Are Lower Fertilisation Indices of Turkey Eggs Associated with Semen Quality?

Candling is a standard method for assessing egg fertility and embryonic development in poultry. Fertilisation success can be influenced by several factors, including semen quality. 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, 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. The findings suggest that IF ejaculates exhibit insufficient extracellular antioxidant capacity to neutralise reactive oxygen species (ROS). Elevated antioxidant enzyme activity, reduced GSH levels, and increased MDA concentrations indicate the presence of oxidative stress in spermatozoa. A proteomic analysis revealed differences in fertility-associated proteins: PRDX6 was detected exclusively in GF semen, whereas ENO1, FABP7, GOT1, and LDHB were unique to IF semen. Overall, the results demonstrate that both semen parameters and proteomic composition may contribute to fertilisation outcomes in turkeys.