Feeding Pregnant Mares

Over recent years, a great deal of research effort has been focused on the nutritional requirements and feeding management of breeding horses. Although large sums of money are often spent on the purchase of breeding farms and stock, upgrading facilities, promoting stallions and raising young horses, relatively little attention is given to ensuring optimum nutrition of broodmares.

Optimum fertility and proper balanced nutrition are inter-related. An adequate energy intake, matched to the mare's requirements to achieve and maintain optimum condition, is paramount to success in horse breeding.

Pregnant mares should be maintained in moderate body condition (condition score 2.5-3). Many experienced horse breeders feed to maintain a pregnant mare in working condition rather than show condition. Many hobby owners overfeed mares in an effort to produce large, strong foals. However, a mare in trim to fleshy condition will normally deliver a foal within the acceptable range of foal birth weights.

THE FIRST EIGHT MONTHS OF PREGNANCY
During the first eight months of pregnancy most mares can maintain themselves on good pasture, with minimal supplementary feed, as long as good quality lucerne or meadow hay is fed during times of reduced pasture availability or quality. Pelleted broodmare rations are suitable for maintenance during dry seasons, or in the early winter months when pasture is poor, particularly as pregnancy progresses.

Overweight mares should not be put on a weight reduction programme during the first 90 days of pregnancy. Research has shown that pregnant mares fed diets containing energy levels below their needs, had a higher risk of early embryonic and foetal abortion during the first three months of pregnancy, compared to mares kept at a constant bodyweight.

After the first 90 days of pregnancy an overly fat mare can be safely put onto a well monitored weight reducing programme. It is essential to adjust the feed intake and ensure exercise to achieve a weight loss of no more than 1% of the mare's bodyweight each week (5 kilograms for a 500 kg mare), until she reaches and maintains the desired body condition score between 2.5-3.

Plan to reduce the concentrate feed in a step wise manner by about 50-70 g/100 kg bodyweight each week, or alternatively restrict the mare's access to grazing and exercise lightly for 20-30 minutes under saddle 2-3 times per week. The mare should not be starved, nor fed on poor quality hay which may have trace mineral deficiencies.

During weight reduction, the mare should be provided with a supplement of good quality protein, such as one cup (200 g) of soyabean meal or 11/2 cups of canola meal per 200 kg body weight, and provided with a vitamin and trace mineral supplement which contains copper, such as Feramo-H.

THE LAST THREE MONTHS OF PREGNANCY
The unborn foal doubles in size during the last 90 days of pregnancy, so increased levels of energy, protein, minerals and vitamins are essential to support the growth of the foal, maintain condition of the mare and prepare for lactation. Dietary guidelines for a 500 kg mare in late pregnancy are provided in the table. Remember that all dietary changes should be done gradually in a step-wise manner to avoid digestive upsets.

Loss of condition in a mare during the last three months of pregnancy does not affect her foal's body weight at birth, unless she becomes very thin. However, the loss of body reserves may decrease the mare's colostrum and subsequent milk production so that her foal's growth rate and immune status may be compromised. As a commercial breeding proposition, a mare must be able to be bred and conceive again within 1-2 months of foaling. Failure to supply adequate nutrition to maintain bodyweight after foaling may reduce subsequent fertility and conception.

During the last three months before foaling, it is best to separate heavily pregnant mares from other mares and horses. A young, or timid mare, must be able to consume sufficient supplementary feed to meet her needs without being harassed or bossed away from the feeders. It is good practice to provide one extra feed bin, or locate 2 or 3 feed bins away from the main feeding area, for timid younger mares so that they are able to obtain their fair share of feed.


Nutritional Requirements/Management

· Energy
Additional energy in the form of concentrate feed must be provided to meet the demands of the unborn foal and provide reserves to prepare the mare for lactation. As a guideline, during the last three months before foaling, the level of concentrate feed and hay should be increased by an average of 10% per month to give a 5% increase in energy intake each month.


· Protein
Protein provides the amino acid building blocks for development of the unborn foal. Good quality protein with adequate lysine and other amino acids is essential for foetal development, with the requirement increasing by 30% during the last three months of pregnancy.
The protein level in the concentrate ration should be boosted to 14-16%, particularly in mares grazing grass based pastures in winter and early spring. The protein content can be economically increased by providing good quality lucerne hay in self-feeders, plus a 14-16% protein concentrate mix, once or twice daily to maintain condition.


· Fibre
Although adequate fibre is essential for efficient digestion, it is good practice to provide an energy dense, less bulky ration during the last couple of months of pregnancy. The enlarged womb may reduce hindgut digestive capacity, and a heavily pregnant mare may not be able to eat large quantities of bulky pasture and hard feed, to meet her needs.
Some experienced horse breeders recommend to add up to 10% bran in a dampened concentrate sweet feed once a day for mares during the last month of pregnancy. When mixed with 5% molasses, it may provide some laxative affect for late foaling mares grazing on dry summer pastures, as well as a little extra phosphorus to meet the elevated needs in late pregnancy. If adequate green pasture is present, bran need not be given in the concentrate feed.


· Minerals
All minerals are required in adequate amounts during pregnancy. However, almost double the amounts of calcium and phosphorus are required for foetal skeletal bone development in late pregnancy, particularly in older mares over 16 years of age.
The diet should contain 0.5% calcium and about 0.35% phosphorus during the three months prior to foaling. It is essential that adequate phosphorus be provided in the ration during the last three months of pregnancy, otherwise the mare's fertility and chances of getting in foal again within three months will be significantly reduced.
Balanced calcium, phosphorus and trace mineral supplementation is essential during pregnancy to compensate for soil and feed deficiencies and imbalances. This can be achieved by feeding both Feramo-H and Cal-Plus. Feramo-H is a vitamin and mineral supplement, while Cal-Plus contains 3 different forms of calcium plus the co-factors needed to enable the calcium to be taken up from the bowels and utilised within the body.


