The goal of feeding growing horses is to achieve a steady growth rate from birth to maturity.¹ Several strategies are recommended including:

• Creep feeding of nursing foals.

• Use of formulated, age-specific supplements.

• Use of added dietary fat for more safely increasing the digestible energy (DE) of the ration.

•  Allowing unlimited access to grasses and limited access to legume forages based on DE requirements for weanlings.

• Allowing unlimited access to grass and legume forages for yearlings.

These guidelines result from the following review of literature concerning the feeding of growing horses.

 Supplementing Growing Horses
Supplementation of diets for growing horses is required because protein, calcium, phosphorus, zinc, and copper needs for rapid growth are frequently greater than the amounts of these nutrients present in cereal grains and most forages. Digestible energy (DE) needs are greater than the amounts provided by forages. When less than the recommended amount of protein/Mcal DE is fed, feed consumption, protein digestibility, and growth rate may be reduced.² Inadequate amounts of DE will be consumed if the feed is too low in DE or protein.³Weight gain and skeletal growth were reduced in horses fed inadequate protein compared to recommended amounts, but increased protein over recommendations did not affect weight gain or skeletal growth.⁴ Also, concentrates should meet the need for lysine, the first limiting amino acid, or growth rate will be slowed.¹

Decreased dietary energy slows growth rate. A slower growth rate decreases the need for other nutrients and masks other nutrient deficiencies. If growth rate is slowed sufficiently, mature body size will be reduced,¹ however, developmental orthopedic diseases (DOD) are less likely to occur. At a faster or normal growth rate, if dietary deficiencies of calcium, phosphorus, copper, or zinc are present, DOD can occur. Even without these deficiencies, excessive dietary energy and protein result in a predisposition to DOD. Bone growth and size increase, but bones are more porous.⁵ This results in increased susceptibility to "bucked shins" or stress fractures of the cannon bone.⁶ A calcium or phosphorus deficiency can also decrease growth, and decreased height gain is a result of insufficient dietary phosphorus.⁷

It is recommended that the only salt source available also contain calcium, phosphorus, copper, and zinc, and also selenium in areas with known selenium deficiency.¹ Growing horses should not be expected to consume enough minerals free-choice, since they tend to be picky eaters compared to mature horses. Top-dress MoorMan's® GROSTRONG® Minerals for Horses, and use MOORGLO^TM or NATURAL GLO®* stabilized rice bran as added fat sources.

Do not give excess grain to growing horses. Fat or oil may be added as described elsewhere.⁸ Up to 10% fat is well accepted and will increase growth rate and feed efficiency and decrease feed requirements of both weanlings and yearlings without any detrimental effects.^{9, 10} Highfat diets may also help prevent DOD. One possible method is that fat decreases postfeeding insulin secretion,¹¹ which decreases the conversion of the thyroid hormone thyroxine (T4) to triiodothyronine (T3), resulting in higher plasma T4 and lower T3 concentrations,¹² which have been shown to be a factor in DOD.¹² NATURAL GLO is a palatable, nutritious, and safe energy source that contains 20% vegetable fat and essential fatty acids, amino acids, vitamins, and minerals. MOORGLO is a highly palatable, pelleted NATURAL GLO product containing 13.5% fat. Both should be fed with MoorMan's GROSTRONG Minerals. Finally, growing horses should be fed individually.

The effects on feed intake of the normal pecking order in horse herds are more detrimental in rapidly growing horses than other horses. Young horses can't compete for food with mature horses.

