Quality and in vitro fertilising ability of cryostored Pinzgau bull insemination doses

Applicability of cryopreserved insemination doses is dependent on the quality of the semen after thawing. The aim of the study was to check the options of new markers for the assessment of sperm quality to predict their fertilisation ability. In five bulls of the Pinzgau breed, the sperm fertilising ability was determined using the in vitro fertilisation. Bulls were divided according to the achieved blastocyst rate: bulls with good fertilising ability (NOB - 38.6%, KAZ - 28.9%, GAL - 29.3%) and bulls with low fertilising ability (LOH - 19.4%, NUS - 22.1%). In addition to the sperm motility and morphology, we monitored common physiological sperm characteristics: viability, apoptosis, acrosomal status, capacitation, mitochondrial activity and generation of reactive oxygen species using the flow cytometry procedure. Novel fertility-related biomarkers, such as ubiquitination, overexpression of MKRN1, SPTRX-3 and PAWP proteins or histone modification (H3K4me2), were also analysed by flow cytometry. From all monitored parameters, more proper characteristics of impaired in vitro fertilising ability proved to be high incidence of apoptotic markers (YO-PRO, Caspase 3/7) and higher counts of morphologically abnormal spermatozoa. Although the in vitro fertilisation (IVF) test can be an advantageous method for evaluating the sperm fertilising ability, there are still differences between the in vivo and in vitro fertilisation processes, which must be considered for example, when evaluating the sperm capacitation status.