Optimizing Cryopreservation of Pseudoplatystoma magdaleniatum Semen: Evaluation of Two Permeable and Two Non-Permeable Cryoprotectants

The study aimed to evaluate the effectiveness of the cryopreservation protocols for Pseudoplatystoma magdaleniatum semen using dimethyl sulfoxide (DMSO) or methanol (MET) as permeable cryoprotectants at two concentrations (5% and 10%) combined with 12% egg yolk (Y12%) or 5% skimmed milk powder (SMP5%) and glucose (6%), resulting in eight treatments. A semen pool (n = 8) was diluted in a 1:4 ratio, packed in 2.5 mL straws, and frozen in nitrogen vapors. It was thawed at 35 °C for 90 s. Sperm kinetics and motility duration of fresh, prefrozen, and thawed semen were analyzed using a CASA system. The osmolarity of seminal plasma and cryosolutions was estimated. Fertilization (F) and embryo viability (E) rates of thawed semen were evaluated. The osmolarity of seminal plasma was 251.1 ± 3.3 mOsmol/kg and, in the cryosolutions, ranged between 1248.3 ± 19.9 mOsmol/kg (DMSO5% + Y12%) and 3488.2 ± 1.5 mOsmol/kg (MET10% + Y12%). After thawing, total motility ranged from 38.2% to 60.5%, representing a significant reduction compared to fresh semen (95.4 ± 2.1%) (p < 0.05). The best fertilization and embryo viability rates of thawed semen were obtained with DMSO5% + SMP 5% (F = 20.7%, E = 11.7%) and MET10% + SMP5% (F = 20.1%, E = 11.5%) (p < 0.05). A cryopreservation protocol for P. magdaleniatum semen with 5%DMSO or 10%MET combined with SMP5% is possible, but further study is necessary to optimize its fertilizing capacity.