Effects of hemp-based polyunsaturated fatty acid supplementation on membrane lipid profiles and reproductive performance in Martina Franca jacks

In response to the growing demand for sustainable livestock production, this study represents the first investigation into the effects of dietary hemp oil supplementation—rich in polyunsaturated fatty acids (PUFAs)—on the reproductive performance and membrane lipid composition of Martina Franca donkey stallions. Twelve adult jacks were divided into control and treatment groups, with the latter receiving an isoproteic diet enriched with hemp oil for 90 days. Throughout the trial, semen quality parameters (volume, concentration, motility, morphology) and lipid profiles of both spermatozoa and erythrocyte membranes were assessed, alongside correlations with dietary fatty acid intake. The supplementation significantly influenced the membrane composition of both sperm and erythrocytes, leading to increased incorporation of omega-3 fatty acids, especially eicosapentaenoic acid (EPA), and a reduction in saturated fatty acids (SFAs), resulting in improved membrane fluidity and oxidative stability. While total and gel-free semen volume, as well as sperm concentration, decreased over time, sperm motility and the percentage of morphologically normal spermatozoa improved. These changes were accompanied by a significant reduction in the peroxidation index, suggesting enhanced antioxidant protection. Correlational analysis revealed that a more favorable ω3/(ω3 + ω6) balance in the diet was positively associated with improved sperm membrane quality and overall semen traits. The lipidomic changes observed indicate that dietary PUFAs were successfully integrated into cellular structures, highlighting their functional role in sperm viability, membrane fluidity, and resistance to oxidative stress. Given that equids cannot synthesize essential PUFAs endogenously, such dietary interventions could be critical in managing fertility in breeding programs. In conclusion, hemp oil supplementation may offer a viable, sustainable strategy to enhance male reproductive efficiency in donkeys, with potential benefits for the conservation of autochthonous breeds and the long-term viability of donkey dairy farming systems