PS8-25. Effect of Rumen-protected Methionine Supplementation on Antioxidant Status and Sperm Kinematic Properties in Angus Beef Bulls.

Abstract Antioxidant metabolism is essential for cellular survival. Antioxidant molecules delay or prevent oxidative damage caused by free radicals during oxidative stress. Sperm cells are particularly susceptible to oxidative stress due to limited cellular repair systems and reduced antioxidant defenses associated with minimal cytoplasmic content. Methionine is an essential sulfur-containing amino acid whose biochemical properties allow it to play key roles in several biological processes, including antioxidant activity. This study aimed to evaluate the effect of rumen-protected methionine (RPM) supplementation on oxidative stress and sperm kinematic properties in bulls. Eighteen Angus beef bulls (body weight = 700 ± 21 kg) were used in an 84-day experiment. Bulls were assigned to one of two treatments: a maintenance diet (CON; n = 9) or the maintenance diet supplemented with RPM at 0.08% of dry matter (n = 9). Semen samples were collected on day 84 and sperm kinematics evaluated using computer-assisted sperm analysis (CASA). Serum samples were collected on days 0 and 84 and seminal plasma (SP) samples were collected on days 0, 42, and 84 for glutathione peroxidase (GP) analysis. Data were analyzed using the MIXED procedure of SAS, with significance considered when P ≤ 0.05, and tendencies when 0.05 ≤ P ≥ 0.10. Though serum GP concentrations were not impacted (96.1 vs. 83.3 ± 8.3 μ/mL for CON and RPM, respectively), concentrations of GP in seminal plasma tended (P = 0.08) to be greater in bulls fed RPM (75.0 vs. 113.3 ± 14.5 μ/mL for CON and RPM, respectively). Sperm kinematic properties were affected by methionine supplementation. In sperm classified as motile, bulls receiving RPM exhibited greater (P < 0.0001) curvilinear velocity (VCL) (230.8 vs. 202.8 ± 9.0 μm/s) and average path velocity (VAP; 131.8 vs. 119.5 ± 3.2 μm/s; P = 0.01) compared to the CON group, however, there was no effect on straight-line velocity (VSL; P ≥ 0.44). In populations of sperm classified as progressively motile, greater VCL (229.0 vs. 237.2 ± 8.4 μm/s; P < 0.001) and VAP (144.4 vs. 146.6 ± 3.5 μm/s; P < 0.0001) were observed in the RPM compared to CON, but there was no effect on VSL (P ≥ 0.83). Furthermore, in populations of slow sperm, the VCL was greater (64.0 vs. 99.01 ± 13.8 μm/s; P = 0.001) and VAP tended (P ≥ 0.06) to be greater in RPM compared with CON (27.3 vs. 44.4 ± 6.0 μm/s for CON and RPM, respectively), however, there was no effect on VSL (P ≥ 0.14). Overall, supplementation with rumen-protected methionine did not impact serum glutathione peroxidase activity, but tended to impact glutathione peroxidase activity in seminal plasma and improved sperm kinematic properties in beef bulls.