Feeding Nursing Foals
Milk from well-fed normal mares meets foals' needs for about two months.¹³ Normal foals will consume 20-25% of their body weight daily in milk for the first five weeks and 17-20% thereafter.¹⁴ The more milk consumed, the less feed will be consumed. Unsupplemented foals will eat something, ie. grass, straw, manure, or whatever else is available. Most foals will nibble on the mare's grain and will progressively eat more, but at five months will eat only 50% of the time compared to 70% for the mare.¹⁵

Foals should be creep fed a well-balanced diet as young as possible, at least by one month of age. This helps ensure that they are consuming adequate amounts of feed when mares' milk ceases to meet their needs at about two months. Even as young as three weeks of age, the foal's efficiency of concentrate utilization is high, with the foal gaining about 1 lb for each 4 lb of concentrate consumed. Feed efficiency is 1 lb of gain per 7 lb of concentrate at four months.¹⁶ Creep feeding eases the transition at weaning and meets the needs not supplied by milk after two months. Creep feeding a well-balanced diet helps prevent growth spurts, which increase the risk of DOD and should be avoided.

There was no difference in average daily gain before one month in creep fed vs control foals, but from one to two months of age, average daily gain was 2.54 lb/d vs 2.07 and from two to three months, 2.96 and 1.36 lb/d, respectively.¹⁷ In another study with Thoroughbred foals aged four months until weaning, creep fed foals gained 2.2 lb/d vs 1.8 lb/d for controls.¹⁸

A combination of three parts of SENIORGLO® (14% protein) and one part ShowBoost^TM (25% protein) makes an excellent creep feed. It contains highly digestible fibers, NATURAL GLO stabilized rice bran, vitamin and mineral fortification, and less cereal grains than typical foal feeds, for reduced risk of DOD in susceptible horses. Nursing foals should be offered 0.5 to 0.75 lb of the above mix per 100 lb of body weight daily.

Feeding Weanlings and Yearlings
Weanlings should have free access to grass forages, but not legumes. Weanlings can consume 20-50% more DE than required for moderate growth and maximum potential mature size if given unlimited access to legume forages and/or grain concentrates. Excessive DE intake can result in DOD.¹⁹ Limit legumes to the amount needed to meet DE recommendations for moderate to rapid growth.¹

Yearlings can have unlimited access to legume forages because they are unlikely to overconsume DE.¹ A fast growth rate does not increase mature size but increases the risk of DOD. However, the risk of DOD is reduced after one year of age, since 90% of growth occurs during the first year. Also, most of the deposition of bone mineral content occurs by one year, but bone mineral content peaks at three to four years of age.²⁰

As the foals grow into weanlings and yearlings and require less protein relative to energy, POWERGLO or GROSTRONG 13% Pellets can be fed along with NATURAL GLO or MOORGLO and smaller percentages of ShowBoost. Protein percentage in the concentrate should be determined considering protein content and rate of intake of the forage and age of the horse. Be sure to follow feeding recommendations and monitor each horse individually. Weanlings should be offered about 1.0 to 1.7 lb of the above concentrate mix per 100 lb of body weight daily. Yearlings should do well on 0.5 to 1.0 lb concentrate mix per 100 lb of body weight daily.

Example Rations for Growing Horses
Prepared by Pat Cassady, Equine Specialist, NATURAL GLO/ADM Alliance Nutrition

HAY ANALYSIS	Protein	Calcium	Phosphorus	DE (horse)	ADF
Timothy Hay	11.3% (51.26 g/lb)	0.46% (2.08 g/lb)	0.26% (1.18 g/lb)	880 Kcal/lb	33.1%
Mixed Alfalfa Hay	13.7% (62.15 g/lb)	0.99% (4.47 g/lb)	0.20% (0.90 g/lb)	880 Kcal/lb	37.9%

Click on a Chart to view an enlargement

Weanling - 5 Months, 400 lb body weight, expected mature weight 1100 lb, 1.25 lb daily gain	Weanling - 8 Months, 500 lb body weight, expected mature weight 1100 lb, 1.25 lb daily gain
Yearling - 12 Months, 650 lb body weight, expected mature weight 1100 lb, 1.0 lb daily gain	Yearling - 18 Months, 830 lb body weight, expected mature weight 1100 lb, 1.0 lb daily gain

 

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