The flaw, or "variation" as LIC is calling it, has been dubbed Fertility1 and is carried by about 3% of Jerseys and about 1.5% of crossbreds. It's extremely rare in Friesians, only occurring where there's an element of Jersey somewhere in the ancestry.
LIC general manager of research and development, Richard Spelman, says the variation affects fertility and calf survival. Embryos carrying double copies of the recessive gene are thought to die in utero or are stillborn.
"No live animals have been seen [exhibiting] the variation."
Analysis of stored genetics shows the trait's been in the New Zealand dairy cow population for more than 40 years with carrier sires identified from the 1970s.
The trait is recessive, so is only exhibited when both sire and dam are carriers and even then only 25% of progeny.
Spelman says LIC will genotype all of its active bulls and may still use carrier bulls where their genetic merit warrants use.
"DataMate, used by LIC AB Technicians, will issue alerts to reduce the frequency of matings between two carriers of the variation, and a genotype test will be available to farmers, wanting to test their cows, through GeneMark."
LIC says that in a Jersey herd of 400 cows there would likely be 12 carrier animals but because carrier cow has to mate with carrier bull, and even then only one if four calves are affected, it's likely only one animal per herd of 400 Jerseys will have been affected by the trait (ie missed a pregnancy or had a still born calf) in the past five years.
LIC is DNA screening its bulls for the trait and says the test will be made available to other genetics companies so they can screen their bulls.
Over time, the gene variation will be managed out of the national herd, LIC says. It doesn't know the gene's frequency in overseas genetics, but about 300 New Zealand sires from the last 30 years have been identified as possible carriers. A list of probable carriers in LIC's current stable is at the end of this article.
LIC says the DNA sequencing technology allows it to map and compare the DNA profiles of animals, identifying differences.
"Comparing the DNA sequence of a large number of sires has enabled LIC to identify a specific segment of DNA – one piece out of 3.2 billion – which is linked to the Fertility1 variation," says Spelman.
Fertility1 is the latest in a long line of recessive undesirable genes discovered in dairy animals around the world including CVM, BLAD, DUMPS, Brachyspina, Factor XI, Mulefoot and, more recently, Small Calf Syndrome.
LIC says the discovery of each genetic variation has led to the introduction of managed programmes which have significantly reduced them in dairy populations both internationally and in New Zealand. Its advice to farmers is to continue to record parentage of animals accurately so tools such as DATAMATE can be used to minimise the frequency of carrier to carrier matings.
The Fertility1 discovery was enabled by the sequencing dataset developed by LIC scientists and co-funded by Government through the Primary Growth Partnership.
LIC lists the following high use bulls as having been identified as carriers in "early but not definitive results": Gloaming SS Forever GR; Forbrae Taurus GR; Kirks RI Charisma ET GR; Bourkes Nimrod; Glanton Red Dante; Marivale Senator; Baylea Brass Albert; Deercrest Glenduan; SR Jellymans Atlanta; Lostahill Forevers Blake; William Ace of Hearts; Errlyn SS Pride GR; Kokofu Peppermint; SRB Newstead Governor; Priests Solaris ET; Williams TGM Henry; Harveys Zachary; Rockhaven Forever Sam; Marsden Red Athol; Howies Conqueror; Priests Brigadier; St Peters Obsidian; Puketawa Mins Supernova; Howies Easyrider; McDonalds Tweed ET; Ewings Ebony; Keystone HE Orpheus; Crescent AMC Marvel; Lynbrook Opium Trail; Marsden PMS Jade; Lynbrook Super Trickster; Lynbrook HTA Trifecta ET; Kerstens KRC Ronaldo; Tawa Grove KRC Tana; Colfols Crikey; Bells Solaris Perry; Howies Arkan Ramada ET; Scotts Bravo ET.
