Equine Nutrition/Nutrient sources
There are a number of nutrient food sources for horses.
- cereal grains
- cereal by-products
- fibrous by-products
- oil by-products
The horse is in their most natural environment when they spend the majority of their day grazing on pastures. Forage constitutes the largest portion of the horse's diet, in fact it makes up the entire diet for wild horses and many domesticated horses. The natural diet for the horse is low quality herbage. Domesticated horses are often grazed on pastures that have a higher nutritive value through improvements in pasture maintenance than their wild counterparts. Horses eat forage either through grazing fresh forage directly from pastures, or a variety of forages that have been conserved in one way or another.
While many domestic horses do have opportunity to spend a great deal of time at pasture, some horses that are kept for competition purposes may be restricted entirely (stabled year 'round) or in part (limited turnout) from natural grazing. In many places in the world, seasonal growing periods results in the need to conserve excess forage for winter feeding. Conserving forage is done in a number of ways, with the goal being to preserve a digestible product with high nutrient value. It must also be palatable, of high hygenic quality, and able to be stored for long periods of time.
Forage is conserved in a number of ways:
- naturally dried in fields or barns and baled
- short chopped and artificially dried at high temperatures
- acidifying in an anaerobic environment
A common way of conserving forage is to allow the cut grasses to field dry before baling and storing it. This process is dependent on appropriate weather conditions. The harvested plant materials are typically cut at a late stage of maturity, and dried to approximately 15% moisture content. The quality of field-dried hay is quite variable both nutritionally and hygenically. Grass hay is a low energy forage with a variable digestible energy (DE) of between 4 and 8 MJ/kg). Alfalfa (also called lucerne) is higher with a DE of ~10 MJ/kg). In addition to being a higher energy source, alfalfa is also higher in protein (alfalfa is a legume and legumes are higher in protein) and it is higher in water content. Typically field-dried hay is stable in ambient conditions, however, if not dried properly, changes can occur during storage affecting the already variable quality of the product. One of the disadvantages of field-dried hay, is the potential for dust content which horses will inhale while eating the hay. One of the ways to address this is to soak or steam the hay prior to feeding it. Soaking the hay in a bucket of wather shouldn't last more than 10 minutes to minimize the loss of water-soluble nutrients.
In places where weather conditions make field drying difficult (particularly for alfalfa), another conservation method that maintains the nutritional quality and produces a highly digestible product, is to artificially dehydrate the forage at high temperatures. The hay is chopped into shorter pieces and then put into a special tank for a brief period of time at 800°C. This an expensive, but efficient process and lends itself well to drying young forage. Two downsides to this method, is the work involved with chopping the forage and, secondly, that horses will eat it very quickly. Often straw is mixed with the alfalfa to lower the protein levels in the finished product.
A third way to conserve forage is to turn it into haylage or silage. The process to do this is in effect to "pickle" the hay. It is done through an acidification process in an anaerobic environment. Technically, the existing lactic acid bacteria found naturally on the moist grasses ferments the carbohydrates into lactic acid. The lactic acid drops the pH level of the crop which acidifies it, thus reducing the spoilage organisms on the end product. The only difference between haylage and silage is in the dry matter (DM) content. Silage has a higher moisture content. This means that silage is at greater risk for microbial growth and since the horse cannot metabolize certain toxins, haylage is the more common choice for horses.
For haylage, since the grasses are cut younger, it has high digestibility and is typically lower in dust compared to hay. Horses like the taste and it reduces the need to feed cereal grains. The downside is that it has low aerobic stability - once it is unwrapped it begins to deteriorate particularly in warmer seasons.
Cereal grains have a crude protein value of about 120 g/kg Dry matter but, are considerably low essential amino acid content. Lipids make up 10-60 g/kg of dry matter have considerably low calcium content and low phosphorous. Cereal grains also have a high digestible energy content, about 12-16 MJ/kg.
Commonly utilized cereal grains are oats, barley and maize(corn). Other grains are wheat,rye, sorghum and triticale. Oats are the lowest in starch content, about 40%, while having a high fiber content(with hull). Barley has a higher energy content then oats because it has ~55% starch. At 70% starch maize has the highest energy content. To allow complete starch digestion in the small intestine, cereal grains must be processes. Processing these grains improves availability of nutrients. Processing can be simple like grinding or rolling or more sophisticated like micronisation or extrusion.
Starch should make up no more then 1 g/kg of live weight per meal. Therefore cereal grains should be feed in moderation and in small and frequent meals.
Sugar beet pulp is the most common fibrous byproduct and is generally under used. It is a very good feed stuff to give horses because is has a high fiber content and high fiber digestibility. It also has high calcium content and a moderate crude protein content. The pulp is the residue after the extraction of sucrose. The pulp is shredded or pelleted after being dried. Some sugar beet pulp has molasses added to it for palatability.
Sugar beet pulp is a great cereal grain replacer because it has a uniform composition, a better calcium content and a high dry matter digestability. Feeding sugar beet pulp has a lower risk of large intestine disturbance. When fed, sugar beet pulp must be soaked to prevent colic and choke. The recommended time is 24 hours for pelleted and 12 hours for shredded. If you use hot water you can speed up the process.
Sugar beet pulp is often added to compound mixes and complete feeds as well as bucket feeds.
Once cereal grains have been processed they leave a residue called bran. Wheat bran is the most commonly feed cereal byproduct feed to horses, however it has high levels of lignin and a poor phosphorous to calcium ratio. Wheat bran has a high water capacity and therefore a good vehicle for administering medicines. It is also very palatable and good for stimulating appetite.
There are two main kinds of oils feed to horses, vegetable oil and fish oil. Corn, soy, sunflower, rapeseed and linseed are the most commonly utilized vegetable oils. Corn is the most palatable, but it is also high in omega 6s and therefore more pro-inflammatory. Cod liver oil is the most commonly utilsed fish oil and is particularly healthy because of its high levels of omega 3s. Most oils have an energy content of 9 megajoels per kilogram. They have 2.25 times more energy then carbohydrates. The benefits of feeding oil are improved energetic efficacy, improved athletic performance, enhanced body score and less excitable behavior.
Oil byproducts are the seed meal that is left behind after the oil is extracted. Oil seed meal is high in protein and has some oil content. It is often used as a protein supplement. The highest in protein and lysine are soybean, linseed and hemp seed meal.