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Abstract: Cryopreserved straws of semen (n =228) from Holstein bulls (n =47) were examined for bacterial presence and sperm DNA fragmentation (SDF) dynamics. Commercial semen doses (representing six ejaculates per individual) were randomly selected from a bull stud in Spain. The dynamics of SDF were assessed after thawing (T0) and at 4, 24, 48, 72 and 96h of incubation at 37°C, using the commercial variant of the sperm chromatin dispersion test for Bovine (Halomax®). One group of bulls showed a bacterial presence in semen samples between 0 and 96h of incubation (n =23, group A) while the other did not (n =24, group B). Immediate post-thaw differences in SDF were not observed when both groups were compared. However, the rate of increase in SDF (rSDF) over time, considered as an estimate of the kinetic behaviour of sperm DNA survival, was significantly higher (P <0.05) in semen samples from group A (0.7% per hour) versus group B (0.05% per hour). Polymerase Chain Reaction (PCR) assay was used for DNA amplification using primers designed for specific regions of the bacterial gene that codifies for 16S rRNA. Different species within the phyla Bacteroidetes, Firmicutes, Proteobacteria, Cyanobacteria, Fusobacteria and Actinobacteria were identified. The results show that (1) SDF at baseline (T0) may not be affected by the presence of bacteria but the rSDF can increase due to bacterial growth during incubation, (2) the increase in the rSDF is characteristic of some bulls but not for others, and (3) certain bacterial strains are repeatedly found in separate ejaculates from the same bull. [Copyright &y& Elsevier]

Abstract: This study examined the dynamic response of Spermatozoa DNA Fragmentation after sex selection in bulls using a MoFlo® SX (Beckman Coulter, Miami FL) spermatozoa sorter. The dynamic response of spermatozoa DNA fragmentation refers to the changing values of SDF, i.e., rate of SDF (rSDF), when analyzed periodically over a set incubation time at 37 °C. A dynamic assessment of SDF using non-sorted and sex-sorted spermatozoa samples during 72 h of incubation at 37 °C was performed. Results showed a reduced DNA longevity in sex-sorted frozen-thawed spermatozoa, with spermatozoa DNA damage appearing between 24 h and 48 h. The baseline SDF level was higher in conventional frozen-thawed than in sex-sorted frozen-thawed spermatozoa samples; while the reverse occurred for the rSDF. The afore-mentioned result produced a crossover point between both dynamic tendencies of SDF for sex-sorted versus conventional samples. We defined this crossover point as the Crossover Positioning Time (CPT) or the time (in hours) where both curves crossover after a period of spermatozoa incubation at 37 °C. The point at which the CPT occurs could be used as an indicator of the rSDF for individual bulls after X- and Y-chromosome bearing spermatozoa selection. CPT values produced a window of SDF ranging between 24 h and 48 h in the present experiment. It is proposed that higher values for CPT are indicative of bulls presenting chromatin that is more resistant to the external stressors affecting spermatozoa DNA after spermatozoa sorting. [Copyright &y& Elsevier]

Abstract: This study examined the static response of Spermatozoa DNA Fragmentation (SDF) after sex selection in bulls using a MoFlo® SX (Beckman Coulter, Miami FL) spermatozoa sorter to produce three different subpopulations: 1) Spermatozoa bearing X- chromosomes with a purity of 95%, 2) Spermatozoa bearing Y-chromosomes with a purity of 95%, and 3) non-viable spermatozoa. The static response of SDF refers to the baseline values observed for DNA damage when analyzed pre- and post sex-sorting. Results showed that while the baseline level SDF in pre-sorted bull spermatozoa samples ranged from 5.3% to 11% with an average of 7.9% ± 2.1%, the level of SDF obtained in X- and Y-chromosome sorted samples was much lower (3.1% ± 1.9%) and statistical differences were obtained after comparing both groups (P < 0.01). Spermatozoa containing a fragmented DNA molecule tend to be accumulated in the non-viable subpopulation. The baseline SDF level in X- and Y-chromosome sorted subpopulations is reduced, by 63% on average when compared to the values obtained in the neat semen sample. Different bulls exhibit unique SDF reduction efficiencies via the X- and Y-chromosome sex selection process. [Copyright &y& Elsevier]