By: Dr Rosie Alcorn BVSc PG Cert VPS Cert AVP MRCVS
As we head into winter, many breeding stallions are enjoying a well-earned break from covering mares. For most, this period allows them to regain condition lost during the busy breeding months and to recharge mentally and physically. Others may still be competing or undergoing semen collection for freezing.
The aim during the off-season is to maintain a healthy body condition and optimise fertility for the year ahead. Even when resting, stallions have roughly 10% higher energy requirements than mares or geldings due to their metabolism and ongoing reproductive activity. High-quality forage should form the foundation of the diet, supported by an appropriate balancer or concentrate to meet remaining nutritional needs.
Maintaining an appropriate BCS is essential. Obesity is associated with poorer fertility and reduced semen quality. Although equine-specific research is limited, studies in other species strongly support this link.
For most stallions, a BCS of 3 out of 5 is ideal heading into the breeding season.
Stallions that tend to lose weight easily or face a particularly demanding season may benefit from starting slightly higher, at 3.5 out of 5.
Fatty acids are vital components of cell membranes, and sperm cells contain significantly higher concentrations of essential fatty acids than most other tissues. Sperm must maintain structural integrity despite exposure to oxidative stress, temperature fluctuations, and mechanical pressures during transport or freezing.
Supplementing omega-3 fatty acids, particularly EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), has been shown to:
Improve sperm membrane stability, increasing cell resilience
Enhance motility and progressive movement
Improve concentration and morphology, supporting overall fertility
Reduce oxidative damage, preserving semen quality
Improve the sperm’s ability to withstand chilling, freezing, and thawing - essential for chilled and frozen semen programmes
These benefits make omega-3s one of the most valuable nutritional additions during the off-season.
Marine-derived oils (fish or algae) provide EPA and DHA in their active forms and are the most effective source for fertility support.
Plant-based oils (e.g., linseed/flax) contain ALA, which horses convert to EPA and DHA at very low efficiency - often less than 10%.
For stallions intended for active breeding programmes, marine-derived omega-3 sources are preferred.
Protein quality is just as important as quantity. Stallions require high-quality protein to maintain body tissues and support sperm production.
Nurture and Nurture Pro are both high in quality proteins (15.5% and 30%) and low in sugar and starch. As well as this, added DHA omega 3 shows to support semen motility.
Essential amino acids cannot be synthesised in sufficient amounts by the horse and must be supplied through the diet. For stallions, the most important include:
Lysine: the primary limiting amino acid, required in higher amounts for breeding stallions
Methionine: supports reproductive tissues and contributes to hoof and coat health
Threonine: important for immune function and protein synthesis
A shortage of these key amino acids may limit the stallion’s ability to produce healthy sperm cells, even if overall protein intake appears adequate.
The off-season is an ideal time to rebuild muscle and tissues lost during the breeding season. Using protein sources with high amino acid availability ensures the stallion receives the building blocks required for recovery and fertility.
Micronutrients play key roles in supporting fertility:
Vitamin E: a vital antioxidant essential for testicular health
Selenium: works synergistically with Vitamin E - care must be taken to avoid over supplementation
Zinc, copper, manganese: support hormone production and reproductive tissue integrity
A high-quality balancer helps ensure accurate and safe micronutrient intake.
Healthy digestion supports nutrient absorption, condition, and overall wellbeing:
Provide ample high-quality forage
Consider prebiotics or probiotics during dietary changes
Avoid high-starch feeds to reduce digestive stress
Recent research is also exploring the behavioural benefits of feeding stallions high-fat, low-starch diets.
Changes to the diet can take up to three months to show measurable improvements in semen quality. This makes the off-season a critical preparation period. Establishing good nutrition now helps ensure the stallion enters the breeding season with:
Correct body condition
High-quality semen
Healthy digestion
Reduced stress
Improved resilience
By optimising out-of-season nutrition and management, you give your stallion the best chance of performing at his peak when the breeding season begins.
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