Feeding the Lactating Mare

Published in Horses and People Magazine

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

In part 2 of the breeding horse series “Feeding the Broodmare” the preparation and feeding management of the maiden/barren and pregnant mare were described. It highlighted the importance of having a proper feeding program throughout the pregnancy and that overfeeding should be avoided.  These management aspects assist the mare with maintaining a moderate (fleshy) body condition, which reduces the chance of having foal difficulties at parturition. A healthy and fit broodmare is also better prepared for her next challenges; the lactation period and a new pregnancy. This section will continue with the nutritional needs and management of the lactating mare.

Nutrient requirements

The daily nutrient requirements of lactating mares are very high and can be compared with those of racing horses in heavy training.  The mare will produce approximately 3.0-3.5% (early lactation) and 2.0-2.5% (late lactation) of her body weight in milk per day.  Important nutrients are secreted by the mare to supply her foal with energy, protein, fat, carbohydrates, vitamins and minerals for optimal development and growth. To correct these nutrient losses and at the same time support maintenance requirements, lactating mares must consume adequate amounts of quality feeds. A selection of the daily nutrient requirements of lactating mares are described in table 1. These requirements are recommendations of the National Research Council (NRC, 2007).

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

The lactating mare should receive high quality forages (pasture/legume hay) at  1.0-2.0% of the body weight per day. However, on pasture they can voluntarily consume up to 3.0-3.5 % of their body weight as dry matter daily. In most countries, grazing lactating mares have to be supplemented with forages, concentrates or supplements to meet their nutrient requirements. Lactating mares in early lactation can be offered daily a total diet of forages (pasture and/or hay) to concentrates in a 50:50 or 60:40 ratio. A 65:35 or 70:30 ratio of forages to concentrates  can be supplied to mares in late lactation.

Legume hay such as lucerne hay or chaff are good quality forage for lactating mares. Lucerne hay and chaff have a higher protein and energy content then grass hay. Grass hay can be fed in larger amounts and must be supplemented with a concentrate to correct nutrient deficiencies.

A commercially manufactured high-energy dense concentrate (15-17% protein) at 1.0-2.0% (early lactation) and 0.5-1.5% (late lactation) of the body weight can be offered daily to meet requirements. Breeders that feed grains must complement the diet with a protein supplement. Lactating mares need large amounts of quality protein. Protein quality is determined by the essential amino acids present and their relative amounts. Soy bean, lupins, and whey protein supplements are rich protein sources that contain high amounts of essential amino acids.

Soybean meal is generally used and can be mixed into grain diets (up to 0.5 kg per day). However, most breeders offer their mares concentrate pellets. It is advised to use a commercial concentrate that is designed for mares. To prevent digestive upset, concentrate feeds must be gradually increased with 0.3 kg per day. Moreover, if  mares receive more then 3.0-3.5kg of concentrate feed per day they should be fed twice or three times a day. Concentrate feeds can be reduced after 3-4 months of lactation when milk production declines.

There are horse breeds that are very “good doers”. Generally, they don’t have to be fed extra energy or protein and require only a vitamin and mineral supplement.  Like with the pregnant mare, if they are “good doers”  access to pasture can be restricted. Always take care that the mare is offered a concentrate high in protein, vitamins and minerals to meet her requirements. In addition, some exercise can assist with keeping the mare in an acceptable body condition.

On the other hand there are some mares that tend to become very lean at the peak of the lactation period. A negative energy balance in lactating mare should be avoided because it affects not only the milk production but it is also known to impair the reproductive performance. Lactating mares that have difficulties maintaining body condition can be given a fat-supplement. Vegetable oils (e.g. linseed, sunflower seed or canola) or feed products such as copra meal and rice bran can be added to the concentrate diet to safely increase the energy density. Fat-enriched diets can assist with maintaining a positive energy balance and adequate milk production.

Important nutrients are secreted by the mare to supply her foal with energy, protein, fat, carbohydrates, vitamins and minerals for optimal development and growth.
Photo by Reindert Jansen

Effect of nutrition on milk production and composition

Energy and protein intake can affect the milk production and composition (amino acid and fatty acid profile).  Restricted energy or protein intake is known to reduce milk production. In addition, some studies observed that excess energy and protein intake may also result in a decreased milk output. Mares that were at or above a moderate body condition, in particular obese mares, have been shown to produce less milk when extra energy or protein was fed. A decreased milk production can influence the nutrient supply to the foal which may affect its development and growth.

In last months’ article the importance of minerals and trace-minerals in the diet of the late pregnant mare were discussed. Inappropriate levels in the feed of a pregnant mare can affect the skeletal development of the foetus and may result in Developmental Orthopaedic Disease (DOD). The fortification of trace minerals in the diet of lactating mares appears to be not as important as for the late pregnant mare because milk contains only small amount of trace minerals. However, it is essential to supply also the lactating mare with sufficient amounts of trace-minerals and minerals, especially calcium and phosphorus. After foaling the skeletal growth of the foal will continue and a healthy foal grows quickly. Inadequate amounts of calcium and phosphorus in the milk may affect the normal growth of the young foal.

Excess energy or protein intake can also increase milk production. Mares, particularly those in a negative energy balance, can increase milk production when more energy or protein is fed. This may cause foals to ingest too much milk. Excessive milk intake may cause foals to grow too fast which increases the risk of developing DOD. A higher milk intake by the foal may also cause digestive upset like colic and scouring. In part 4 the feeding management of the foal will be described more closely.

In summary, the lactating mare should be offered a well-balanced diet that contains adequate amounts of energy, protein and minerals to support milk production and maintenance requirements. A positive energy balance will support the reproductive performance and the development and growth of the newborn foal.

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