· Vitamins
A range of vitamins are required to ensure adequate growth of the unborn foal. The requirement for vitamin A doubles during the last quarter of pregnancy. During the winter months, a pregnant mare at pasture may not be able to synthesise sufficient vitamin D from sunlight to meet her requirements. Feramo-H will provide a supplementary source of vitamin A and vitamin D.


· Exercise
Exercise is required to keep a mare in a fit condition for foaling. Grazing provides adequate exercise in most cases, although a heavily pregnant mare in the last month prior to foaling is often less agile, and may prefer to graze within easy range of a supplementary feed area. Locating feeders and waterers well apart will help to encourage exercise. Undulating country may also help pregnant mares to exercise and maintain physical fitness. Where a mare is confined to a small area, walking in hand for 15-20 minutes daily will help to promote feed utilisation and fitness. It is risky and uncomfortable for a heavily pregnant mare to be exercised under saddle, or by lungeing.


· Older mares
Healthy, well cared for mares often breed regularly until over 20 years of age. Mares over 16 years of age should receive extra protein and calcium daily because older horses are less efficient in absorbing these nutrients. It is also wise to crush the grain for an aged mare with poor teeth to ensure she obtains the full benefit from the concentrate feed. She should also be provided with a more energy dense ration and additional protein, at approximately 200 g (1 cup) of additional soyabean meal or 300 g (1.5 cups) of canola meal daily for every 250 kg body weight, as protein utilisation is not as efficient.
A sweetened feed containing about one kilogram wet weight cooked barley per 200 kg body weight, may be given twice a week as an appetising feed in late pregnancy, particularly during very cold, wet and windy weather.


· Grass based pastures The type of pasture grazed influences the amount of calcium and phosphorus available, and the balance between them. Grasses are generally lower in calcium and higher in phosphorus than legumes. Where mares are grazing predominantly grass pastures, such as Fescues, Paspalum and Ryegrass, extra calcium must be provided to meet requirements. Provision of good quality lucerne hay as well as a concentrate feed containing supplementary levels of calcium, zinc and copper (e.g. Feramo-H and Cal-Plus).

In tropical areas, where pasture contains high levels of oxalate containing grasses such as Setaria, Green and Blue Panic, Buffel, and even heavily fertilised Kikuyu in sub-tropical areas, an extra supplement of calcium (e.g. Cal-Plus) essential to counteract calcium binding by oxalates in the small bowel.


· Legume based pastures Lucerne or legume based pastures, usually provide more than adequate calcium, but are low in phosphorus, which can result in a relative deficiency of phosphorus in heavily pregnant, grazing mares. In this case, the amount of lucerne hay should be restricted, and replaced with mixed hay, or a blend of 50:50 lucerne and cereal chaff as the base for the hard feed mix given daily, depending on availability.
Careful attention to balanced, adequate, but not excessive nutrition for broodmares provides the best start to a foal's life. Energy, protein, minerals and vitamins are all essential components of the diet and care should be taken to make sure that they are available to the mare and developing foal in the correct quantity and balance, particularly in the last 3 months of pregnancy.

Ingredient
Oats
(Whole, dust free)

Soyabean Meal
(Optional)

Lucerne Chaff
(leafy, dust free)

Cereal Chaff

(dust free)

Molasses - optional
Bran - optional (flaked)
Vitamin and Mineral Supplement
Vitamin E
Salt
Lucerne Hay (good quality, dust free)
Daily Amount
3-4 kg (6-8 litres) 8-9 months
4-4.5 kg (8-9 litres) 9-10 months
4.5-5 kg (9-10 litres) 10-11 months
200 g (1 cup)300 g (1.5 cups)350 g (2 cups)
500 g (4 litres)
450 g (3 litres)
250 ml (1 cup)
450 g (3 litres)
Feramo-H(56g) and Cal-Plus (60g)
White E or White E with Selenium (1/2 - 1 scoop)
30-40 g (1.5-2 tablespoons)
2-3 kg (1 - 1.5 biscuits)
Provides
Energy, Protein and Fibre. Increase by 250 g each fortnight from 9-11 months of pregnancy
Energy, high quality Protein with Lysine - add protein meals if meadow hay is fed or mares graze predominantly grass pastures
Fibre, Calcium, Protein - dilutes the grain intake - limit bulk between 10-11 months as growing foal reduces gut space.
Fibre, some Phosphorus - cereal chaff can be replaced by increasing lucerne chaff to 750 g (6 litres) in the last month of pregnancy to limit bulk.
Add to dampen the ration. Helps prevent sifting out of supplements or powders blowing away.
Fibre, Phosphorus. Widely used by breeders dampened with molasses. May help avoid constipation in heavily pregnant mares, but not as effective as green pasture intake.
Essential Vitamins and Minerals including calcium, phosphorus and selenium. Helps balance the ration, contains Vitamin A, D, iodine and other trace minerals required for subsequent fertility.
Vitamin E - maintains body stores and may protect against selenium deficiency in the rapidly growing foal.
Aids palatability of the ration and encourages water intake.
Fibre, Protein, Calcium. Adjust to pasture intake. Good quality meadow or clover hay can be provided in place of lucerne hay.



Document Contents © Leverton & Co. 2004
This article has been adapted from the recently published book "Feeding and Nutrition of Horses - The Making of a Champion", by Dr John Kohnke, one of Australia's leading equine vets and nutritional advisors. Vetsearch International