Influence of cryoprotectants glycerol and amides, combined with antioxidants on quality of frozen-thawed boar sperm

The present study was undertaken to examine whether the cooling and freezing extenders containing a mixture of antioxidants (AOs) catalase, Na-pyruvate and mercaptoethanol and one of three types of cryoprotectants (CPs) would be able to improve the quality of frozen-thawed boar sperm. The collected semen, only the sperm-rich fraction, was diluted 1:1 with Androhep plus™ extender, stored at 15 °C for 2 h and centrifuged. The centrifuged sperm pellet was re-suspended in lactose-egg yolk extender and divided into four groups for mixing with freezing extenders containing different kinds of CPs at 5 °C: (I) glycerol (GLY) as control; (II) GLY with AOs; (III) dimethyl formamide (DMF) with AOs and (IV) dimethyl acetamide (DMA) with AOs. Processed sperm were packaged in 0.25-mL straws and frozen using a controlled rate freezer. After thawing, the diluted thawed sperm were incubated at 38 °C for 10 min and was assessed for motility by CASA, membrane/acrosome integrity by FITC-PNA/PI and DNA integrity (DFI) by SCSA. All sperm parameters evaluated, except DFI, were negatively affected (P < 0.001) when using DMF (III) or DMA (IV) as CPs instead of GLY (I and II). Total sperm motility was lower (P < 0.001) in the samples supplemented with AOs (32.4 ± 1.2, 23.9 ± 1.5, 6.9 ± 0.7, and 10.3 ± 0.9%, for treatments I, II, III and IV, respectively). The quality of sperm frozen in DMF was not different from DMA (P > 0.05). There was no difference in DFI among the studied groups (P > 0.05). In conclusion, based on the present results, addition of AOs to cooling and freezing extenders and/or replacement of GLY with DMF or DMA could not improve quality of frozen-thawed boar sperm.