"As the cold winter nights draw in and the temperature falls, pasture stops growing and eventually, if cold enough, becomes dormant.
"This pasture may look green and plentiful but actually contains indigestible woody fibre and fewer vitamins with a much-reduced feed value.
"This also means that the horse's energy intake from pasture falls and it can consequently lose weight quickly as more dietary energy is needed just to maintain body temperature," she added.
Energy intake is recognised as the most critical in determining how readily a horse develops a tolerance for the cold.
Horses lose weight if they do not absorb enough energy to offset the heat loss to the cold, surrounding air, so enough feed and good-quality nutrition are needed to supply an adequate energy intake for the horse.
Fat horses are able to mobilise some of their fat deposits as energy during cold snaps, but enough good feed is the main solution for keeping horses in good condition through the winter.
Well-fed horses adapt without problems to cold weather, whereas unfed horses lose weight and therefore a tolerance to the cold. In fact, studies have shown that yearlings fed a high quality diet, ad-lib, are able to tolerate temperatures as low as -11 C with no ill effect.
Horses will generally eat to meet their energy requirements. In cold weather, feeding good-quality hay, ad-lib, is the simplest way to ensure that the horse meets its energy requirements.
"In general, it is a good idea to plan ahead and begin offering smaller quantities of hard feed and conserved forage such as hay or haylage in late autumn, so that the digestive system adapts, minimising the risk of digestive upsets and colic," Ms Davies said.
When they are given free access to hay, most horses will eat around 2-2.5pc of their body weight in hay a day.
However, winter pasture, hay and haylage can lack amino acids, minerals and particularly vitamins that are necessary for an animal's health, so some additional concentrate feeding may be required.
Individual animals may also need additional feeding, such as older horses, youngsters, in-foal mares, 'bad doers' and other stock whose condition is less than optimum.
According to Ms Davies, the choice of hard feeds will depend upon factors such as:
- Condition of the horse or pony;
- Age -- stage of breeding cycle or veteran horses and ponies.
"If more calories are required, a higher energy compound feed and/or oil may be fed," Ms Davies said.
"This includes underweight horses and ponies, breeding stock and working horses, which will need additional higher energy hard feed or concentrates to help them gain or maintain condition."
Referring to specific products from Gain Feeds, Ms Davies said horses and ponies in optimum condition going into winter could be fed the Gain Cool 'n' Easy mix or, if a lower starch feed was preferred, Gain Easy Go cubes.
"If horses and ponies need more condition and more energy is needed, the next step up would be Gain Hi Grade Horse and Pony cubes," she said.
The company also produces stud cubes and coarse mix for broodmares.
"The choice for very good doers and overweight types, would be a low calorie balancer such as Opti-Gro, which will provide the vitamins and minerals required over winter," she added.
Owners need to ensure that fresh water is always available to horses, especially since hay, haylage and concentrates all contain less water than fresh grass, so horses in the winter months will need to drink more.
One of the biggest dangers of not having adequate water available is that the horse could develop impaction colic.
It is also important to remember that as water temperatures fall, horses drink less and so, if possible, hot water should be added to take the chill off drinking water in cold spells.
A salt block is important as forage can be low in salt -- and this should be made freely available if more salt is required, she added.
Managing groups of horses at grass can be quite a challenge because grouped horses typically have a pecking order for feed and space. Often, timid horses will become thin, even if plenty of feed is available, because the dominant horses in the group won't allow them to eat.
To ensure that each horse has access to enough hay, owners can set out more piles of hay than there are horses, ensuring there will always be a spare pile for a horse that is bullied away from its first pile. Generally, there should be 3-15m between each horse to minimise bullying.
When feeding concentrates, feeding should be supervised so that each horse gets to finish its feed uninterrupted.
Shelter is a critical factor in determining how much additional feeding a horse will require.
Studies have shown that horses with access to a shelter or shed can conserve up to 20pc more body heat than horses kept in an exposed area.
Where horses have free access to a shelter, it should be a three-sided shed so that a horse can escape from another aggressive horse if needs be. A typical shed should be 8m deep, with 7.5-9m2 for horses to lie down as animals that are able to do this can reduce surface area heat loss by 20-25pc.
Adequate bedding should be provided in sheds, especially for young horses.
In some instances, a well-sheltered area within the field can be an effective alternative to a man-made shelter.
Another critical factor to consider when trying to maintain a horse's bodyweight during the winter months is whether the horse should be rugged. While a native breed with a good, woolly winter coat might not need a rug, a thin-skinned thoroughbred could do with some help from a suitable outdoor rug.
Finally, routine healthcare such as worming and care of the feet and teeth must also be addressed throughout the winter.