Feeding horses during the winter months can be challenging. For the last few years, our UK winters have been mild and wet, but this year, temperatures have dropped for a consistent period and in many parts of the UK, there is little or no nutrition left in the grass. For those horses kept at grass full-time and for those turned out for periods of the day, therefore, their grazing now needs supplementing with alternative forms of forage.
‘Forage’ (or ‘fibre’, such as grass, hay or haylage) should form the basis of any horse’s ration. In their natural environment, a horse would spend approximately 18 hours a day foraging, rarely fasting for more than 2 – 4 hours at a time. Saliva is generated in response to chewing and this helps to buffer gastric acid, which is secreted continuously into the stomach. In addition, natural living conditions encourage the horse to move freely, which is believed to assist with the normal movement of stomach contents through the gastrointestinal tract.
Ensuring suitable levels of forage intake is therefore essential for the health of an equine’s gastro-intestinal tract, but equally important, forage plays a thermoregulatory and nutritional role for the horse. Horses are ‘endothermic’, meaning they can produce heat through metabolic processes in their body, enabling them to maintain their average body temperature (Frappell et al., 2008).
Thermoregulation – Heat Increment
Metabolic processes, including heat provided from nutrient metabolisation, maintain an equine’s body temperature.
The equine gastro-intestinal tract is unique, in that enzymatic digestion occurs in the foregut, whilst fermentation occurs in the hindgut. The equine hindgut is resident to a vast population of microbes or microbial population, that break down, or ferment, fibre-based feeds. This fibre is converted into ‘volatile fatty acids’, which are then absorbed and utilised by the horse’s body. As a by-product of fermentation, metabolic heat is generated – helping the horse stay warm from the inside out and supporting thermal comfort. (Santos et al., 2011) It is worth noting that feeds that are high in grain (starch), on the other hand, are ultimately, the reverse of forage and do not produce metabolic heat as a by-product (Merritt et al. 2013). We refer to this as ‘heat increment’ and fibre-based feeds have a higher heat increment than low-fibre feeds, such as grain. (Julliand et al. 2004)
Current recommendations are to feed approximately 2 - 2.5% of the horse’s current bodyweight (BW) in forage per day. (Maintenance diets should involve around 2% of a horse’s BW per day, whereas older or growing horses should consume 2.5% of their BW on a daily basis). As an absolute minimum, it is recommended to provide at least 1.5% bodyweight per day.
Good quality forage contains a number of nutrients and may be capable of providing enough Digestible Energy (DE) for healthy horses in maintenance or light work. It is also worth noting that fibre provides slow-release energy (Hervik et al. 2019), so can be ideal for horses that can become over-excited.
Harper et al. (2004) estimated an increase of 10-15% good quality forage to be fed when temperatures drop below freezing level (0℃). Ideally, an unlimited (ad libitum) supply of forage fed at ground level is the best way to meet a horse's behavioural and nutritional requirements during winter when there is an increased demand for heat production. Nevertheless, this system may not be appropriate for all horses. For example, an overweight horse would benefit from a restricted intake due to weight loss; so, in this case, their daily requirement intake can be spread out throughout the day with lower digestible energy fibre feeds being provided, such as soaked hay.
On the other hand, for young, old, thin, or performance horses who are more vulnerable to winter temperatures, or have a high energy output due to exercise, forage alone (although it should always form the foundation of their diet), may not be sufficient to keep them in top condition, as they cannot consume enough forage to meet their daily digestible energy requirements. Additional calories are therefore, required and can be provided through a range of different feeds. Highly digestible fibre-based feeds, such as beet pulp, are a good starting point.
Beet Pulp contains high levels of soluble fibre, including pectins, which are highly fermentable - thus, it is termed, a ‘highly digestible fibre’ or even, a ‘superfibre’ - as the dry matter digestibility is approximately 80%. (Hyslop, et al., 1998) It is also higher in digestible energy than traditional fibre feeds, such as hay. In fact, the digestible energy levels in unmolassed beet pulp are similar to a medium-energy concentrate feed, yet the starch levels are much lower.
Older horses, particularly those with poor teeth, can struggle in the winter and lose condition dramatically. Again, beet pulp or fibre cubes soaked into a mash, are a good addition or alternative to forage, when chewing becomes difficult.
However, it is important to remember that it is natural for equines to lose some weight in the winter months and fundamentally, owners should not get worried about a small amount of controlled, weight loss. Indeed, winter is the easiest time to manage horses and ponies that are overweight or obese, and owners should be using winter to their advantage to increase weight loss.
Overall, a winter-feeding programme should be based on pasture availability and good-quality forage, supplemented with appropriate sources of digestible energy, protein, vitamins, and minerals. A diet high in fibre should meet the increased heat demands for an equine during winter, whereas low fibre diets would not fully support metabolic heat increment requirements.
As crucial as forage consumption is during the winter months, water intake is equally important. Horses lose water from their body through faeces, urine, sweat and even through exhaling air, as dry cold air increases water loss from the respiratory tract and lungs. On top of this, forage consumption in winter increases resulting in extra water being required for fibre metabolisation in the hindgut.
