How high the moo

DNA extracted from a 6500-year-old ox bone has helped an international team of scientists identify the genes that determine the height of cows.

In future, the finding, published in the journal Nature Genetics, will help cattle breeders better control the size of their animals. It also establishes a process by which genetics can be used to influence other factors, such as muscle density, milk volume, and even gas emissions.

The ancient wild ox bone belonged to a now-extinct species known as an aurochs (Bos taurus primigenius), which has been shown to be a foundation ancestor of modern cows.

Genetic material extracted from the bone formed a critical reference point for scientists led by Ben Hayes, from the University of Queensland in Australia.

Hayes heads up a study mission, involving 30 institutions around the world, called the 1000 Bull Genomes Project – which aims to collect a large dataset of male cattle genetic information to allow better insight into the factors that control the development of the animals.

Identifying specific genes that influence individual traits is challenging, however, because of variations across multiple gene clusters, diet, and environmental conditions all contribute to the size and shape of cattle.

To start to narrow down genetic targets and eliminate non-genetic influences, Hayes and his colleagues pooled genome datasets and physical information for 58,000 cattle from 27 populations around the world. The result was a pool of 25.4 million whole-genome sequence variants.

These were compared to two bovine reference points – the aurochs DNA, and genetic material extracted from miniature versions of Angus, Belted Galloway and Hereford cows.

“Aurochs are an extinct species of large wild ox – which were domesticated by ancient humans about 10,000 years ago and bred to be shorter – and are the ancestor to all cattle breeds,” explains Hayes.

“From analysing the DNA of this animal, we could predict its height, and then verify our prediction with the fossil records of aurochs skeletons. On the other hand, the miniature cattle were predicted to be quite small based on their DNA and the genes we pinpointed in the study, validating our discoveries.”

The team then compared their results to human and dog genomes and found considerable overlap in height-influencing genes. This was a new discovery.

“The same genes influencing height in cattle also influence the trait in other mammalian species,” says Hayes. “This is something that has never been demonstrated before.”

As an unexpected additional find, the research strongly indicated that the determination of height in dogs is governed by a larger set of genes than earlier studies had suggested.

Hayes and his team identified 163 regions in cattle genomes that are associated with height, opening the way for them to be manipulated to better control the trait by breeders. The approach, too, promises to be useful in influencing other cow characteristics.

“By applying the same collaborative big data approach, it may now be possible to identify genes associated with high-value complex traits that are really important to the industry, such as beef and milk production, feed efficiency and reduced methane emissions,” Hayes says.