Hot on the heels of the pig genome comes news of another animal sequenced down on the farm. Writing in this week’s Science, researchers report the genome of Twilight, an adult female Equus caballus.

While this worthy feat of science has attracted much media interest, none of the coverage seems to mention that the horse genome was actually sequenced back in 2007 and widely reported at the time, although it was only published this week.

It is a useful genome to have though.

“Horses and humans suffer from similar illnesses, so identifying the genetic culprits in horses promises to deepen our knowledge of disease in both organisms,” says Kerstin Lindblad-Toh, of the Broad Institute of MIT and Harvard and Uppsala University in Sweden (press release). “The horse genome sequence is a key enabling resource toward this goal.”

The equine sequence is roughly 2.7 billion letters long and is not dissimilar to our own. “Indeed, 17 horse chromosomes (53%) comprise material from a single human chromosome (in the dog, it is 29%),” the authors write.

The horse genome joins not only the pig, but also the chicken and the cow, with the sheep on the way. All together now: “Old Macdonald had a genome…”

Image: Twilight / courtesy of Doug Antczak, Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University