When feeding the growing foal, the goal is to achieve a steady growth rate from birth to maturity, avoiding any severe growth depression or spurt by ensuring that all nutrients are consumed in the proper amount. This can only be achieved through a delicate balance of energy, protein, and minerals.
Growing foals have a certain energy requirement for growth. The amount of energy required by the individual foal will be dependent on its age, weight, rate of growth, environment, and any natural exercise. If too much energy is provided in the ration, the risk of skeletal disease is greatly increased. If not enough energy is provided, the growth rate will be reduced.
To provide sufficient dietary energy and protein for optimal growth and often for maximum mature size, the grain will most likely be required. This is particularly the case for rapidly growing thoroughbreds intended to be sold as yearlings. Oats are often used as the primary energy source in growing horse diets. Compared to other grains, oats are a relatively safe feed, being higher in fiber and having less indigestible starch compared to barley and corn. For growing horses requiring improved body condition (particularly as yearlings) other energy sources such as rolled barley and rice bran may be useful as these feeds tend to be “cooler” and more “conditioning”.
Fats or oils may also be added to growing foal diets to improve the energy level of the ration. Oil provides almost three times as much energy on a weight-for-weight basis and may be useful, particularly during the preparation of yearlings for sale. Each oil or fat has a blend of different fatty acids (Omega-3, Omega-6) in its triglyceride content and a correct ratio of these is essential. Canola oil is generally suitable in its pure form. Oil should be added fresh each day to the meal at feed time. Vitamin E (such as Virbac’s White-E at half the normal dose (8g)) should also be supplemented to ensure the best utilisation. While oil is energy dense, it contains no minerals and supplementation is essential for a balanced diet.
Protein is the major structural component of muscles, blood, and many other tissues. On a moisture and fat-free basis, protein constitutes 80% of a horse’s body weight. Proteins primarily provide amino acids and nitrogen for tissue growth.
Both the amount of protein and its quality or amino acid content are important for growth. A greater amount of the essential amino acid lysine is needed by the young horse for growth than is available from microorganisms in its intestinal tract and that is present in many feeds. To provide the amount of lysine needed by the horse for growth, all of the additional protein above that is provided by the grain and forage fed that is needed to meet these protein requirements should be provided by a good quality protein supplement. Table 1 outlines protein meals typically used in growing horse diets. If feeds are offered which do not contain adequate lysine, growth rate and feed efficiency will be reduced.
Table 1. Types of protein meals are often used in supplemental growing horse feeds.
|Feed||Protein %||Best form to feed to horses||Comments|
|Soyabean meal||44.5||Meal extracted||Best source of balanced protein and amino acids available for growing and performance horses|
|Full fat soyabean||38%||Granules/meal extruded||Higher energy than an extracted meal, suitable to boost energy – Very palatable, turn rancid on storage unless extruded|
|Lupins||33.8%||Clean cracked seeds||Good energy source, palatable and suitable replacement for other protein meals|
|Tick beans||33.8%||Clean cracked seeds||More commonly used in racehorse rations, may be replaced with lupins|
|Sunflower seeds||23%||Plump whole seeds||Good “cool” energy boost and coat conditioner for yearling sale preparation, lower in protein so more is required to replace high protein sources|
From: Kohnke et al., 1999.
Roughage is an extremely important part of the horse’s diet for optimal digestive function and health. Typically the roughage component will range from a minimum of 30% to 90% in the growing horse diet, depending on the breed of horse and the rate of growth. Typical roughage sources are hay, chaff, and pasture.
The mineral content of pastures varies according to soil type, plant species, season, and fertiliser history. Australian pastures are typically deficient in some trace minerals and may also provide lower than recommended levels of major minerals calcium and phosphorus. When pasture is available and makes up a large proportion of the weanling's intake, it is good practice to test the pasture for mineral levels to prevent dietary deficiencies. In these situations, a hand-fed ration containing appropriate levels of deficient minerals would be required.
Hay also provides a variable source of nutrients. Compared to “white” hays and chaffs, lucerne hay is comparatively high in protein and calcium and if this is offered as the primary roughage source, imbalances in calcium and phosphorus may exist. In these situations supplemental phosphorus may be required.
Table 2. Nutrient composition of various roughage sources.
|Roughage type||Energy||Protein||Calcium||Phosphorus||Calcium to Phosphorus ratio|
There are many essential nutrients in the growing foal's ration, but various studies have shown a correlation between the occurrence of skeletal disease in horses and reduced and imbalanced amounts of calcium, phosphorus, copper, and zinc. The incidence of these diseases decreased significantly when these minerals, particularly copper were increased in the diet.
Calcium and phosphorus are critically involved in bone growth, development, and maintenance. Without adequate quantities of calcium or phosphorus, endochondral cartilage becomes thickened, bone density and growth decrease and developmental orthopedic disease may occur. Deficiencies of calcium and phosphorus result in bone deformities and skeletal weakness.
The diet must not only contain adequate amounts of calcium and phosphorus, the animal must be able to absorb and utilize these nutrients. A sufficient excess of either mineral will decrease the absorption of the other. Thus, if the amount of one mineral with respect to the other, or the calcium to phosphorus ration (Ca:P) in the growing horse’s diet is outside a range of about 0.8:1 to 3:1, alterations in endochondral ossification may occur resulting in skeletal disease.
Vitamin D plays a vital role in the regulation of calcium and phosphorus metabolism and has a major regulatory role in bone metabolism and strength. Several studies in humans have shown vitamin D and calcium supplementation to significantly reduce fracture rates and bone loss.
Zinc is essential in bone, cartilage and hoof formation and deficiency can result in reduced appetite, retarded growth, dry thickened skin and hair loss in severe deficiencies. Copper is required for the development of bone, joint cartilage, elastic connective tissue, uptake and utilization of iron and copper containing metabolic and tissue anti-inflammatory enzymes. Deficiency can result in lameness in growing horses and anaemia.
The nutrient requirements of the growing foal are frequently greater than those present in commonly used cereal grains and forages and supplementation of these minerals is often required to assist in preventing skeletal problems.
A daily supplement of Cal-Plus with Biotin will provide key macrominerals including calcium, phosphorus and magnesium as well as trace minerals iron, zinc and manganese and Vitamin A, D and biotin which will also help to harden and strengthen hoof walls of growing horses.
A well formulated and balanced trace mineral and vitamin supplement is usually required to correct imbalances in pasture and other feed sources for growing horses. Feramo with Chromium supplies a range of essential trace minerals and vitamins and is also fortified with high quality amino acids to promote muscle development and condition.
A trace-mineralised salt lick and good quality water should always be available.
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