Feed the Need: How much should you feed for effective weight management?

By Equine Science and Nutrition Specialist Professor Meriel Moore Colyer

In this article equine nutrition specialist Meriel Moore Colyer explains the importance of maintaining optimum body condition throughout the year and what we can do to achieve it.

"Following her popular evidence-based presentation at the Horses Inside Out Conference earlier this year, we are delighted that Meriel has agreed to present a series of webinars in January and February 2025."

Gillian Higgins

Prof Meriel Moore Colyer is a research scientist focussing on Equine Nutrition

One of the challenges all horse owners face is keeping our horses in optimum body condition throughout the year. I think this is particularly challenging in the UK as we don’t have a climate, but just experience weather! Therefore, predicting  the nutrient content in grass and forage based on the time of year is impossible, as sun, rain, soil nutrient content and physiological age of the plant all have major impacts on nutrient content. 

We then have the other variable to deal with, and that is the horse itself. Horses, are much more individualistic in terms of their gut microbiome than farm animals, so what suits 1 horse might not suit the other, despite the fact that they may share environment, exercise regime and feed sources. Scientific research on the equid microbiome has revealed that the microbial profile in the gut has major impacts on gut health, orthopedic health, respiratory health (Pollitt, 2023), immune health and behavioral characteristics (Mach,2020). So it’s important to feed to maintain as healthy a microbiome as possible. 

Research on the human gut microbiome has shown that people who are overweight have a different microbiome profile to those who are slim and similar findings were noted in horses by Morrison et al (2020).  

Furthermore other gut characteristics such as the rate of passage of food through the digestive tract is also highly individual (Moore-Colyer et al. 2003) and will impact the efficiency of digestion and fermentation and therefore how much ‘value’ a horse obtains from its diet.

With all these variables it is not surprising we struggle with achieving and maintaining ideal body weight, optimum health and performance. 

Meriel will be presenting Nutrition Nurtures Everything in January and February 2025. In this series of 4 webinars, Meriel will explore how feeding underpins optimum performance of all your horses’ body systems. From gut physiology to choosing the right supplement for your horse, this series of seminars will put science into practice in an easy to understand way and give you the tools you need to improve the most important every-day activity of feeding your horse.

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So what can we do to help our horses stay in optimum condition? 

Understanding the physiology of the gut and how feed can impact the microbiome, rate of passage, water absorption and nutrients gained from the diet is the first step. This webinar will examine the most important aspect of gut function that will influence what you feed. Eg feeding fibre (grass, forage, soya hulls sugar beet pulp – yes the latter 2 are fibre feeds!) will speed up the passage of food through the digestive tract. If you have a horse prone to impaction colic then this is a good thing. If however, you are feeding some cereals for extra energy, then speeding up the passage of this through the small intestine can lead to incomplete enzymatic digestion and dumping of highly degradable material into the caecum, which can lead to digestive upset, colic and even laminitis. So while we all recognise that horses should have continuous access to fibre, it would be best to feed the cereals then wait an hour before giving the forage / turning out onto pasture. This gives the small intestine time to really digest the starch, protein and fat, preventing dumping into the caecum.  In the webinar we will examine how the different regions of the gut influence digestion and how an optimum diet for each horse can maximize the functioning of each section and thus promote health in our horses. 

Many people, and some vets, will say that the equid digestive system is ‘ a Friday afternoon design’!! Well don’t you believe it, the gut has evolved to efficiently deal with a range of fibre feeds but its structure means that the way they carry fibre in the gut does not impact the animal’s ability to run fast. Cows cannot run fast because they have a huge fermentation vat, the rumen, which is so heavy that it prevents them from running (unless of course you are chasing them across a field!!). Horses  have evolved to thrive on the same food as cows but horses can gallop, very fast, so that in my book that makes the horse a much superior herbivore, and a ‘Monday morning’ creation!

My career as an equine nutritionist has always been led by research and I try to share the practical aspect of my work with horse owners to help them improve ration formulation. One such study, prompted by the rise in obesity of our horse population, involved re-evaluating the energy requirements of horses using animals in their normal environments and undergoing normal training. My PhD student Mark Ebert measured energy utilisation in 60 performance horses (Ebert and Moore-Colyer, 2020) and has devised an easy to use equation which allows you to determine the likely energy requirements of your horse. This is the most accurate method for guiding your determination of energy requirements. As I’ve mentioned above every horse is an individual so the basic calculation may need some ‘tweaking’ but using this equation will be an excellent starting point and  avoids the thorny issue of deciding if your horse is in hard, medium or light work. 

