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A large international project identified a set of common genes in mammals that regulate their body size. Some of the genes regulating size studied in 17 populations of cattle were the same as ones that have previously been identified in humans and dogs.

The new results that have been published in the esteemed Nature Genetics journal are based on data of unprecedented size: it included 17 cattle populations. Of these populations, the entire genome of over 58,000 cattle was predicted.

“First, the impact of the differences of entire genomes on animal size was analysed one population at a time. After that, the results were combined by conducting a meta-analysis”, says Johanna Vilkki, research professor at Luke.

The Natural Resources Institute Finland (Luke) participated in the project with a research on the stature of animals that covered the whole genome of the Finnish Ayrshire cattle.

The entire genome of over 58,000 cattle was predicted in an international study. Photo: Janne Lehtinen.

The research identified 163 genomic regions where variance explained at most 14% of body size variance in one population. Most of the regions regulating body size were not found in actual genes but in control regions.

The research confirms that the size of mammals is a trait regulated by multiple factors and a large set of genes. Previously, it has been suggested that the size of dogs, for example, varies largely due to variants in a small number of genes. These conclusions lead researchers to compare different breeds.

“The study that has just been published analysed dog populations and showed that also the stature of dogs is regulated by a larger set of genes than previously thought”, Vilkki says.

Many of the genes regulating the size of modern cattle originate from the aurochs

The project also evaluated the origin of the alleles that regulate the body size of animals and the time when these alleles were created. This was done by comparing the genome of modern cattle with the genome of the aurochs. Modern cattle are a descendant of the now-extinct aurochs. According to the bone samples found, the aurochs was larger than modern cattle.

“The research showed that many alleles that increase the size of cattle originate from the aurochs, and at least from the time before different cattle breeds were born”, Vilkki says.

After cattle was domesticated, people have chosen smaller animals on purpose so that, for example in the Medieval Period, the cattle’s height at the withers was less than a metre. Later, people started to select larger animals again so that the wither height of some breeds, such as Holstein cattle, has increased by approximately 2mm per year over the past few decades.

“The variance in selecting cattle size may have helped to preserve the ancient size variance in modern cattle.”

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