Oxidative stress is a major factor adversely affecting semen quality in male rabbits. L-carnitine (LC) is an antioxidant that neutralizes harmful free radicals, protecting cell membranes (particularly mitochondrial membranes) from oxidative stress. This study investigated the effects of dietary LC supplementation (0, 75, 150, 300 and 450mg/kg) on sperm kinematic analysis, antioxidant capacity, membrane integrity, acrosome integrity, mitochondrial membrane potential (MMP) and anti-apoptotic changes in 50 Fujian Yellow male rabbits over an 8-week period. Semen samples were subjected to CASA, conventional assay kit, SYBR14/PI double staining, PNA-FITC/PI double staining, JC-1 assay kit and PE/7-AAD double staining. Finally, the relative expression levels of NRF-2, KEAP-1, Bax, Bcl-2, and caspase-3 in sperm were detected using quantitative real-time polymerase chain reaction (qRT-PCR). The results showed that dietary supplementation of LC at 300mg/kg increased ejaculate volume, sperm concentration, progressive motility and key sperm kinematic parameters including VCL, VAP and ALH (P<0.05). It concurrently increased seminal plasma antioxidant markers (SOD, GSH-Px, T-AOC) and LC content and reduced MDA and ROS levels. It also increased SOD, T-AOC and CAT levels in sperm (P<0.05). Supplementation with LC at 150 and 300mg/kg improved sperm acrosomal and plasma membrane integrity (P<0.05), while supplementation at 450mg/kg reduced early and late apoptosis rates (P<0.05). Furthermore, LC supplementation upregulated Bax mRNA expression, downregulated Bcl-2 mRNA expression, and reduced the Bcl-2/Bax ratio (P<0.05) without affecting caspase-3 expression. Additionally, LC300 specifically increased the expression of NRF-2 and KEAP-1 (P<0.05). Furthermore, LC300 also improved post-thaw sperm progressive motility and velocity parameters including VSL, VAP and ALH (P<0.05). These results suggest that dietary LC supplementation could improve fresh semen quality via antioxidant induction, membrane stabilization and anti-apoptotic effects, and enhanced post-thaw sperm motility.

To Cite This Article: Gao CF, Liu M, Bai LY, Lan YX, Sun SK, Chen DJ, Wang JX, Xie XP and Sang L* 2025. Effect of dietary l-carnitine supplementation on fresh semen characteristics and post-thaw sperm quality in male rabbits. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.281