Following these observations, Carole Charlier’s team is currently developing an entirely new research project aimed at detecting other mutations which behave in the same way, that is to say mutations which are responsible for early embryonic death. “This type of mutation affects the fertility of animals without the farmer being any the wiser as he does not see any calves dying at birth. It is more likely that each livestock population shows other deleterious mutations of this kind which have an insidious effect and a largely underestimated overall impact on fertility” she explains.

Tracking diseases that cause early embryonic death

Rolling up their sleeves to take on this new research project which is the main subject of Wanbo Li’s doctoral thesis, scientists have selected bulls that are mainly used for artificial insemination worldwide. “It is also thanks to the GIGA-Genotranscriptomics platform that we are in the process of sequencing their exome, that is to say the coding part of their genome, in order to identify mutations that are potentially deleterious. These mutations can be deleterious for different reasons, notably because they introduce a stop codon, lead to a delay in the reading phase or because they affect the splicing of genes for example”, Carole Charlier continues.

Because the bulls used for artificial insemination are handpicked and perfectly healthy, potential deleterious mutations that the team from Liege is searching for hide in their genome in the heterozygous state that is to say in single-copy only.  “We are going to try to identify them and make a list of these mutations. The idea is to then develop genetic tests making it possible to examine each population in detail, statistically, we will then be able to estimate the frequency of these mutations in the different populations”, adds the researcher. If, in the case of the brachyspina syndrome, scientists discover that the frequency of carrier animals of a mutation is relatively high but no living animal presents two copies of this, they will know that this mutation causes early embryonic death. The impact of the mutations that are identified as having an effect on bovine fertility could then be traditionally estimated by comparing the fertility data of carrier and non-carrier bulls.