Cryopreservation and quality assessment of boar semen collected from bulk samples

The purpose of this study was to examine sperm quality after cryopreservation of ejaculates collected as a bulk sample, which is routinely part of semen collection, and to compare this quality with the sperm-rich fraction in boars. Ejaculates were collected as sperm-rich fractions (SRF) and bulk samples (BE) using a gloved-hand technique. Fresh semen quality in terms of semen volume, sperm concentration, total sperm motility and pH were conventionally evaluated. Then, semen was cryopreserved using the liquid nitrogen vapour method. The post-thaw sperm quality was evaluated by assessing sperm motility, live sperm with normal apical ridge and high mitochondrial energy status, lipid peroxidation was evaluated using CASA and fluorescent multiple staining and MDA levels were determined using a spectrophotometer, respectively. In terms of fresh semen quality, sperm motility in fresh semen did not differ significantly between the two groups. The treatment with the greater mean volume (BE; P < 0.05) had a lower mean sperm concentration (P < 0.05); meanwhile, the mean ejaculate pH collected as BE was more basic compared with SRF (P < 0.05). However, there were no significant post-thaw quality changes between sperm-rich fractions and bulk samples of semen. In conclusion, ejaculates can be collected as bulk samples without the need to classify fractions for boar semen cryopreservation.