Cryopreservation of collared peccary (Pecari tajacu L., 1758) epididymal sperm using extenders based on Tris and powdered coconut water (ACP®-116c)

The aim of this study was to establish a functional freezing-thawing protocol for epididymal sperm of collared peccaries (Pecati tajacu L., 1758) by comparing different extenders. The epididymal sperm from 12 sexually mature males was recovered by retrograde flushing using Tris-based or coconut water-based (ACP (R)-116c) extenders. After initial evaluation, samples were diluted and frozen with the same extenders to which 20% egg yolk and 6% glycerol were added. After 2 weeks, thawing was performed at 37 degrees C/60 s and sperm motility, vigour, morphology, functional membrane integrity, sperm viability, sperm plasma membrane integrity, and a computer-assisted semen analysis (CASA) were assessed. In addition, to evaluate the survival of frozen-thawed sperm, a thermal resistance test (TRT) was executed. Samples preserved using iris were in better condition compared with those preserved using ACP (R), showing higher values for most assessments performed, including CASA and the TRT (P< 0.05). After determining Tris to be the better of the two extenders, additional samples were thawed using different thawing rates (37 degrees C/60 s, 55 degrees C/7 s, 70 degrees C/8 s). Sperm thawed at 37 degrees C/60 s had the greatest preservation (P< 0.05) of viability (54.1 +/- 5.9%) and functional membrane integrity (43.2 +/- 5.4%), and had higher values for various CASA parameters. In conclusion, we suggest the use of a Tris-based extender added to egg yolk and glycerol for the cryopreservation of epididymal sperm obtained from collared peccaries. In order to achieve better post-thawing sperm quality, we suggest that samples should be thawed at 37 degrees C/60 s.