Discover the Key Factors for a Mare's Fertility & Reproduction Success

Broodmare management and optimal nutrition are both vital to a successful mating. A range of factors may negatively influence broodmare fertility, some of which are simple to correct while others are more challenging or even inevitable:

Age As the mare ages her fertility will decline.  Studies have shown that by 15 years of age fertility is reduced by 10-20%, although a higher risk of pregnancy losses has been noted in mares aged between 9-13 years old
Stallion Certain stallions can have a cycle conception rate as low as 45% but still achieve excellent pregnancy rates due to repeated coverings
Reproductive status Barren, slipped or rested reproductive status increases the likelihood of pregnancy loss
Health Issues resulting in contamination or infection of the reproductive tract or a malfunctioning of the hormonal system can result in reduced fertility
Nutrition Fertility and pregnancy require nutritional support and inadequate nutrition is likely to reduce reproductive success
The Role of Diet and Condition on Fertility and Conception in Mares

A well-balanced diet can improve fertility and reproductive success through several routes, most notably the number and quality of eggs, the environment for the developing foetus, and the health of the neonate. Research has shown a direct link between the effect of nutrition and body condition on reproductive efficiency in breeding mares. Mares coming into the breeding season in good to moderate body condition (3-3.5 out of 5) start cycling earlier than mares in poor body condition and mares have better conception rates when in a rising plane of nutrition. 

A poor Body Condition Score in Mares can Negatively Affect Ovulation

Brood Mares with poor body condition scores (<3) at mating have been shown to be more likely to suffer from irregular ovulation, reduced conception rates and an increased chance of early embryonic deaths.  As many early embryonic deaths occur in the first 40 days of pregnancy it is a nutritionally critical time period, especially for the under-weight broodmare. 

Young maiden mares which have recently come out of racing will have nutritional requirements above that of a mature broodmare as they are still growing. Some maiden mares returned out of training may be both underweight and stressed. Thin maiden mares should be fed so that they are gaining weight and in a positive energy balance coming into the breeding season. 


High Body Fat Scores in Breeding Mares can Reduce Conception Rates

On the other hand, mares with high body fat scores (>3.5) have been reported to have reduced conception rates (Figure 1) and are more likely to suffer from longer oestrous cycles which can be due to a persistent corpus luteum, increased risk of abnormal follicle maturation and/or insulin resistance. Some obese mares can continue to cycle throughout the winter when typically the reproductive cycling is shut down. This affects breeding efficiency in the spring. 

Obesity in Mares can lead to an increased Chance of Foaling Difficulties

Obesity can lead to difficulties during foaling and may lead to non-pregnancy related insulin resistance (IR).Broodmares know to be suffering from IR prior to pregnancy may be at increased risk of reduced reproductive function and will need a low starch diet to help normalise insulin dynamics and provide sufficient, but not excessive, calorific intake. We recommend that you contact our Nutritional team for expert advice. 


Weight loss in Mares 4-8 weeks Prior to The Breeding Season should be Avoided

To maximise reproductive efficiency the breeding mare should ideally be placed on a rising plane of nutrition three weeks prior to covering and should have a body condition score of 3-3.5 out of 5 at conceptionWeight loss 4-8 weeks prior to the breeding season, or during the first 90 days of pregnancy, may negatively affect the onset of oestrus and increase the risk of early embryonic death. Therefore, the aim for mares that are overweight should be to maintain their current condition without promoting further weight gain. 

Connolly's RED MILLS GroCare Balancer is a Top Choice Horse Balancer for Mares

A nutrient-rich horse balancer such as Connolly’s RED MILLS Grocare Balancer or a broad-spectrum multivitamin and mineral supplement for horses such as Foran Equine Chevinal can be fed to ensure optimal micronutrients are provided. If needed, additional calories can then be provided by ‘topping up’ with a suitable stud mix or cube for mares. Connolly’s RED MILLS Stud Cubes and Stud Mix will fulfill the nutritional requirements of mares in optimal body condition. 



The Broodmare's Diet Should Include Sources of High Quality Protein for Breeding Success

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. Good quality protein is rich in these essential amino acids and plays important roles in fertility. Studies have shown that mares fed a diet low in quality protein are more likely to suffer fertility problems including an increased risk of failure to ovulate and the risk of embryonic loss is increased fivefold.

Soyabean Meal is a Quality Source of Protein in the Broodmare's Diet

Soyabean meal is the most common source of quality protein included in horse feeds and is used in all of Connolly’s RED MILLS horse feed formulations. In their uncooked state, soyabeans contain the anti-nutrient factor, trypsin inhibitor. Trypsin is an important enzyme involved in the digestion of protein. The trypsin inhibitor contained in raw soyabean prevents the digestion of protein within the soya when ingested by the horse. Connolly’s RED MILLS uses state-of-the-art cooking techniques to remove this trypsin inhibitor and improve digestibility. 


Omega 3 Fatty Acids Play Important Roles in the Broodmare's Diet for Reproduction

Certain omega 3 fatty acids (i.e. eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) may help to improve the mare’s reproductive efficiency, increasing conception and live foal birth rates. They help to inhibit prostaglandin production, thereby prolonging the maintenance of the corpus luteum, which may be particularly useful for mares that have a history of abortionIn addition, omega fatty acids have also been shown to be very important for foetal developmentFlaxseed oil such as Foran Equine Kentucky Karron Oil is a rich source of omega-3 fatty acids providing omega 6 and omega 3 at similar ratios to that found in grass. Foran Equine Kentucky Karron Oil, is a premium equine oil supplement, which has the additional benefit of being emulsified, which facilitates digestive lipolysis (i.e. the breakdown of fats) and subsequent fat bioavailability.

Some Key Trace Minerals Need to be the Included in the Diet for a Brood Mare's Reproductive Success

Broodmares must receive a fully balanced diet as several essential trace minerals (copper, selenium, manganese, iodine, zinc, and iron) can influence reproductionLack of trace minerals or an imbalanced intake of minerals has been linked to reproductive issues in several animals. For example, low manganese intakes in ruminants is known to depress conception rates. All Connolly’s RED MILLS feeds contain a unique Pro Balance vitamin and mineral package to ensure your broodmares receive all the essential nutrients needed for fertility and reproductive health. 


Provision of a diet adequate in both macro and micronutrients is the foundation for equine fertility and reproduction. However, inclusion of supplemental nutrients, including omega-3 fatty acids and antioxidants, may contribute to the prevention of poor fertility parameters and improve reproductive performance.