The feeding program of the breeding mare is an important management aspect. Feeding can affect the fertility, milk production, and the skeletal development and growth of the foal. Understanding the nutritional needs of the maiden/barren, pregnant and lactating mare is essential for the development of a proper feeding program for all stages. In this article we discuss the preparation and nutritional requirements of the maiden, barren and pregnant mare.
Preparation of the breeding mare
The preparation of the breeding mare can be a challenging task and should not be planned last-minute. It is important to start the preparation of the breeding mare in an early stage prior to covering.
A preparation time of 4-6 months is advised to increase the chance of conception and to minimize the return to the stallion or the artificial insemination rates. For both the maiden and barren mare, it is important to start monitoring her general appearance, body condition and cycles. When a young mare (2-4 years) is prepared for the her first breeding season, it is essential to monitor her development, growth and condition more closely. However, many mares are destined for breeding on a relatively later age of life. The majority of these mares have already had a successful sporting career and, based on these performances, they are chosen to become a broodmare.
The pregnant mare also needs preparation before re-covering, but the pregnancy limits to an extent how she can be managed. Monitoring of the body condition of the pregnant mare is essential to avoid mares becoming obese at parturition.
At the beginning of the breeding season it is recommended that breeding mares are maintained in a moderate to moderate-fleshy body condition (Henneke body condition score of 5-6). A moderate body condition shows no crease or ridge on the back (flat). The ribs are not visible but can be felt. Neck and shoulders are in a smooth line with the body, and the tailhead begins to feel spongy. A higher condition (body condition score of 7-8) have no significant negative or positive effects on the conception rate, anovulatory period and numbers of cycles to conception of the mare. However, a thin body condition (less than 5) is known to impair a mare’s reproductive performance.
The maiden/barren and early pregnant mare
The maiden/barren and early pregnant mare have the same nutrient requirements as the mature horse at maintenance. During the first months of pregnancy the foetus is only small. At seven months of gestation the foetus is only about 20% of the foal’s weight at birth. However, with gestation progressing, more fetal and associated mammary and placental tissue will be synthesised, and this will slightly alter nutrient requirements after five months of gestation.
The early pregnant mare should be maintained in a moderate body condition. It is recommended to feed broodmares long-stem roughage at 1.0-2.5% of the body weight per day. On pasture, broodmares can voluntarily consume up to 3.0% of their body weight as dry matter daily. However, overfeeding the early pregnant mare should be avoided, as it may lead to obesity and foal difficulties. If broodmares are ‘good doers’ the access to high-quality pasture should be restricted. Exercise is important and assists with maintaining an optimal body condition and muscle tone. All mares should have the opportunity to be turned out daily. Riding is also a good form of exercise. Most broodmares can be safely ridden up to six months, but this may vary individually.
Broodmares should be offered supplementary feeds if they are kept on poor-quality pastures or high-oxalate pastures that have low availability of calcium, such as kikuyu. Legume/grass hay, concentrates and/or supplements can be fed to correct these nutrient deficiencies. Typically, a commercially-manufactured cereal-based or low GI concentrate or home-mixed ration with additional supplements, usually up to 0.5% of the body weight per day, can be sufficient to satisfy energy, vitamin and mineral requirements of the maiden/barren and early pregnant mare.
The mare in late pregnancy
After seven months of gestation, the nutrient requirements increase significantly. In these last four months about 80% of the growth of the foal in the pregnant mare takes place. The energy, and to a greater extent, protein, calcium and phosphorus requirements increase because of fetal tissue being synthesised.
It is common that mares in late pregnancy are overfed. Breeders should maintain mares in late pregnancy in a moderate to moderate-fleshy body condition. The main diet of broodmares should consist of quality forages (pasture and/or roughage). Roughage can be fed at 1.0-2.0% of body weight per day. Generally, mares in late pregnancy need to be supplemented with concentrates or supplements to meet nutrient requirements.
The protein quality and amount of amino acids, especially lysine, is very important in the diet of the mare in late pregnancy. It is recommended to feed a protein supplement such as sunflower meal, extruded lupins and/or soybean meal or a commercially-manufactured concentrate pellet high in lysine. If the broodmare is given good-quality forages, a high-protein concentrate can be fed up to 0.5% of the body weight per day. Broodmares offered poor quality forages can be fed up to 1.0% of the body weight per day. If the amount of roughage or access to pasture is reduced to prevent obesity, a high-protein concentrate can be offered at 0.5-1.0% of the body weight per day to meet requirements.
Always feed the pregnant mare an adequate amount of minerals. To meet mineral requirements, concentrates should contain added minerals or a mineral supplement has to be mixed into the feed. Inadequate and inappropriate levels of minerals in the diet of broodmares can cause abnormalities in the skeletal growth and development of the foal, a condition commonly known as Developmental Orthopaedic Disease (DOD). Especially calcium and phosphorus levels have to be sufficient and it is recommended to feed calcium and phosphorus in an acceptable ratio of 1.4-1.8:1. It is also important that trace minerals intake is sufficient. Trace minerals such as iron, zinc and copper are stored as a reserve in the liver of the foal and supplies the foal once it is born.
A selection of the National Research Council (NRC, 2007) recommendations of the daily nutrient requirements of broodmares in early and late gestation are listed in Table 1.
In summary, breeders should aim to provide all necessary nutrients in the diet of their broodmares. Always take care that no overfeeding is happening when formulating the diet of broodmares, as this may cause foal difficulties. Proper feeding of mares throughout pregnancy and regular monitoring of body condition helps maintain fit broodmares and is essential for the development of healthy foals.