many important roles in digestive health and are vital to promote wellbeing.  All the VFA which are released from the breakdown of fibre, for example, stimulate cell growth and division in the gut membranes helping to strengthen hindgut integrity. Bacteria are also known to synthesise Vitamin K and essential B vitamins such as Biotin.

Research has shown that gut microbes are involved in blood vessel development and help strengthen and stimulate the immune system. The gut microbes are also a critical line of resistance to invading pathogenic or disease-causing microorganisms. This is known as the ‘barrier effect’, and it means that harmful bacteria are competitively excluded, which helps to prevent serious illness and disease.

Whilst a healthy, well-balanced microbe population has huge benefits for your horse, any disturbance to the microbial equilibrium can have the opposite effect and be potentially harmful. Certain situations such as excessive cereal starch reaching the hindgut or sudden dietary changes, for example from hay to lush pasture can result in microbial imbalances or ‘dysbiosis’ which can invariably lead to hindgut acidosis. Hindgut acidosis is a consequence of the rapid growth of certain types of lactic acid producing bacteria. The increased lactic acid causes a drop in pH and results in a more acidic environment and can lead to inflammation of the hindgut membrane and potentially laminitis or colic.

So, to optimise your horses’ digestive health and prevent upset you need to nurture the right microbes through the right diet and feed management.

Feeding for microbial health

The key to achieving the happiest and healthiest hindgut microbes is by feeding plenty of ad-lib, good- quality fibre. Fibre promotes microbial equilibrium and encourages the growth of cellulolytic bacteria and research has shown that horses fed mainly fibre have a more stable microbial community. A more stable microbial community means a healthier horse and a high fibre diet helps nurture this stability.

Making dietary changes gradually will promote good overall microbial health as sudden change is one of the major causes of microbial dysbiosis. Dietary changes include everything like changing from a mix to a cube, changing to a different balancer for example, and fibre based changes such as going from hay in the winter to lush summer grass or even winter to summer grazing. Gradual change means changes should be introduced very slowly, over a period of at least two weeks to allow the gut microbes time to adapt to the new diet, keeping them stable and healthy.

Keeping dietary starch to a minimum benefits hindgut microbe health. If cereals are fed for work then keeping meal sizes small and ensuring they are suitably cooked or processed for improved digestibility will help reduce the chances of starch reaching the hindgut and disturbing the microbial equilibrium.

Pro and pre-biotics

Probiotics are thought to promote microbial health by introducing certain live microbes to improve and support the hindgut microbe population.  Live yeasts (which are actually microscopic fungi) have been shown to stimulate cellulolytic bacteria and increase fibre digestibility but research in horses has proved variable and inconclusive. Live yeast was shown to improve fibre digestion but did little to promote the growth of cellulolytic bacteria with the levels of those bacteria remaining unchanged or sometimes even decreased.  There is also always the question of whether enough live yeast to make an impact can survive the acidic environment of the stomach and reach the hindgut.

Prebiotics work differently to probiotics in that they provide a food source for beneficial bacteria and are therefore, unaffected by stomach acidity.   Yeast based prebiotics can help promote digestive health by providing a feed source for beneficial hindgut bacteria, including cellulolytic bacteria. Yeast based prebiotics are scientifically proven in horses to not only promote optimum fibre digestibility but also to help nurture and stimulate the growth of beneficial bacteria. Feeds which contain yeast based pre-biotics are, therefore, a good way of helping the right hindgut microbes to thrive which in turn should help your horse to thrive too.

Your horses’ hindgut microbes are vital for health, condition and performance. Recognising how feeding can affect these microbes and knowing how you can enhance them through the right nutrition can only be good because the healthier the microbes, the healthier your horse will be.

If you have any questions about creating the best diet for your horse and keeping your horse healthy through the right nutrition, please contact Lisa at – theteam@castlehorsefeeds.com

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