Feeding Horses in Times of Drought

Dr Glenys Noble PhD, GradDipMgt, GradCertUnivTeach&Learn, BAppSc(Equine Studies), Senior Lecturer Equine Science, Charles Sturt University, Wagga Wagga NSW.

One of the biggest challenges faced when feeding horses in drought conditions is ensuring they get enough dry matter.  Equine nutrition is often preoccupied with the provision of energy, protein, minerals and vitamins, meaning that dry matter, which is a critically important component of the ration, is often overlooked.  Dry matter is what you are left with if all the water was extracted and is therefore the actual amount of feed the horse eats. The dry matter of a feedstuff is worked out in a laboratory by drying it out in an oven for about 48 hours.  Any information you receive about the nutrient composition of a feed is worked out on a dry matter basis (that is, with the water removed).

Water has the effect of diluting nutrients, and as different feeds have differing amounts of water, it is difficult to compare feeds on an ‘as-fed’ basis. As-fed means as you would feed them to the horse, water and all. Green growing grass can vary anywhere between 20% and 50% DM (so containing 80% to 50% water) with the DM increasing as the plant matures, flowers, sets seed and then dries off. Most hays vary between 85% and 90% DM: any wetter (lower DM) would result in mouldy hay, any drier and the hay would disintegrate when you handle it. Harvested grains are around 90% to 95% DM as are pelleted or other processed feeds such as micronized, flaked, rolled or extruded products.

Horses evolved to eat large amounts of low quality roughage, so need to be given the chance to chew for up to 16 hours a day.  It is important to understand that low quality means low in energy and protein, not mouldy or dusty. Grasses and hay are sources of roughage; whereas grains and pellets are collectively known as concentrates, as they are a concentrated form of energy (and/or protein). All horses’ rations should be formulated using roughage as the basis then adding concentrate only if energy needs cannot be met for the particular class of horse.  A horse should receive a minimum of 1.8 to 2% of its body weight dry matter per day. This should be enough to maintain adequate gut fill and, through careful selection of feedstuffs, give the horse sufficient opportunity to chew for long periods of time.  It is worth remembering though that horses can eat up to 3% or more per day (especially if the food is very palatable) and ponies up to 5%, hence why some horses and ponies are prone to being overweight.

In drought conditions, it is easy to provide the horse with sufficient energy, protein and other nutrients without satisfying the dry matter component. It is often easier to source good quality hay such as legume hay (lucerne, clover or vetch) which is relatively nutrient dense. It is highly palatable and consumed more rapidly when compared to cereal hay (wheaten or oaten) or pasture hay (ryegrass or mixed grasses).  As good legume hay contains a high proportion of leaf, which is easily chewed, a horse may consume several kilograms in an hour whereas the same weight of cereal/grass hay may take three times as long. The aim should be to prolong eating as much as possible. This may minimise the damage horses do to wooden fences and the bark of trees that they tend to chew because they are bored and have this urge to chew.

Legume hay is generally a little higher in energy, and much higher in protein and calcium than cereal or grass hay. It is usually more expensive too. Ideally, a combination of hays should be fed in a ration to reduce the amount of protein and increase the amount of time spent eating. Any type of hay should be weighed to avoid either over-feeding (in the case of legume hay) or under-feeding (in the case of cereal or grass hay). Although this sounds tedious, especially if you are feeding a large number of horses, if you can work out the weight of the hay in relation to its volume (such as filling a hay bag) then you only need periodically weigh what you have measured out, just as a check.

You should also know what body condition your horses ought to be in. Given the poor season, body condition scores between 2 and 3 on a scale of 0 to 5 are currently seen as acceptable. This means the horse’s ribs are just visible or just covered but easily felt, a narrow but firm neck with no crest, the backbone is covered but may be felt, the rump may be flat either side of the backbone, the croup is defined with some fat coverage and the pelvis easily felt. There may be a slight cavity under the tail. The horse’s coat should be shiny though.  At this time of year, even pregnant mares can be safely maintained in this body condition. It is not until the last three month of pregnancy that nutrient demands of the mare increase dramatically.

There are 5 main classes of horse used when determining nutritional needs of the horse. These are maintenance, growing, breeding/gestating, lactating and working horses. All have differing energy and protein requirements – although in reality protein does not vary that much. A maintenance horse is defined as an adult horse that is not in work, pregnant or lactating. It is neither gaining weight nor losing weight. Requirements for a maintenance horse are the foundation on which other classes of horse nutritional requirements are based. (It is a little like dry sheep equivalents (DSE) used in livestock enterprises.) An average horse at maintenance is considered to weigh 500 kg. It requires about 70 megajoules (MJ) per day digestible energy, about 600 g crude protein (CP), 25 g calcium (Ca) and 18 g phosphorus (P) in 9 to 10 kg of dry matter. You should also provide salt (sodium chloride) as a lick. These are the most important nutrients you need to be concerned with, despite what the supplement companies will tell you. Vitamin and mineral deficiencies are very rare in horses except for those minerals already mentioned.

So how much feed per day should each class of horse be getting? Table 1 gives you a guide to what a suitable ration may look like. Information is based on a horse having limited/no access to pasture and any pasture is of low quality. Remember to use the KISS principle when feeding your horses (Keep It Simple, Stupid).

Table 1. Nutrient Requirements and Feed Supply for Different Classes of Horse

Based on NRC (2007) Nutrient requirements for horses, National Academy of Sciences, Washington DC.