Essential Nutritional Needs of Late Pregnancy & Lactating Mares

Understanding the pregnant mare’s nutritional requirements, and how best to meet them, is key for the health of both the mare and the foal.

During the last trimester of pregnancy, the equine foetus develops rapidly; over 60% of total foetal growth occurs during this period. This phase is also critical time for development of the foetal skeletal and muscular structure, as well as respiratory, endocrine and digestive systems. To support this growth, there is an increased rate of nutrient transfer across the placenta and the pregnant mare’s requirements for most nutrients increases substantially. Dietary deficiencies during this stage can result in the mare utilising her own body reserves; resulting in weight loss, reduced birth weights and potentially an increased risk of DODs in the foal.

Similarly, early lactation presents a period of substantial physiological stress for the broodmare. The lactating mare’s nutrient needs are greater than those of any other class of horse, with the possible exception of the racehorse in training. During this time, the lactating mare must recover from the stress of giving birth, produce milk, and potentially re-breed; hence, correct nutrition is of vital importance.

Calorie Requirements of the Broodmare during Late Pregnancy & Lactation

During late pregnancy, the broodmare’s calorie requirements increase by almost 30%, and by peak lactation (Figure 1), when the mare can be producing milk at a rate of 3% of BW/day, they will have almost doubled. 

Undernutrition during pregnancy will mean that the mare ‘robs’ her own bodily stores to nourish the foetus. This will result in loss of condition, which may prolong gestation, and depletion of vital mineral stores. Loss of body reserves during late pregnancy and lactation can also result in lower colostrum quality, poor milk production and reduce re-breeding success. On the other hand, excessive weight gain during late pregnancy can lead to problems at foaling and increase the risk of issues such as laminitis. 


Monitoring the Mare's Body Condition during Late Pregnancy and Lactation

Monitoring the pregnant or lactating mare’s body condition, and modifying calorie intake as necessary, is essential. Ideally, mares should have a condition score of 3-3.5 out of 5 or 5-6 out of 9. It is worth noting that in late gestation mares may have less fat cover over the ribs due to the weight of the foetus and associated tissues. Thus, more emphasis should be placed on other locations of fat accumulation (i.e. the neck and hindquarters). 

Protein Requirements of the Mare during Late Pregnancy & Lactation

It is critically important to meet the pregnant mare’s requirements for protein during gestation, as the foal’s birth weight is dependent to a large degree on protein deposition. Protein requirements practically double in late pregnancy and by peak lactation are almost three times higher than maintenance requirements. In addition, research has found that protein restriction during the last 90 days of pregnancy may reduce the ability of the newborn to absorb essential antibodies from the colostrum. Studies have also shown that lactating mares fed inadequate or poor-quality protein produce less milk, and have smaller foals, compared to those fed optimal levels of high quality protein. 


Protein is a Crucial Part of the Breeding Mare's Diet

Protein is made up of non-essential and essential amino acids. The latter cannot be made in the body and must be provided in the diet. Essential amino acids such as lysine and methionine play important roles in both foetal growth and milk production. Indeed, the efficiency of conversion of crude protein to milk protein is affected by the quality of the protein fed. The main source of quality protein in Connolly’s RED MILLS feed is soya, which is rich in essential amino acids. 

Essential Vitamins & Minerals in the Broodmare's Diet

Meeting the broodmare’s requirements for vitamins and minerals is especially critical during the last trimester and lactation. Minerals such as calcium and phosphorus are necessary for foetal bone development and must be provided in the correct ratio, ideally 2:1. Failure to provide optimal levels of calcium and phosphorus in the diet will mean that the mare draws these minerals from her skeleton, which can result in bone demineralization, as well as a decrease in milk production. 


