Bacteriospermia and Sperm Quality of Cryopreserved Bull Semen Used in Artificial Insemination of Cows in South Wollo Zone, Ethiopia

Bacterial DNase activity as a putative inductor of sperm DNA fragmentation in infected bull frozen-thawed semen samples

The aim of this study was to investigate the relationship between DNase activity associated with bacterial contamination of incubated bovine frozen-thawed spermatozoa and elevated sperm DNA fragmentation. Electrophoresis analysis of plasmid PBR322 incubated for 30 min at 37 °C with the supernatant of the diluent of frozen-thawed centrifuged bovine semen straws infected with bacteria showed clear evidence of DNase activity when compared to plasmid incubated in similarly prepared non-infected bovine diluent supernatant (Experiment 1). This DNase activity was subsequently found to be time dependent (0-60 min) and its activity prevented in the presence of EDTA (10 and 20 mM; Experiment 2). Semen straws infected (n = 10) and not infected (n = 10) with bacteria where incubated at 37 °C for up to 48h post-thaw. Semen infected with bacteria showed an exponential increase in bacterial growth and a corresponding increase in sperm DNA fragmentation. Non-infected semen samples showed no change in the incidence of sperm DNA fragmentation over the same period of incubation (Experiment 3). Our experiments reinforce the idea that exogenous DNases present in the semen should be considered as one of the primary contributing causes of sperm DNA fragmentation post ejaculation. In the case of the bull, post-thaw incubation of commercial straws contaminated with bacteria, resulted in increased levels of sperm DNA fragmentation, most likely associated with DNase activity (potentially restriction endonucleases) derived from the bacteria. Such adverse changes in sperm DNA fragmentation, as described here in vitro, may be also operative after insemination in the female reproductive tract (in vivo) and highlight the importance of implementing high levels of hygiene practice during semen processing, especially in light of future trends of bacterial resistance to the common antibiotics used in semen diluents.

Comparative ejaculatory response, fresh and frozen semen quality and fertility to artificial vagina vs electroejaculation method of semen collection in mithun (Bos frontalis) bulls

The study aimed to describe a comparative ejaculatory response, fresh and frozen-thawed semen quality and fertility of semen collected by artificial vagina and electroejaculation in mithun. Experimental bulls were divided into two groups, G-I: young bulls (n = 4; 4-5 years of age) and G-II: older bulls (n = 4; 8-10 years of age). Sixteen ejaculates were collected from each group G-I (AV₁ ) and G-II (AV₂ ) by artificial vagina method (control). Thirty-six ejaculates were collected from the same bulls from each group G-I (EE₁ ) and G-II (EE₂ ) by electroejaculation method (treatment). The study did not reveal any significant (p > 0.05) difference in the ejaculatory responses between EE₁ and EE₂ . Mann-Whitney U test indicated that salivation discomfort sign score was significantly (p < 0.05) higher in EE₁ . Fresh and frozen-thawed semen quality parameters, and motility and velocity profiles recorded by computer-assisted sperm analyser were significantly (p < 0.05) lower in electroejaculation than the artificial vagina. The conception rates (AV₁ vs EE₁ & AV₂ vs EE₂ ) at day 35-45 post insemination were nonsignificantly higher (p > 0.05) in the artificial vagina group. It concluded that, although artificial vagina method has better semen quality, nevertheless, electroejaculation has the potential for semen collection from free-range mithun bulls to incorporate in assisted reproductive technology procedures.

Identification of Bull Semen Microbiome by 16S Sequencing and Possible Relationships with Fertility

Reports on the use of 16S sequencing for the identification of bacteria in healthy animals are lacking. Bacterial contamination of bull semen can have a negative effect on the sperm quality. The aims of this study were threefold: to identify bacteria in the semen of healthy bulls using 16S sequencing; to investigate the differences in the bacterial community between individual bulls; and to establish if there was a relationship between the bacteria isolated and bull fertility. Semen from 18 bulls of known fertility was used for the DNA extraction and 16S sequencing; 107 bacterial genera were identified. The differences in the amplicon sequence variants (ASVs) and the numbers of genera between bulls were noted. Negative correlations (p < 0.05) between several bacterial genera with Curvibacter, Rikenellaceae RC9-gut-group and Dyella spp. were seen. Other negatively correlated bacteria were Cutibacterium, Ruminococcaceae UCG-005, Ruminococcaceae UCG-010 and Staphylococcus, all within the top 20 genera. Two genera, W5053 and Lawsonella, were enriched in bulls of low fertility; this is the first time that these bacteria have been reported in bull semen samples. The majority of the bacteria were environmental organisms or were species originating from the mucous membranes of animals and humans. The results of this study indicate that differences in the seminal microbiota of healthy bulls occur and might be correlated with fertility.

