The most difficult and important factor in feeding horses during drought is providing all the roughage they need to maintain a healthy gut.
What is roughage?
The first rule of good horse nutrition is to feed plenty of roughage because the horse’s gut evolved to continuously ingest and digest the fibre contained in roughage.
The bare minimum amount of roughage required by a horse is 1% of it’s bodyweight in DRY MATTER intake. A horse with access to lots of fresh pasture will happily graze for the majority of the day to consume its daily requirement of dry matter. He will also drink less water when grazing lush pasture because the grass has a high water content.
However, under drought conditions, a horse can consume its daily dry matter requirement in the form of hay in a relatively short period of time. This often leads to horses standing around with nothing to eat for hours on end waiting anxiously for the next feed time.
There can be severe mental and physical health impacts on horses denied their daily minimum intake of roughage. Horses’ stomachs secrete acid all the time, unlike human stomachs, which are stimulated to produce acid by chewing.
Acid build up in an empty horse stomach can lead to ulcers, diarrhoea, pain-related bad behaviour and colic. Horses become anxious when left without food, causing them to release stress hormones.
Roughage usually contains at least 18% fibre. The most common forms of roughage fed to horses are pasture, hay or chaff, but there are ‘super fibre’ feeds, such as soy hulls and beet pulp, which are not only fairly high in fibre, but also contain moderate levels of energy.
The best choice of roughage for a drought ration will be very much influenced by price and availability. Ideally, choose hay over chaff or cubes because the long stems encourage more chewing, which creates more saliva to buffer stomach acid and lessen the risk of ulcers. Free choice grass hay is the best replacement for fresh pasture during drought (if you can find any!) and the addition of a kilogram or two of lucerne or cereal hay at meal times provides variety for a better balanced diet.
Try to avoid feeding all lucerne hay because of its very high protein level. These guidelines need to be modified if you are feeding an insulin resistant or laminitic animal as you will need to limit intake to 1.5% of bodyweight for weight loss, choose a low starch/sugar hay and provide a small amount of lucerne or quality protein to aid recovery.
Hay can be fed in multiple piles around the paddock to stimulate more natural grazing (preferably on a mat to prevent sand ingestion), in large round bales offered free choice or in slow feeder haynets to help make the hay last between feed times. The key is to make sure that your horse is NEVER left without something to eat.
What is Dry matter?
Dry matter doesn’t have to be fed dry! It’s just a measure of how much solid matter is in a feed after the water content is removed.
Lush green grass can be 10-20% dry matter or 80-90% water. Dryer, more mature pasture can be 20–30% dry matter or 70-80% water.
Grass hay is typically 90% dry matter or only 10% water. Because 1 kg of lush grass contains less than 200 grams of dry matter, a horse will need to consume more kilograms of lush pasture to obtain the same amount of nutrition as he would get from 1 kg of hay (900 grams of dry matter).
When nutritionists recommend a minimum of roughage, it is always based on the dry matter weight, not the actual weight of the hay - for example, 1 kg of grass hay provides the horse with 900 gms of dry matter.
So, what exactly is fibre?
Fibre is the structural components of plant cells, made of cellulose, hemicellulose, pectin and lignin. The cells in the young, leafy part of a grass plant have relatively thin cell walls but, as the plant ages, it adds strength to the cell walls in the stem to make it strong enough to act as the plant’s skeleton.
Flowering grass plants produce strong stems to carry their flowers, so the fibre content is higher in flowering and seeded plants than in young, leafy plants. Straw is high in lignin to provide a lot of strength to the stem.
Horses cannot digest cellulose, hemicellulose and pectin in the foregut (stomach and small intestine) because they cannot produce enzymes able to break down these very tough fibre components. Digestion of these fibres relies on the beneficial microorganisms in the hindgut (mainly the cecum) that are able to break them down into volatile fatty acids for digestion.
These little guys are the main reason we need to adjust horse diets gradually - when there is a sudden change in diet, the whole population needs to change to help digest the feed, but it takes time to breed up enough of the new ones. Lignin cannot be digested by horses or by the bacteria in their hindgut, making straw an unwise choice to feed your horse.
Designing a drought ration for your horse
Many horses do not get enough roughage in their diet, especially during drought. Easy keepers and horses at rest or in light work may be able to get all the energy and protein they need to be healthy from roughage alone. Hard working horses or those harder to keep weight on need more energy than roughage alone provides.
As a good rule of thumb, horses need to consume between 1.5% and 2.5% of their bodyweight in feed per day (that’s the feed’s dry matter content, not counting the moisture present). The absolute minimum amount of roughage fed recommended by nutritionists is 1.25% of bodyweight.
A horse at rest should consume 80-100% of its daily intake as roughage. Horses in light work may need 65% and those in moderate work need 55-65% of their diet in the form of roughage.
Horses undergoing intense training may only have enough capacity to consume 40-50% of their daily intake as roughage due to their high consumption of energy feeds (grains/oil).
Pregnant, lactating and growing horses may also need a protein supplement to provide the necessary levels of essential amino acids, especially lysine, methionine and threonine.
Once the drought diet has met the daily requirements for roughage, energy and protein, vitamins, minerals and salt need to be added to fill gaps and balance the critical mineral ratios to create a perfectly healthy diet. The vitamin levels in hay decline rapidly with storage and year old hay has virtually no vitamins left, although it will retain the minerals it had when harvested.
Pellets and fortified mixed grain feeds usually contain added salt, but a horse fed roughage alone or a straight grain for energy will need extra electrolytes. Free choice salt is advisable and a minimum of 20 g plain table salt per day is a guide for an average sized horse.