Feeding the Broodmare

Published in Horses and People Magazine

By Mariette van den Berg, BAppSc. (Hons), MSc (Equine nutrition)

Photo by Arabian Horse Stud Europe

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 the following section the preparation and nutritional requirements of the maiden/barren and pregnant mare will be described. The nutrition and feeding management of the lactating mare will be explained in part 3 of the breeding horse series.

The 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 to 6 months is advised to increase the chance of conception and to minimize the return to the stallion or the artificial insemination (AI) 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. Majority of these mares have already a successful sport career and based on these performances they are chosen to become a broodmare.

The pregnant mare need also preparation before the 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 the 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 (<5) is known to impair the 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 5 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 have to 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 6 months, but this may vary individually.

Broodmares should be offered a supplement if they are kept on poor quality pastures or high-oxalate pastures that have low availability of calcium such as kikuyu. Concentrates or supplements can be fed to correct the nutrient deficiencies. Typically a commercially manufactured cereal-based concentrate, 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.

This image shows two Dutch Warmblood broodmares in late pregnancy (months 10 and 11).They are in good body condition (moderate fleshy) and still show some muscle toning in the hindquarters. Mariette worked on this stud and helped with the feeding management. Photo by Albert Akkerman

The mare in late pregnancy

After seven months of gestation the nutrient requirements increase significantly. In these last 4 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 maintained mares in late pregnancy in a moderate to moderate fleshy body condition. The main diet of broodmares should consist of good 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 concentrates high in lysine or use soybean meal, whey protein or lupins as the protein supplement in the feed mix. 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.

Feed the pregnant mare always an adequate amount of minerals. To meet mineral requirements concentrates should contain added minerals or a mineral supplement have 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. In part 4 more information about DOD will be covered.

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 maintaining fit broodmares and is essential for the development of healthy foals.

Table 1. Selection of daily nutrient requirements for pregnant mares (per 100kg body weight*)

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