Core Microbiome of Slovak Holstein Friesian Breeding Bulls' Semen

Simple Summary

The aim of this study was to characterize the bacterial profile of semen collected from Holstein Friesian breeding bulls via a high-throughput sequencing approach for a 16S rRNA gene variability analysis. A total of 55 fresh semen samples of sexually mature breeding bulls were used in the study. They were gathered from Holstein Friesian breeding bulls at Slovak Biological Services in Nitra, Slovak Republic. To amplify the V4 region of the 16S rRNA bacterial gene, universal primers 515F and 806R enhanced by a 6 bp barcode identification sequence were used. The 16S rRNA high-throughput sequencing strategy was used. Two microbial clusters were identified among the analyzed samples—the first cluster was based on Actinobacteria and Firmicutes, while the second cluster contained a high prevalence of Fusobacteria.

Abstract

Bacterial contamination of semen is an important factor connected to the health status of bulls that may significantly affect semen quality for artificial insemination. Moreover, some important bovine diseases may be transmitted through semen. Up to now, only a very limited number of complex studies describing the semen microbiome of bulls have been published, as many bacteria are hard to cultivate using traditional techniques. The 16S rRNA high-throughput sequencing strategy allows for the reliable identification of bacterial profiles of bovine semen together with the detection of noncultivable bacterial species. Fresh samples from Holstein Friesian breeding bulls (n = 55) were examined for the natural variability in the present bacteria. Semen doses were selected randomly from Slovak Biological Services in Nitra, Slovak Republic. The most predominant phyla within the whole dataset were Firmicutes (31%), Proteobacteria (22%), Fusobacteria (18%), Actinobacteria (13%) and Bacteroidetes (12%). Samples of semen were divided into two separate clusters according to their microbiome compositions using a cording partition around a medoids analysis. Microbiomes of the first cluster (CL1) of samples (n = 20) were based on Actinobacteria (CL1 average = 25%; CL = 28%) and Firmicutes (CL1 = 38%; CL2 = 27%), while the second cluster (CL2; n = 35) contained samples characterized by a high prevalence of Fusobacteria (CL1 = 4%; CL2 = 26%). Some important indicator microbial groups were differentially distributed between the clusters.

Effects of Extender Type, Storage Time, and Temperature on Bull Semen Parameters

Seminal parameters can be evaluated in situ, or samples can be delivered to a diagnostic centre. How storage conditions affect ejaculates up to evaluation is unclear. We assessed, in 25 commercial bulls electroejaculated in the field, the impact of time until evaluation (0-2 h, 4-6 h, and 24 h post-ejaculation), holding temperature (5 °C vs. room temperature), and extender (AndroMed^®, BIOXcell^® or INRA96^®) on semen quality. Acrosome integrity, sperm viability and morphology, CASA-total and progressive motility, pH, and colony-forming units were assessed. Semen quality was preserved for up to 4-6 h post-ejaculation, except for INRA96^® at 5 °C. Regardless of extender or temperature, motility decreased from 4 to 6 h up to 24 h, with the best values obtained with BIOXcell^® at 5 °C. pH differed from 4 to 6 h up to 24 h, acidifying when stored at room temperature. Microbiological load was stable over time with AndroMed^® and BIOXcell^®, and increased at room temperature with INRA96^®. Our results suggest that AndroMed^® and BIOXcell^® can preserve semen quality for up to 6 h, either at 5 °C or room temperature, while INRA96^® only at room temperature. These results help to fix adequate protocols for short-term storage and shipment of bovine semen collected under field conditions.

Peptide derivatives of dermaseptin S4 in fresh bovine semen for bacterial contamination control: Physicochemical and structural characterization, antibacterial potency, and effects on red blood and sperm cells

The objectives of this study were to examine the physicochemical and structural properties of peptide derivatives of dermaseptin S4, investigate their detrimental effects on red blood and sperm cells and ascertain their antibacterial potency to control bacterial contaminants in fresh bovine semen. The dermaseptin S4 peptide derivatives used in this study were K4S4, S4(5-28), S4(5-28)a, K20S4(5-28), K4S4(1-16)a, K4S4(1-15)a and K4S4(1-15). Peptides K4S4, S4(5-28)a, K20S4(5-28), K4S4(1-15)a and K4S4(1-16)a, with a higher positive charge, were the most potent against the bacterial strains tested, with the lowest minimum inhibitory concentration (MIC), whereas S4(5-28) and K4S4(1-15), with a lower positive charge, showed the highest MIC (p < .01). Haemolysis percentage depended on peptide concentration (p < .01). The K4S4 was the most powerful haemolytic peptide, showing the highest haemolysis percentage at all peptide concentrations (p < .01). In contrast, S4(5-28), S4(5-28)a, K20S4(5-28) and K4S4(1-15) were not able to produce 50% cell lysis up to 100 µM (p < .01). All peptides reduced sperm motility in a dose-dependent manner when used in concentrations from 16 to 64 μM (p < .01). The highest reduction was seen due to K4S4 activity, and the lowest reductions of sperm motility were observed due to K4S4(1-16)a and K4S4(1-15)a activity (p < .01). Hence, we can conclude that K4S4(1-16)a and K4S4(1-15)a at a concentration of approximately 15 µM are the most promising peptides as antibacterial agents in fresh bovine semen, because at this concentration, they showed the most potent antibacterial activity against evaluated strains without significant effects on haemolysis or a reduction in sperm motility.