Urolithin A mitigates cryopreservation-induced oxidative damage and improves sperm quality and fertilizing ability in Turkey semen

Turkey spermatozoa are highly susceptible to cryoinjury, and post-thaw fertility with frozen-thawed semen frequently remains below 40%. Urolithin A (UA), a gut microbiota-derived ellagitannin metabolite with mitophagy-inducing and antioxidant properties, improves sperm quality in other species, but its efficacy in avian semen cryopreservation has not been tested. Pooled semen samples from adult Bronze turkeys ( n = 7 independent pools) were extended in a glucose-based diluent supplemented with 0 (control), 1, 5, or 10 µM UA and cryopreserved by the vapor-freezing method. Post-thaw evaluations included computer-assisted sperm analysis (CASA), sperm viability, plasma membrane functionality, DNA integrity, and oxidative stress/antioxidant biomarkers (TAC, SOD, GPx, MDA), together with fertility and hatchability following artificial insemination of turkey hens. Supplementation with 1 µM and 5 µM UA significantly improved total motility (58.4 ± 0.82% and 56.7 ± 0.91%, respectively) and progressive motility and most velocity parameters relative to control and 10 µM UA. Sperm viability, plasma membrane functionality and DNA integrity were likewise higher in the 1 and 5 µM groups, and TAC, SOD and GPx activities were elevated while MDA was reduced, indicating mitigation of oxidative stress. The 10 µM dose provided little or no additional benefit and for some parameters showed values similar to or worse than the control, consistent with a non-monotonic dose–response. Fertility and hatchability were significantly higher in the 1 µM (71.7% fertility, 54.8% hatchability) and 5 µM groups than in the frozen control. These findings indicate that low micromolar concentrations of UA, particularly in the range of 1–5 µM, protect turkey spermatozoa against cryopreservation-induced oxidative damage and improve in vivo fertilizing potential, consistent with the mitochondria-protective mode of action reported for UA in mammalian species. Urolithin A is a promising natural additive for avian semen cryopreservation and germplasm banking.