The accepted water requirement for horses is around 60ml/kg/day (Freeman, 2021). Thus, an average 500 kg horse requires approximately 30L of water per day as a minimum requirement. In addition, summer grass has moisture levels of approximately 60-80%, contributing to the horse’s water intake. In contrast, in winter, hay (and concentrate feeds) are fed more abundantly and these contain less than 15% moisture and so, do not contribute as highly to the horse’s daily water intake (Cymbaluk, 2013). Water is necessary for maintaining moisture levels in the horse’s gastrointestinal system therefore decreased water consumption causes ingesta to dry up, increasing the risk of impaction colic or intestinal blockages. (Bihonegn, 2018)
Kristula et al. (1994) performed a study consisting of two trials to compare ab libitum consumption of ambient near-freezing water (ranging from 0℃ to 1℃) and warm water (46℃ to 49℃ when provided) to 14 ponies. The study concluded that on average, 40% of the ponies drank more warm water compared to ambient, near-freezing water. Based on this study, providing warm water for horses may encourage them to drink and help maintain hydration levels. Another factor to consider, is that low temperatures encourage water to freeze, therefore through correct management water troughs / buckets should be checked at least twice a day to break and remove any ice, if the water supply has frozen. (Supplying warm water may minimise this risk, although this may not be practical for many owners).
Vitamins and Minerals
As forage is consumed in greater quantities in the winter months, it is a good idea to have winter grass, hay or haylage tested in order to determine the levels of all the vitamins and minerals needed to balance a horse’s daily ration. These minerals are:- calcium, phosphorous, magnesium, sodium, potassium, chloride, iron, copper, zinc, manganese, selenium and iodine.
In winter, a sodium deficiency for example, can impact the amount of water an equine drinks, and when temperatures drop, then horses often drink less anyway. If a horse already has a low consumption of water, then such cold weather behaviour can lead to slow gut mobility and the possibility of an impaction colic.
If forage analysis is not possible, then is recommended to ensure that an equine is receiving the correct quantity of vitamins and minerals by feeding a balancer in their ration, or a straight vitamin and mineral supplement.
A Balanced winter ration
So, to summarise, a balanced winter ration will provide an equine with suitable amounts of digestible energy (DE), protein, fibre and vitamins and minerals, together with adequate water levels. Fibre-based feeds should always form the basis of any ration, and are especially important in the winter for ensuring a healthy hindgut environment, thermoregulation and the correct nutrient levels. Certain horses will need their calorie intake supplemented with additional soluble-fibre based or concentrate feeds.
Finally, always try to keep a horse’s ration simple. Most horses (even those in high levels of competition) will well on an ad-lib forage diet, plus additional concentrate feeds containing chaff, soluble fibre-based feeds (such as beet pulp), possibly some additional high-calorie oil-based feeds, such as micronised linseed meal; and finally, the correct level of vitamins and minerals.
Bihonegn, T., & Bekele, F. (2018). Colic in Equine: A Review Article. International Journal of Advanced Research in Biological Sciences (IJARBS), 5(5):185-192. Christopherson, R. J., & Young, B. A. (1986). Effect of cold environments on domestic animals. In: Grazing Research at Northern Latitudes, ed. 0. Gudmundsson. Nato AS1 Series, pp. 247-257. Plenum Press, New York. Cymbaluk, N. (2013). Water. In: Geor, R.J., Harris, P.A., & Coenen, M. (eds.). Equine Applied and Clinical Nutrition. Saunders Elsevier: China. Freeman, D. (2021). Effect of Feed Intake on Water Consumption in Horses: Relevance to Maintenance Fluid Therapy. Frontiers in Veterinary Science, 8: 1-7. Guthrie, A.J., & Lund, R.J. (1998). Thermoregulation. Base mechanisms and hyperthermia. Veterinary Clinics of North America: Equine Practice, 14: 45-59. Harper, F. (2004). Winter Horse Feeding. Extension Horse Specialist Department of Animal Science, 23(1). Hervik, A.K, & Svihus, B. (2019). The Role of Fibre in Energy Balance. Journal of Nutrition and Metabolism, Volume 2019: Article ID 4983657. Hyslop, J.J., Stefansdottir, G.J., McLean, B.M.L., et al., 1999. In situ incubation sequence and its effect on degradation of food components when measured in the caecum of ponies. Animal Science 69: 147 – 156. Julliand, V., & Martin-Rosset, W. (2004). Nutrition of the performance horse. Wageningen Academic Publishers: Netherlands. Kristula, M., & McDonnell, S. (1994). Drinking water temperature affects consumption of water during cold weather in ponies. Applied Animal Behaviour Science, 41(3-4): 155-160. Lindberg, J. E. (2013). Feedstuffs for horses. In: Geor, R.J., Harris, P.A., & Coenen, M., (Eds.). Equine Applied and Clinical Nutrition, Saunders Elsevier: China. Martin-Rosset, W., & Tisserand, J-L. (2015). Horse maintained outside - Critical Temperatures. In: Martin- Merritt A.M., & Julliand V. (2013). Gastrointestinal physiology. In: Geor, R.J., Harris, P.A., & Coenen, M., (eds.). Equine Applied and Clinical Nutrition, Saunders Elsevier: China. Santos, A., Rodrigues, M., Bessa, R., Ferreira, L., & Martin-Rosset, W. (2011). Understanding the equine cecum-colon ecosystem: current knowledge and future perspectives. Animal, 5(1): 48-56.