Late Gestation Diet is Crucial for the Foal's Current & Future Health & Anatomy Soundness

During late gestation, the foetus accumulates stores of minerals (iron, zinc, copper, manganese) in the liver to support rapid growth post-parturition. The foetus has developed this nutritional strategy because a lactating mare’s milk is quite low in these minerals. Indeed, studies have shown that providing the pregnant mare with adequate copper is an important factor in reducing the risk of bone and joint maturation problems in the foal. Introducing a foal supplement after it is born, does not have the same effect of minimising developmental disease. Consequently, supplementation with Foran Equine Copper Max Paste, a chelated copper and zinc supplement for horses, may be beneficial during the last trimester. 

Adding Supplements to the Pregnant Mare's Diet Can be Extremely Beneficial

Optimal vitamin provision is also vital, particularly when feeding preserved forage, which contains less vitamins than fresh pasture. For example, studies have suggested that adding an equine supplement to your mare’s diet such with vitamin E, above requirements, can help improve the immunoglobulin (IgG) content of colostrum and hence immune function in the neonate. Thus, maiden mares and those with a history of poor colostrum quality may benefit from an additional vitamin E supplement such as Foran Equine V.S.L) is a great option as a supplement for pregnant mares. 


Best Feed Choices for Brood Mares during Late Pregnancy and Lactation

Most foaling outside the natural breeding season, or those prone to weight loss, are likely to require a higher concentrate feed intake. In this case, a specific stud feed option such as Connolly’s RED MILLS Stud Mix or Cubes is an ideal feed for mares and foals. Alternatively, if straight cereals (e.g. oats) are being fed, we recommend our Oat Balancer Mix or Pellets, as these horse balancers have been specifically formulated to balance the micronutrient, including the calcium to phosphorus ratio, content of cereals, which is a great nutrient-rich horse feed options for mares. 

RED MILLS Grocare Balancer is a High Concentrate Low Volume Horse Feed Balancer

In the last month of pregnancy, when the foal occupies much of the abdominal cavity, it is common for the mare’s appetite and total feed intake to reduce. At this point, it can be beneficial to add a small amount of Connolly’s RED MILLS GROCARE Balancer to the ration, which provides a highly concentrated source of essential micronutrients. Foran Equine B-Complete, a highly palatable B-vitamin supplement for horses, is also immensely useful at enhancing appetite. 


RED MILLS GroCare Balancer Allows the Mare to Receive Vital Nutrients Without the High Calories

If the mare becomes overweight, during later lactation or in preparation for weaning, calorie intake can be reduced by limiting the amount of Connolly’s RED MILLS Stud Mix or Cubes fed and adding a horse feed balancer (e.g. Connolly’s RED MILLS GROCARE Balancer) to the ration. This will ensure the mare continues to receive all the vital micronutrients while allowing calorie intake to be adjusted according to the individual by feeding more or less Stud Mix/Cube. 

Adding Supplements to Mare's Feed will Benefit the Foal in it's Early Days

Many breeders also like to feed pregnant or lactating mares a supplement to support foetal and early bone development. Foran Equine’s Cal-Gro, our mare and foal supplement contains an ideal ration of calcium and phosphorus plus MSM, essential amino acids, chelated copper, manganese, and vitamin E all of which play a role in supporting skeletal and joint health. Feeding a source of omega-3 fatty acids (e.g. Foran Equine Kentucky Karron Oil), our premium oil supplement to mares during late pregnancy and lactation is also beneficial, as it has been shown to improve colostrum quality. 


Changes to the Broodmare's Diet Should Always Be Gradual

It is important to remember that any changes to the mare’s diet (forage or hard feed) must be introduced gradually, ideally not within the two weeks prior to foaling, to help avoid the risk of gastrointestinal upset. Likewise, the daily ration should be divided into 2-3 meals (not exceeding 400g/ kg bodyweight/ meal) to ensure maximum digestive efficiency and reduce the risk of problems associated with excessively large meals (e.g. colic). 

The critical aspect of feeding the broodmare is maintaining the mare in good condition  by meeting her energy needs while ensuring that her protein, vitamin and mineral intakes are appropriate for each stage of her pregnancy. By understanding, the mare’s nutrient needs during late pregnancy and lactation, an informed, smart and cost-effective feeding programme can be designed and implemented for your breeding mare’s best health & wellbeing.