Cryopreservation of boar sperm: Challenges, improvements, and applications for sustainable swine reproduction

The use of frozen-thawed (FT) boar sperm is essential for the swine industry, as it provides global access to superior genetics, thereby increasing efficiency and profitability. However, the cryopreservation process causes cellular damage, reducing post-thaw sperm quality and fertility, and often resulting in smaller litter sizes. This study evaluated the protective effect of conjugated linoleic acid (CLA; 10 trans, 12 cis-CLA) in freezing extenders on boar sperm quality and in vivo fertility. Semen from three boars was cryopreserved in two groups: a control and a CLA-supplemented group. Post-thaw sperm quality, including membrane stability and acrosomal integrity, was assessed using flow cytometry. Fertility was tested by inseminating 24 sows with either fresh or frozen-thawed semen, recording pregnancy rates and litter sizes. CLA supplementation significantly improved post-thaw sperm membrane integrity and acrosomal preservation, indicating enhanced resilience to osmotic and oxidative stresses. Notably, sows inseminated with CLA-treated semen showed increased total and live-born litter sizes. These findings suggest that CLA acts as a potent cryoprotective additive, likely by stabilising the sperm plasma membrane and mitigating lipid peroxidation. CLA appears to be a promising agent for improving swine artificial insemination programs; however, large-scale studies are still required to confirm its efficacy under commercial conditions.