Genetic advancements to deliver great improvements in sheep flock

COST reductions and pooled international research into sheep genomics could soon lead to a dramatic improvement in the Irish flock.

Teagasc researcher Dr Orla Keane believes that the singling out of individual gene traits and genetic selection in sheep will lead to a significant improvement in the Irish flock.

New DNA chip technology and other pooled global technical advances should see the International Sheep Genomics Consortium (ISGC) release some very positive results before the end of 2011.

Dr Keane said: “Results from the sheep genome project are expected to be released later this year. This will detail a genetic reference sequence in the Texel breed, which will provide a blueprint of the sheep genome, a map of the genes that are present in sheep and their sequence.

“This will allow the identification of genetic components. It will allow the mapping of single gene traits. Some have been found, and there are more in the research pipeline. We will be able to single out the genes responsible for complex traits like disease resistance,” she added.

Similar research is already delivering accelerated genetic gain to the Irish cattle herd. Until now, the lower value of sheep relative to cattle has seen lesser funding being allocated to research on the sheep genome.

However, in the last ten years the cost of genetic sequencing has decreased by more than three orders of magnitude. For example, the original human genome sequencing project cost over US$2bn. Currently it would cost substantially less than US$1m to sequence a human genome.

The ISGC has used a newly developed chip to genotype approximately 3,000 sheep of 74 breeds from around the world in the Sheep HapMap and breed diversity project.

The sheep genotyped included approximately 50 each of the Galway and Suffolk breeds sourced from Teagasc and University College Dublin flocks.

Dr Keane adds: “The technology also makes mapping the gene responsible for a single gene recessive trait relatively straightforward.

“Since the chip was released, the technology has been successfully used to map or identify the gene responsible for microphthalmia (a recessive disorder causing blindness) and chondroplasia (a disease resulting in dwarfism and deformity of the limbs) in the Texel breed, yellow fat in the Perendale breed, and the gene responsible for polledness (ie absence of horns).

“As part of the EU Seventh Framework Programme 3SR project (Sustainable Solutions for Small Ruminants), the technology is currently being utilised by Teagasc researchers, in collaboration with the ISGC, to map the gene responsible for increased ovulation rate in the highly prolific Cambridge flock at the Teagasc Animal & Grassland Research and Innovation Centre, Athenry.”

Such examples of gene identification can have an immediate impact on the sheep breeding industry by allowing sheep breeders to screen animals for the genes and select replacement stock, cull or avoid at-risk matings based on the results.

The technology is also currently being utilised by Teagasc and collaborators to identify genes underpinning polygenic traits, such as production traits and parasite resistance.

Furthermore, the technology is a fundamental tool required for genomic selection, where animals are selected on genomic rather than phenotypic characteristics.

While genetic research into sheep has really just begun to take off, Teagasc experts, including Seamus Hanrahan, have done a lot of groundbreaking work in the area over the years.

Progress of this latest research will be closely followed by Sheep Ireland and others.