Copy number variation (CNV) is defined as large-scale deletions of or gains in DNA fragments, according to Wageningen University & Research (WUR) in the Netherlands. CNVs can have a large effect when they are present in genes or in regions of regulatory elements.

In livestock, WUR said CNVs have been studied for their possible association with economically important traits such as milk production and fertility.

In recent research, WUR reported that the signal intensity data of the 777K BovineHD genotyping array was used to identify CNVs and to study their distribution in the genome of various European cattle breeds. The study was published in Frontiers in Genetics.

The study highlighted possible associations between effective population size and CNV distribution in cattle breeds, WUR said. Additionally, the study also concluded that CNV might be playing an important role in exhibition of traits related to immunity, olfaction and coat color.

According to WUR, the study reported differences in abundance of CNV counts between European cattle breeds. Cattle from the British Isles, Balkans and Italian regions, on average, displayed a higher abundance of CNV counts than Dutch or Alpine cattle, WUR said.

Many CNVs were partially or completely shared among cattle from the different regions, indicating low population differentiation. These results were attributed to differential effective population size and selection pressure that exists between European cattle breeds. It was noted, however, that this hypothesis needs further validation using a large sample size, WUR noted.

The enrichment of CNVs in the immunity-related genes may partially explain the immune response variability among different breeds to certain diseases, WUR reported. Additionally, genomic rearrangement involving duplication of a genetic segment, which was first reported in Belgian blue cattle and associated with coat color-sidedness, was identified in English longhorn cattle.