The beneficial effect of glycerol as a cryoprotectant, especially for sperm cryopreservation, has been shown in many studies. However, glycerol is toxic to living cells, and boar sperm in particular show greater sensitivity to glycerol than sperm from other domestic animals. Amides have been studied as alternative cryoprotectants for freezing stallion sperm. Sperm frozen in methylformamide or dimethylformamide as cryoprotectants show similar motility when thawed compared with sperm frozen in glycerol. We evaluated the cryoprotective effects of dimethylformamide on boar sperm freezing. To test the effect of amides, the concentration of boar semen was adjusted to , and seminal plasma was removed using Hulsen solution. After centrifugation, the pellet was diluted in modified-Modena B extender. Lactose-egg yolk (LEY) extender was used as the cooling extender. The freezing extender was madeed aaddition of the optimal amount of glycerol and amides to LEY-Glycerol-Orvus ES Paste extender, and this extender was used for the second dilution. Diluted sperm were frozen in liquid nitrogen using the 0.5 mL straw method. Sperm frozen in extender with glycerol as a cderol were compared with those frozen in extender including the different amides. Sperm were tested for motility, viability, the sperm chromatin structure assay, and normal apical ridge after thawing. The percent of motile sperm diluted in glycerol was as high as that in the stallion study (61%). Dimethylformamide showed positive effects on sperm quality and was better than glycerol. Methylformamide provided similar sperm quality as glycerol. Therefore, dimethylformamide is useful for reducing cryoinjury in boar sperm and is expected to be useful as an alternative cryoprotectant.

Sex-sorting of sperm is an assisted reproductive technology (ART) used by the livestock industry for the mass production of animals of a desired sex. The standard method for sorting sperm is the detection of DNA content differences between X and Y chromosome-bearing sperm by flow cytometry. However, this method has variable efficiency and therefore requires verification by a second method. We have developed a sex determination method based on quantitative real-time polymerase chain reaction (qPCR) of the porcine amelogenin (AMEL) gene. The AMEL gene is present on both the X and the Y chromosome, but the length and sequence of its noncoding regions differ between the X and Y chromosomes. By measuring the threshold cycle (Ct) of qPCR, we were able to calculate the relative frequency of X chromosome. Two sets of AMEL primers were used in these studies. One set (AME) targeted AMEL gene sequences present in both X and Y chromosome, but produced PCR products of different lengths for each chromosome. The other set (AXR) bound to AMEL gene sequences present on the X chromosome but absent esholthe Y-chromosome. Relative product levels were calculated by normalizing the AXR fluorescence to the AME fluorescence. The AMEL method accurately predicted the sex ratios of boar sperm, demonstrating that it has potential value as a sex determination method.