Sperm DNA damage in relation to lipid peroxidation following freezing-thawing of boar semen

This study investigated the relationships between lipid peroxidation (LPO) and sperm DNA damage following freezing-thawing of boar semen in different extenders. The comet assay was used to measure the extent of sperm DNA damage in a cryoprotectant-free extender or in cryoprotectant-based extenders after single and repeated freezing and thawing. As well as an analysis of sperm motion characteristics, mitochondrial function, membrane integrity, and lipid peroxidation (LPO) were assessed simultaneously with the measurements of sperm DNA damage. Consistent positive significant correlations were found between sperm DNA damage and LPO after freezing-thawing. Comet assay measurements showed that cryo-induced sperm DNA damage was more marked in the cryoprotectant-free extender, irrespective of freezing cycle. The frequency of sperm cells with damaged DNA increased with repeated freezing and thawing in the cryoprotectant-based extenders. Except for sperm DNA damage, there were no consistent associations between post-thaw sperm LPO and sperm quality characteristics. It could be suggested that the increased LPO of membrane phospholipids is associated with higher susceptibility of boar spermatozoa to cryo-induced DNA damage.Keywords: Comet assay measurements, cryopreservation, extenders, spermatozo

DGAT1 p.K232A polymorphism in dairy and dual purpose Italian cattle breeds

The aim of this study was to evaluate the allele frequency distribution at the DGAT1 p.K232A polymorphic site in seven Italian dairy and dual purpose cattle breeds. On the whole, 651 animals belonging Italian Holstein (116), Italian Brown (105), Italian Simmental (95), Valdostana Red Pied (95), Rendena (62), Reggiana (128) and Modenese (50) were genotyped by PCR-RFLP. Sequencing was carried out to confirm results of the genotyping protocol. The DGAT1 p.232K allele was identified in Italian Holstein (25.4%), Reggiana (17.2%), and with very low frequency in Italian Simmental, Valdostana Red Pied and Rendena (1%). In Italian Brown and Modenese, this allele was not detected. These results indicated that this polymorphic site can be considered for association studies only in Italian Holstein and Reggiana breeds. Deviation from Hardy-Weinberg equilibrium was observed in the Reggiana breed (P<0.01) in which there was an excess of heterozygous sires and absence of animals with the p.232KK genotype. This result should be further evaluated because the analysed sires represented almost all bulls available for artificial insemination in this breed. Comparison of allele frequencies at the DGAT1 locus with several other Holstein populations showed a wide range of variability, probably due to different selection strategies adopted