Unrivalled precision correlates % prog motility and conception rates
High-fertility bulls have spermatozoa with good flagella structure and function
At the EU AI Vet in the UK in October 2022, Dr Maria Belen Rabaglino from the University College Dublin presented a fascinating talk titled ‘Identification of Biomarkers of Bovine Sperm Function and Embryo Development using an Omics Approach’. She assessed the genes of both high and low-fertility bulls from the Irish population and discovered that genes associated with good flagella structure and function were prevalent in the high-fertility bulls. During question time, a member of the audience enquired as to whether any difference in motility had been observed using laboratory-based Computer Aided Semen Analysers, and, unfortunately, no correlation had been observed.
Ciara O’Meara from the National Cattle Breeding Centre was keen to try the Dynescan Semen Analyser to explore whether it could reveal new insights. Measurements were taken using 3 batches of conventional bull semen from each of six bulls spanning the range of low to high fertility in the Irish population. Conception rates were collected at a national level over approximately 20 independent batches for each bull corresponding to thousands of inseminations across a range of farms across Ireland under a wide range of conditions.
Measurements with the Dynescan Semen Analyser confirm there is a correlation between the % progressive motility measured at early times when the spermatozoa were swimming in an oxygen-rich (aerobic) environment and the in-field conception rates, as shown in Figure 1, with a gentle gradient of 0.64 (presuming linear dependence, R2=0.99) between the % progressive motility and resulting conception rate and a total range of less than 20% progressive motility between the low and high fertility bulls. Error bars show the standard deviation between independent batches for the same bull. In the literature, repeated CASA measurements have been shown to have a standard deviation error of around 10%, and therefore, it is not surprising that CASA measurements could not reveal this correlation. The Dynescan Semen Analyser provides measurements over a volume of sample that is 10x that of a CASA instrument for 60x longer than a CASA (each video 30s long). Furthermore, no dilution is required, thus removing errors due to incompatibility between the extender and the diluent. This offers much greater precision when performing measurements of the % progressive motility so that it is mainly batch-to-batch variation which dominates the data. In the future, we will look to correlate individual batch data with in the field fertility data at a grand scale.