Can the Quality of Semen Affect the Fertilisation Indices of Turkey Eggs?

Several factors, including semen quality, can influence fertilisation success. Poor semen parameters may necessitate more frequent inseminations or the removal of males with consistently low fertility. This study evaluated turkey ejaculates (n = 37) with good fertility (GF) and impaired fertility (IF). The analyses included sperm motility parameters (total motility—TMOT, progressive motility—PMOT, curvilinear velocity—VCL, straight-line velocity—VSL, average path velocity—VAP, linearity—LIN, straightness—STR, amplitude of lateral head displacement—ALH, and beat cross frequency—BCF), plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), and nitric oxide (NO) production, as well as enzymatic and biochemical assays of semen, such as superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) activities, glutathione (GSH) content, malondialdehyde (MDA) levels, and zinc (Zn2+) concentration. In parallel, the proteomes of seminal plasma and spermatozoa were separated using SDS- and Tricine-PAGE, and selected proteins were identified by nano LC-MS/MS. Spermatozoa derived from IF ejaculates exhibited significantly reduced TMOT (p = 0.002), VCL (p = 0.028), and PMI (p = 0.000), accompanied by elevated STR (p = 0.000) and NO production (p = 0.044). In the seminal plasma of IF males, a significant decrease was noted in SOD (p = 0.000) and GPx (p = 0.001) activities, whereas CAT activity was markedly higher (p = 0.014). Seminal fluid from IF ejaculates was also characterised by increased GSH (p = 0.014) and MDA (p = 0.014) concentrations, accompanied by reduced Zn2+ content (p = 0.014). In contrast, IF spermatozoa exhibited elevated SOD activity (p = 0.001), but reduced GPx (p = 0.000) and CAT (p = 0.012) activities. Sperm cells from IF ejaculates also had lower GSH levels (p = 0.000), higher MDA concentrations (p = 0.000), and increased Zn2+ content (p = 0.018) compared with those from GF ejaculates. A proteomic analysis revealed differences in fertility-associated proteins: peroxiredoxin 6 (PRDX6) was detected exclusively in GF semen, whereas alpha-enolase (ENO1), fatty acid-binding protein (FABP7), cytoplasmic aspartate aminotransferase (GOT1), and L-lactate dehydrogenase B (LDHB) were detected only in IF semen. Overall, the results demonstrate that both semen parameters and proteome composition may potentially affect the fertilisation outcomes in turkeys.