Influencia del tiempo de descongelación en la motilidad, viabilidad y estructura del acrosoma en espermatozoides de toros Bos indicus

Bovine semen cryopreservation is a strategic tool for artificial insemination; however, its effectiveness depends largely on the thawing protocol, since thermal exposure can intensify cryogenic damage to sperm membranes and the acrosome. The objective of this study was to evaluate the effect of three thawing times in a 37 °C water bath T1 (35 s), T2 (50 s), and T3 (65 s) on the functional and structural quality of preserved semen from Bos indicus bulls, using motility, sperm kinematics, and cell integrity as response parameters. A completely randomized design with three replicates per treatment was applied; motility and kinematic variables were measured using a computer-assisted sperm analysis system (CASA), and integrity was assessed by Eosin–Nigrosin staining (viability and plasma membrane integrity) and Giemsa staining (acrosomal status). Total motility was higher in T1 (45.03%) compared with T2 (40.84%) and T3 (43.14%), while progressive motility remained similar among treatments; in contrast, linearity increased from 0.41 to 0.52 and straightness from 0.77 to 0.86 as exposure time increased. However, viability decreased markedly from 44.56% (T1) to 16.49% (T2) and 8.59% (T3), with mortality reaching 91.41% in T3, and the proportion of sperm with intact acrosomes declined from 53.66% (T1) to 16.33% (T3). It is concluded that, although longer thawing times promote straighter trajectories, they severely compromise sperm integrity; therefore, 35 s at 37 °C provides the best operational balance to preserve fertilizing potential within the evaluated range.