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Gene Markers

Hair today, gene tomorrow

A cattle-testing service that requires only a few strands of the animal’s hair could revolutionise the way in which livestock producers select animals for breeding.

Using the same technology that allows the police to ‘DNA fingerprint’ crime suspects, cattle producers now have access to the genetic make-up of their prime animals, allowing more objective breeding decisions to be made in order to deliver specific traits.

“Now that we understand the relevance of specific gene markers in the cow, it’s possible to identify whether an animal carries any one of a number of heritable characteristics,” says Andy Forbes, head of technical services at Merial Animal Health.

“Wouldn’t it be useful to be able to identify the genes responsible for improved milk yield, higher fat, better protein levels, meat tenderness…and many more?

“Armed with such information, we could develop breeding and management programmes which would allow animals to develop their full genetic potential and improve the profitability of the herd and the business,” he enthuses.

Although the technology doesn’t yet promise to deliver the ‘perfect’ cow, Merial’s IGENITY testing service marks an exciting new chapter in cattle breeding techniques. Minor changes in genes, known as ‘single nucleotide polymorphisms’ – ‘snips’ – can be analysed and used to define an animal’s true potential. The test can be carried out using just a few strands of hair plucked from the animal’s tail-switch.

“The very first test we launched as part of the IGENITY system was IGENITY-L,” explains Mr Forbes. “It identified which one of two kinds of leptin – an appetite-regulating protein – that an animal produces.

“Determine which form of leptin a dairy or beef cow is producing, and it is possible to work out her potential for a range of functions, such as appetite, energy use and fat deposition. In turn, of course, such factors affect headline figures such as milk yield. We’ve found that cows producing only the ‘t’ form of leptin produce up to 1.5kgs more milk per day than cows with the ‘c’ form only.”

IGENITY-L’s favourable launch reception in 2004 has encouraged Merial to bring forward its plans for the IGENITY system, resulting in the launch of a further four tests over the past six months. Of particular significance to beef breeds are IGENITY OptiYIELD and TenderGENE.

“OptiYIELD allows identification of a cow’s genetic potential for milk and fat yield,” explains Mr Forbes. “Suckler herds using beef breeds which are traditionally low-yielders could simply select cows which are genetically pre-disposed to higher yields.

“In technical speak, OptiYIELD identifies a natural variation in the DGAT1 gene which plays an important part in fat synthesis and milk production.

Widespread research has confirmed the role of the DGAT gene, says Mr Forbes. For example, 90% of North American Holsteins were found to have the gene corresponding to high yields and protein levels, while 77% of New Zealand Jerseys were found to have the variation that corresponds to greater fat kg and percentage.

As for the TenderGENE test, it’s already being used in the US to great effect. There, beef producers are earning a premium of up to £80 a carcass for beasts guaranteed to be tender.

“Animals are selected by identifying the presence of calpain,” says Mr Forbes. “A naturally-occurring protein, it enhances meat tenderness by weakening muscle fibres during the post-mortem period.

“It’s no secret that here in the UK, poor tenderness has been identified as one of the industry’s major challenges – yet here’s a product which enables beef to be labelled as tender, and which, when marketed properly, should attract premium-paying consumers.”

Mr Forbes says that the US Simmental Association has just incorporated TenderGENE into its EBV for tenderness. “The test’s been available there for three years and it’s the pedigree breeders, supplying stock to commercial producers, who have really bought into it.

“What’s great about IGENITY is that it’s a positive addition to the role of the ‘stockman’s eye’ that so many breeders value so highly.

“Breeding’s never going to be a perfect science, but IGENITY will help make selection and breeding decisions much more precise and allow producers to justify their decisions more readily.”