Winter is here, and our horses will need more feeding and care to ensure they maintain their body condition in the cold, wet weather. Once the ambient temperature gets below 10°C, grass stops growing, and winter pasture is lower in nutrients as a result. Fewer daylight hours and a weaker sun will reduce the nutritional content of the grass, as photosynthesis (the way the plant produces energy and nutrients) is lessened.
However, not all grass species are the same, and some are more robust in cold and wet conditions than others, which is important regarding how muddy paddocks get.
Horse owners REALLY hate the mud in winter – so think about sowing deep-rooted grasses, which help drainage and hold together the structure of the soil.
In late autumn and winter, most grasses will have more fibre in them, as the carbohydrate generated from photosynthesis will have been transformed from sugar into structural compounds, and the grass may lose its green colour, and hence its vitamin levels (eg. vitamin E). This means that winter grass contains roughly 20% less energy, and reduced protein, vitamin and mineral levels; calcium, for example, may be reduced by 25%.
However, some nutrients, such as copper, can become more concentrated in grasses during winter (Grace et al., 2002).
As a result, hard feeding or supplements, such as vitamin and mineral blocks, are important to keep your horse in good condition, especially if he or she is in hard work, such as hunting.
Water remains the number-one nutrient for all living things, and, just because it is colder, does not make this any less important for horses. In cold snaps, always check water troughs, dams and containers and break the ice to give the animals access. Water should be clean, and, in warm winters and northern parts of the country, keep a check for toxic algae growth.
How cold is cold for horses?
Fibre from forages and the metabolism of other feed materials is important in keeping your horse warm, from the internal heat generated during hind gut fermentation. However, compared to ruminants such as cows which have much more fermentation activity, horses produce relatively less heat, and so are more cold-sensitive.
Research from the combined data from three trials shows that horses ‘lower critical temperature’, ie. the environmental conditions when more internal heat from either fermentation or metabolism of nutrients is needed maintain body core temperature, is around 5°C (Morgan, 1998).
Below this, the horse will lose weight and condition, as it will mobilise body reserves of fat, initially, and then protein in more extreme situations, to keep essential internal processes going.
Some breeds, such as native ponies, are hardier than others, and individuals grow varying thicknesses of coat in winter weather, and this should be taken into account when considering cold stress factors.
Conversely, hot-blooded breeds, such as Arabs and thoroughbreds, tend to be more cold-sensitive and have thinner winter coats. It is not just the external temperature that is important, and in wet or windy conditions, chill factors must be taken into consideration as well.
To prevent loss in body condition, extra feed and shelter, by using suitable covers, and putting the horse in a paddock surrounded by hedging or trees or provided with a field shelter, will be required. The minimum of a waterproof cover in bad weather is important to prevent chilling.
Clipped horses, of course, need heavier covers to keep them warm. Do be careful not to over-rug on warmer days, as this will make the horse sweat, which will result in losses of important minerals and heat stress, the latter which can cause major physiological problems.
Keeping an eye on things
Monitoring your horse’s condition score is important at all times of the year, but especially so during winter, when weight loss can be rapid.
As many horses are covered in New Zealand in cold weather, it is not always apparent that body changes are occurring, so, at least once a week, take off their covers and check they are still in good condition. This means that you should be able to feel the ribs when running your hand over their side with moderate pressure, but not see their ribs. When viewed from the tail, their rump should be level, with no muscle losses or poverty line evident.
In hairier individuals, the visibility of ribs can be more challenging! If you’re unsure about weight changes, take picture once a week on your phone to compare directly.
Which winter forage?
Any forage used to feed horses should be made from good quality, fertilised pasture that is weed-controlled (especially for toxic weeds such as ragwort).
Bales should not be dusty or have any fungal growth. Dust can lead to respiratory problems, especially when fed indoors, and horses are very sensitive to fungal toxins, compared to other species.
Hay is the most commonly used forage for horses, although other forms are useful and can have more nutritional value. The drying processes for making hay reduce its protein and vitamin levels, especially over time. Typical energy levels in hay are 7-9 MJ/kg and 10% protein on a dry matter basis, and hay is around 85% dry matter/15% water.
Silage for horses must be made as long-cut baleage, as short chop, cow silage can easily cause intestinal blockages and colic. This is because the horse lacks a large rumen at the front end of its digestive tract. Its stomach is relatively small, and its intestines are much more convoluted, making it more vulnerable to obstructions. Ideally, use a gas-exchange bale wrap and a probiotic inoculant to get the best fermentation and quality of the final feed.
This form of forage, as it is fermented akin to pickling, preserves more nutrients, especially protein and vitamins. Baleage has a typical energy level of 10-11 MJ/kg on a dry matter basis but contains a lot more water (50-60%), so the amount needed to fed per day will be higher.
Many horses, and especially those with poorer teeth, prefer soft, moist baleage to hay, as it is easier to consume, and is very palatable. The higher level of water in baleage contributes significantly to intestinal hydration, which is very useful for trekking and hunting horses, which are at higher risk of dehydration colic.
The overall nutrient levels in forage is dictated by the quality of the original pasture and when it was cut, and don’t be afraid to ask sellers about the provenance of the forage. In other countries, professional forage suppliers typically give buyers an analysis and some kind of guarantee that it is free of toxic weeds and fungus – this system would be good to establish in New Zealand.
Compound feeds and supplements
Compound or hard feeds that are fully balanced in nutrients should be selected depending on work load, and whether your horse is a good or poor doer.
Balancers are available that are based on fibre, and compliment the lower nutrient levels in pasture during winter. These are especially useful in horses who tend to be fat, or if you have ample good quality forage to feed out.
If your horses are not in work and are good doers, consider using a vitamin and mineral block or bucket in the paddock to top up essential nutrients. It is possible to ward off mud fever by the appropriate consumption of minerals are important for skin integrity, such as copper and zinc. However, you need to feed minerals in a balanced manner, as overfeeding one or two can reduce the animal’s capacity to absorb the others that are required.
The basic rules for feeding in the winter are:
- Fresh, clean water must be freely available
- Provide good quality forage intakes to promote heat generation from hind gut fermentation
- Top up with balanced, complete diets to meet workload requirements
- Provide appropriate covers or shelter in cold weather, taking into account any chill factors, whilst not over-rugging
- Ensure sufficient vitamins and minerals are provided to limit problems relating to skin conditions, such as mud fever
- Check body condition scores on at least a weekly basis, monitor any changes and adjust feeding regime accordingly.
- This article was first published in the June-July 2018 issue of NZ Horse & Pony. Latest issue out now where all great magazines are sold.