Maintenance, i.e., keeping body and soul together and maintaining a healthy body weight uses the biggest proportion of the dietary energy. So we have to calculate Energy Expenditure for Maintenance (EEM) first. This is an easy, but several-step process detailed below. 

You need to know the body weight (BW) of your horse, and if you can obtain this accurately using a weigh-bridge then that is a great start. Then put the weight in Kg into the following equation:

EEM (in MJ of ME / day)  = BW x 0.118

Then the amount of energy required for exercise (EEE) needs to be added. Mark discovered that even horses doing horse trials and advanced dressage did not require any more than an additional 15% of their EEM. So take the value you have calculated for EEM and multiply by 15%  i.e.

EEE (MJ ME/day) =  EEM x 0.15

You then add these 2 values together:

Total energy requirements / day  (TERD) = EEM + EEE

And to make matching this with feed contents and values on feed bags easy, we convert the ME to DE so:

Take TERD value and calculate what 20% of that is. i.e.  TERD x 0.2 Then add this to the TERD value = Full dietary requirements in MJ DE / day 

So give this a try and we can discuss it at the webinar. It is an easy-to-do 4 step process and you will find it re-sets the amount you are feeding. This is particularly relevant for today’s UK horse population, as obesity is on the rise and we all need to re-evaluate what we are feeding. This will give you confidence that you are feeding the correct amount and reduce the temptation to add the ‘little extra’ which causes un-wanted weight gain.  

There are a vast range of feeds to choose from on the market, and often it is difficult to decide which would be best for your horse. Part 2 of this webinar will examine feed characteristics, and how you mix and match different feeds. I approach this from a fundamental feed composition angle which should allow you to asses the suitability of any compound feed on the market . Learning this will help ‘future-proof’ your knowledge so you will be able to assess any feed, even those not yet on the market, for suitability for all your horses.  

So join me on the ‘Feed the need’ webinar on Wednesday 29th January for the first in the Nutrition Nurtures Everything series and learn more about the most important system in your horse’s body!

Meriel Moore-Colyer 

Feed the Need – Webinar 1: Wednesday 29th January 2025

In this webinar Meriel will consider the important relationship between form and function by examining gut physiology and how that influences digestion, absorption and diet choices. Feeding is a daily activity done by all horses owners so this webinar will have useful and applicable information whether you are feeding a week-end ridden leisure horse or a top-class performance horse. By applying science to practice the latest information on the equid gut microbiome and assessing energy requirements of your horse will be covered. Balancing the major dietary ingredients will complete this topical course. 

Timetable:

18.00: Webinar Opens

18.30: Welcome and Introduction

18.45: Part 1 - The Triangle of Life

Gut capacity

Rate of passage

Microbiome health

Scientific ration formulation as a guide

Weight assessment

19.30: Break

20.00: Part 2 – Fixing the Feeding

Balancing the diet

Fibre feeds

Cereal feeds

Fat

Supplements 

20.45: Q&A Session

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References

Philippa K. Morrison, Charles J. Newbold, Eleanor Jones, Hilary J. Worgan, Dai H. Grove-White, Alexandra H. Dugdale, Clare Barfoot, Patricia A. Harris, and Caroline McGregor Argo. The equine gastrointestinal microbiome: impacts of weight-loss. BMC Vet Res. 2020; 16: 78. doi: 10.1186/s12917-020-02295-6

Mark Ebert, Meriel J S Moore-Colyer (2020).  The energy requirements of performance horses in training Translational Animal Science, Volume 4, Issue 2, April 2020, txaa032. https://doi.org/10.1093/tas/txaa032

Moore-Colyer, M.J.S.; Morrow, H.J. and Longland, A.C. (2003) Mathematical modelling of digesta passage rate, mean retention time and in vivo apparent digestibility of two different lengths of hay and big bale grass silage in ponies. British Journal of Nutrition. 90: 109-118. (DOI 10.1079/BJN2003869)

Mach N. Alice Ruet, Allison Clark, David Bars-Cortina, Yuliaxis Ramayo-Caldas, Elisa Crisci, Samuel Pennarun, Sophie Dhorne-Pollet, Aline Foury, Marie-Pierre Moisan & Léa Lansade. Priming for welfare: gut microbiota is associated with equitation conditions and behavior in horse athletes Scientific Reports. 2020. https://doi.org/10.1038/s41598-020-65444-9

Chris Proudman (2023) Results of a cohort study of foals from birth to 3 years old: microbiome, immune status and health outcomes. Proceedings of EEHNC Ghent Belgium, 11th Edition 39-40