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May 10, 2023

How to Support Fertility in Breeding Stallions

Horse turning around

Successful breeding outcomes rely on stallion fertility, which often reflects the overall health of the stallion. While management alone won’t make infertile stallions fertile, prioritizing their health year-round can promote success during the breeding season.

Since many factors that influence stallion fertility trace back to gi tract health, good digestive function is a necessary step toward optimizing fertility. Keep reading to learn how you can increase your chances of producing healthy foals by supporting fertility in breeding stallions.

Factors That Influence Fertility in Stallions

Several factors influence fertility in breeding stallions, including stress, body condition, nutrition, gi tract health and sperm quality. While you can’t alter genetic factors that impact fertility, management changes can address health factors that promote good-quality sperm.


The physical demands of collection and covering mares can increase stress in breeding stallions. One study found that stallions had elevated levels of the stress hormone cortisol during the breeding season. (Aurich et al., 2015)

Increased stress and high cortisol levels can increase the risk of gut disorders, contributing to weight loss and poor nutrient absorption. As a result, stressed breeding stallions with digestive problems can’t get the energy they need for optimal breeding performance. (Malmkvist et al., 2012)

Body Condition

Reproduction increases energy demands for stallions during the breeding season, and research shows that body condition is one of the best predictors of reproductive success. (Manyovani et al., 2011)

Breeding stallions should maintain a body condition score of 5-6 for optimal fertility. But stallions can quickly lose condition during the breeding season if their diets don’t meet their increased energy and protein requirements or if their digestive health is poor.

However, excessive body weight is also a roadblock to breeding success. Compared to fit stallions, those that are obese have worse overall health and lower fertility. These horses may also lack the athletic endurance necessary to perform breeding duties. (Hurtgen, 1992)


Beyond simply meeting energy demands and protein requirements to maintain body condition, the stallion’s diet must also provide adequate levels of specific nutrients for sperm production. New research shows that supplementation with targeted nutrients can increase sperm motility and concentration, which is linked to increased reproductive success. (Bazzano et al., 2021)

One study found that supplementation with omega-3 fatty acids can improve pregnancy rates for stallions with fertility issues. Sperm cell membranes contain high levels of DHA, an omega-3 fatty acid, so low DHA levels can significantly reduce fertility. (Brinsko et al., 2005)

Antioxidants like vitamin E, vitamin C and beta carotene can also help support increased sperm production. (Morte et al., 2008)

Gut Health

While you can quickly address nutrient deficiencies that impact fertility with specific supplements, supplementation is only effective in horses with healthy digestive tracts. Even with a balanced diet, poor digestive function can lead to weight loss and nutrient deficiencies.

For example, intestinal diseases can interfere with the absorption of antioxidants and fatty acids in the small intestine. And disturbances to the gut microbiota can limit the fermentation of fiber in the hindgut, therefore limiting the energy needed for reproduction. (Feary et al., 2006)

Sperm Quality

Stallion fertility ultimately relies on the quality of sperm produced by the stallion. High-quality sperm has high motility and concentration. Sperm motility refers to the ability of sperm to move efficiently through the mare’s digestive tract to fertilize an egg, while sperm concentration describes the density of sperm in semen. (Varner et al., 2014)

Stallions with good sperm motility and concentration have increased pregnancy rates, so promoting the production of quality sperm is vital for supporting stallion fertility. Although genetics plays a role in these characteristics, all the above factors can also influence sperm quality and stallion fertility.

Gut Health Drives Stallion Fertility

The many factors that can influence stallion fertility (stress, body condition, nutrition, gi tract health and sperm quality) are inter-related, with digestion serving as a link between them. Without a healthy digestive system, stallions can’t benefit from nutrition programs that support optimal body condition and sperm quality. 

It’s important to address every single one of these factors listed above in order to improve fertility, or else the vicious cycle will continue:

  • Stress leads to poor gi tract health, which prevents stallions from getting all the nutrients they need. 
  • Inadequate nutrition leads to poor body condition, which is associated with reduced fertility
  • This lower fertility likely results from poor sperm quality and nutritional deficiencies linked to poor gi tract health.

However, with the right tweaks to your management program (specifically in regards to managing gi tract health), you can turn that vicious cycle into a positive loop:

  • Reduced stress leads to better gi tract health.
  • Good gi tract health allows for better nutrient absorption.
  • Complete nutrition builds good body condition.
  • Good body condition means quality sperm.
  • Quality sperm leads to better breeding outcomes.

How SUCCEED Supports Stallion Fertility

Targeted management that supports optimal digestive health in breeding stallions can help prevent weight loss and nutrient deficiencies during stressful periods. These stallions benefit from additional digestive support that promotes efficient nutrient absorption, which in turn can impact sperm production and reproductive performance.

SUCCEED Digestive Conditioning Program is a patented, nutritional formula that supports a healthy gut in breeding stallions (and all horses). The ingredients in SUCCEED DCP provide beta-glucans, polar lipids, yeast and amino acids that support bioavailability, nutrient absorption, a healthy gut lining, mucus production, balanced, hindgut, and much more. 


  1. Aurich, J. et al. Effects of season, age, sex, and housing on salivary cortisol concentrations in horses. Domest Anim Endocrinol. 2015.
  2. Malmkvist, J. et al. Behavior and stress responses in horses with gastric ulceration. Appl Anim Behav Sci. 2012.
  3. Manyovani, R. et al. Energy and protein allowances and requirements in stallions during the breeding season, comparing different nutritional systems. J Anim Sci. 2011.
  4. Hurtgen, J. Evaluation of the Stallion for Breeding Soundness. Vet Clin North Am Equine Pract. 1992.
  5. Bazzano, M. et al. Use of nutraceuticals in the stallion: Effects on semen quality and preservation. Reprod Domest Anim. 2021.
  6. Brinsko, S. et al. Effect of feeding a DHA-enriched nutraceutical on the quality of fresh, cooled, and frozen stallion semen. Theriogenology. 2005.
  7. Morte, M. et al. The quantification of lipid and protein oxidation in stallion spermatozoa and seminal plasma: Seasonal distinctions and correlations with DNA strand breaks, classical seminal parameters and stallion fertility. Anim Reprod Sci. 2008.
  8. Feary, D. et al. Enteritis and Colitis in Horses. Vet Clin Equine Pract. 2006.
  9. Varner, D. et al. Stallion fertility: A focus on the spermatozoon. Equine Vet J. 2014.



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