Post-thaw sperm morphokinetics and mitochondrial genes profile of buck semen supplemented with selenium in two different forms

Background
The quality characteristics of semen is a determinant factor for improving fertility of rabbit.
Objectives
The current investigation was done to evaluate post-thaw sperm morphokinetics and mitochondrial genes expression profile of buck semen supplemented with selenium in two different forms.
Materials and methods
Sexually mature bucks (n=16) that aged three months on average were used for collecting two ejaculates which were evaluated using computer assisted semen analysis (CASA) program. The semen samples of all experimental animals which recorded progressive motility greater than or equal to 70% were pooled for cryopreservation. The pooled semen was divided into three groups that were supplemented with selenium nanoparticles and selenium in normal form in addition to the control group. Morphological characteristics as well as CASA parameters were assessed after freezing for 1 week. Moreover, enzymatic activity assays were performed to measure the antioxidant capacity of cryopreserved buck semen. Transcriptional profile of mitochondrial activity and antioxidant defense regulating genes was conducted using quantitative real-time polymerase chain reaction (PCR).
Results and conclusion
The addition of selenium in normal and Nano forms has significantly (P ≤0.05) enhanced some of CASA parameters such as DCL (µm), DAP (µm), DSL (µm), VCL (µm/s), VAP (µm/s), Amplitude of lateral head (ALH) (µ), BCF (Hz), and VSL (µm/s) during prefreezing period compared with control group. Moreover, the data presented in the present study indicated a significant (P ≤0.05) improvement of post-thaw total and progressive sperm motility in the two groups supplemented with normal and Nano compared with control group. The post-thaw level of total antioxidant capacity (TAC) and percentage of live sperm were higher in the two groups supplemented with selenium and Nano selenium than the control group. The expression profile of candidate genes regulating mitochondrial activity (ATP Synthase F1 Subunit Alpha (ATP5A1), NADH dehydrogenase subunit1 (ND1), NADH dehydrogenase subunit2 (ND2), and Carnitine palmitoyltransferase (CPT2)) was increased significantly (P ≤0.05) in semen supplemented with selenium in normal and Nano forms compared with the control group. In conclusion, the data of this investigation demonstrated enhancement of CASA parameters during pre-freezing post thaw total and progressive sperm motility in the two groups supplemented with normal and nano selenium. The proportion of sperm viability and the level of total antioxidant capacity were enhanced in the two groups supplemented with selenium which was coupled with up-regulation of mitochondrial transcripts. It seems the both two forms shared the same mechanism on improving post-thaw physical and molecular qualities of rabbit sperm.