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The correct management and feeding of breeding mares are important factors for the production of healthy foals. Horse owners invest a lot of time, money and effort in deciding which stallions to cover their mares. Management and nutrition should be planned to give foals the opportunity to express their full genetic potential.
At any time after January 1 (in the Northern Hemisphere, and as of July 1 in the Southern Hemisphere), mares are giving birth on many farms. The nutrition of breeding mares must be divided into 3 categories:
The first 2/3 of gestation are the least demanding. Mares can be kept in a body condition of 5 or slightly above. During early pregnancy, the weight of the fetus is small relative to that of the mare. Mares must be fed according to their maintenance requirements and activity level. It will require 1 or 1.5% of their body weight in forage or its equivalent as a source of fiber plus a sufficient amount of grain or concentrate to maintain weight. If alfalfa hay is used, a properly formulated grain containing 10% -12% protein and guaranteed levels of lysine, methionine, calcium, phosphorus, copper, zinc and vitamins will be required.
If using oat hay or other grass (Rye grass or other grass), it is suggested to use a concentrate formulated with 12% – 14% protein. Concentrate or grain levels must be adjusted to maintain desired body condition. Clean, fresh water and salt must be available at all times.
The last 3/3 of gestation adds nutritional demands to the broodmares. The fetus can gain half a kilogram per day, due to bone growth and body development. The NRC (National Research Council) shows an increase of around 20% in the ED (Digestible Energy) in the maintenance requirements for the eleventh month of gestation. A concentrate with 14% – 16% protein is adequate to provide the largest amounts of amino acids such as lysine and methionine that are required at this time, as well as calcium, phosphorous, copper, zinc and other trace minerals and vitamins required for proper development of the product in the uterus. A recent study has documented that adequate mineral supplementation to broodmares improves cartilage quality in foals at 150 days of age.*
The greatest increase in nutrient demand for breeding mares occurs at early lactation. According to the NRC data, the energy requirement is increased by up to 70% and the protein requirement is doubled. There are also increases in comparable minerals.
If the nutrient intake is not enough, the mares will lose weight and remove minerals from their own bodies, reducing their chances of becoming pregnant again early. During lactation, the mare will consume 2.4-2.8 kilograms of forage and food for every 100 kilograms of body weight. The serving of grain or concentrate should be gradually brought up to 900 – 1500 grams per 100 kilograms of body weight to maintain milk production and body condition. Free access to water and salt must be maintained at this stage. Decreased body condition is an indicator of a negative energy balance with potential negative effects on production and early pregnancy return.
The end of gestation and lactation are two key periods in the life of the breeding mares (and the owner). Proper veterinary care (deworming, dental care, vaccinations) and proper nutrition are essential for the development of the foal this year and the next as well.
*(World Equine Veterinary Review, Volume 2: No. 4, p. 36, 1997.)