Role of seminal MDA, ROS, and antioxidants in cryopreservation and their kinetics under the influence of ejaculatory abstinence in bovine semen

Despite many cryopreservation techniques in bovine semen, various stressors' detrimental effects remain a significant issue. The present study targeted to assess the role of semen quality parameters, sperm function tests, lipid peroxidation, reactive oxygen species (ROS), and different antioxidants in the cryopreservation of bovine semen. Further, the kinetics of lipid peroxidation, ROS, and antioxidants on repeated semen collection under short ejaculatory abstinence were studied. We designed a comparative study where bulls were grouped into good and low freezable semen groups (Freeze-groups) based on their post-thaw motility. All the bulls included had similar initial motility and qualified minimum standards for initial semen parameters viz. semen volume and sperm concentration. The present study detected a higher lipid peroxidation and ROS viz. superoxide anions (•O2-) and a lower total antioxidant capacity (TAC) in the low freeze-group compared to the good freeze-group. The ROS and antioxidants showed unique kinetics on repeated semen collection at short intervals, and no significant change was detected in semen volume, sperm motility, and sperm concentration. This study detected higher head abnormalities and poor acrosome integrity in the low freeze-groups. The present study results indicated that the sperm head might be the most vulnerable part of the sperm to cryopreservation stress. The present study finds significantly higher lipid peroxidation and ROS levels and reduced antioxidant capacity as the primary reasons for low cryopreservability. Further, repeated semen collection with a shorter or lack of abstinence does not impose any significant change in the semen volume and sperm concentration; moreover, it could be beneficial for higher antioxidant levels and lower lipid peroxidation levels. As seminal plasma has both inhibitory and stimulatory roles in sperm function and cryopreservation, identifying the critical role players of seminal plasma and identifying sperm related changes in cryopreservation could predict the cryopreservability potential of semen.

Semen as a source of Mycoplasma bovis mastitis in dairy herds

Mycoplasma bovis infections are responsible for substantial economic losses in the cattle industry, have significant welfare effects and increase antibiotic use. The pathogen is often introduced into naive herds through healthy carrier animals. In countries with a low prevalence of M. bovis, transmission from less common sources can be better explored as the pathogen has limited circulation compared to high prevalence populations. In this study, we describe how M. bovis was introduced into two closed and adequately biosecure dairy herds through the use of contaminated semen during artificial insemination (AI), leading to mastitis outbreak in both herds. Epidemiological analysis did not reveal an infection source other than semen. In both farms the primary clinical cases were M. bovis mastitis in cows inseminated with the semen of the same bull four weeks before the onset of the disease. One semen straw derived from the semen tank on the farm and other semen lots of this bull were positive for M. bovis. In contrast, semen samples were negative from other bulls that had been used for insemination in previous or later oestrus to those cows with M. bovis mastitis. Furthermore, cgMLST of M. bovis isolates supported the epidemiological results. To our knowledge this is the first study describing the introduction of M. bovis infection into a naive dairy herd via processed semen. The antibiotics used in semen extenders should be re-evaluated in order to provide farms with M. bovis-free semen or tested M. bovis-free semen should be available.

Cryopreservation of bull semen: Evolution from egg yolk based to soybean based extenders

Since the inception of bovine semen cryopreservation, egg yolk and milk based extenders have been used to protect sperm from the detrimental effects of cooling and freezing. In recent years, demand for alternatives to conventional commercial extenders has arisen as the risk of introducing exotic diseases through transporting egg yolk based products has been recognized. Egg yolk can also interfere with sperm evaluation and the presence of particulate material in the extender may reduce fertility. Soybeans contain lecithin, a phospholipid fraction that can substitute for high molecular weight lipoprotein and phospholipids from egg yolk and prevent or ameliorate damage to the sperm plasma membrane that occurs during extension, cooling, and cryopreservation. Soy lecithin based extenders have been evaluated for processing and freezing bovine semen, although extender from soybean milk has not been studied as extensively. Commercially available soy lecithin based extenders are used increasingly but remain under scrutiny and are not universally accepted. With these observations in mind, this review is intended to examine effects of conventional cryopreservation procedures, methods of assessment, and potential for developing soybean extract as an acceptable alternative to traditional egg yolk and milk based extenders for bull sperm cryopreservation.

in Spiked Bovine Semen Using Loop-Mediated Isothermal Amplification (LAMP) Assay

Several pathogens including Brucella spp. are shed in semen of infected bulls and can be transmitted to cows through contaminated semen during artificial insemination. The present study reports omp2a and bcsp31 gene based loop-mediated isothermal amplification (LAMP) assays for detection of Brucella genomic DNA in semen from infected bulls. The positive results could be interpreted visually by change in colour of reaction mixture containing hydroxyl naphthol blue (HNB) dye from violet to sky blue. LAMP assays based on omp2a and bcsp31 could detect as little as 10 and 100 fg of B. abortus S19 genomic DNA, respectively. Sensitivity of omp2a and bcsp31 LAMP assays for direct detection of organisms in bovine semen was 2.28 × 10(1) CFU and 2.28 × 10(2) CFU of B. abortus S19 in spiked bovine semen, respectively. The omp2a LAMP assay was found equally sensitive to TaqMan probe based real-time PCR and 100 times more sensitive than conventional PCR in identifying Brucella in spiked semen. The diagnostic applicability of the omp2a LAMP assay was evaluated with seventy-nine bovine semen samples and results were re-evaluated through TaqMan probe based real-time PCR and conventional PCR. Taken together, the omp2a LAMP assay is easy to perform, rapid and sensitive in diagnosis of Brucella spp. in bovine semen.

Development of a SYBR Green I based duplex real-time PCR for detection of bovine herpesvirus-1 in semen

Bovine herpesvirus-1 (BoHV-1) is a viral pathogen found in infected bull semen, which is transmitted to inseminated cows by artificial insemination. BoHV-1 infection can cause reproductive disorders leading to significant economic loss to cattle industry. To detect BoHV-1 in semen, in this study, a SYBR Green I based duplex real-time PCR was developed. The assay included primers from BoHV-1 glycoprotein C (gC) and bovine growth hormone (bGH) genes for simultaneous detection in single tube. The result was interpreted by analysing melting temperature (Tm) peaks obtained after melt curve analysis of the amplified products at the end of reaction. The Tm peaks for BoHV-1-gC indicated presence of BoHV-1 while the bGH peak indicated reaction without inhibition. The sensitivity of the assay was to detect ten BoHV-1 genome copies per reaction. The analytical sensitivity was to detect 0.21 TCID50 infectious BoHV-1 in spiked semen. The assay was validated with 80 semen samples collected from breeding bulls. The diagnostic sensitivity and specificity of the assay was 100% with OIE recommended TaqMan probe based real-time PCR.