September 2011

Studies show muscle gene can enhance sow performance, too

Research scientists at the University of Leuven, Belgium, the Canadian Centre for Swine Research and RattlerowSeghers are using a unique selection scheme that can improve sow performance without jeopardizing leanness and uniformity of the slaughter generation.
The selection method focuses on the IGF2 gene, a unique marker that has been identified as a key gene in improving muscle mass, leanness and uniformity in terminal sires and their progeny.
However, scientists have now shown that IGF2 has equal significance for dam lines. Results from two independent studies performed in Belgium and Canada* show that the recessive paternal gene (IGF2-) does influence reproductive performance and sow longevity. Sow lines that expressed the recessive gene were found to wean 0.5 pigs per litter more and have significantly higher weaning - averaging 4kg more per litter.

Manipulation
Many breeding companies use the IGF2 marker within terminal sires selection programmes, selecting boars that are homozygous for this gene (IGF2+) because of the benefits they can pass on to their progeny.

But by exploiting the way the gene is inherited, they are now able to manipulate breeding programmes to improve sow prolificacy and longevity, too.
Pigs that carry the recessive gene (IGF2-) have higher back fat levels and less muscle - traits that benefit dam lines.

“IGF2 is important for both male and female selection programmes because of its key influence on leanness and muscle development. In dam lines it is useful because it allows breeders to distinguish which females have a higher potential for lean growth and those that don’t, ” explains Professor Nadine Buys, Director of Gentec. Prof Buys discovered the marker almost five years ago and it is now a valuable tool within genetic development programmes.

“In simple terms, with dam lines we select for the opposite characteristics that we want to see in terminal sires and the traits associated with the recessive gene are very favourable in gilt breeding programmes,“ adds Prof Buys.

Dominant rewards, with recessive benefits too
Only boars carrying the dominant IGF2+ gene, will display increased muscle mass and leanness. And, because the gene is paternally imprinted - which means it is only active in the offspring when it is passed on from the father - these favourable conformation traits cannot be inherited from the dam.

Therefore, if dam line GP boars are selected only to have the recessive IGF2 gene, then they will successfully pass on its inherent characteristics to their daughters. Although these daughters may be ’fatter’ they will not be able to pass this undesirable genetic effect to their progeny. Therefore carcase quality in the slaughter generation will not be compromised.

In simple terms using this gene within selection programmes means geneticists can breed fatter dam lines capable of better reproductive performance that will not pass on negative carcase traits. On the sire side, commercial producers that use proven IGF2+ homozygous terminal boars, such as Rattlerow’s BetterGEN muscle+ sire lines, can exploit their advantages of better carcase quality as ALL of their progeny are guaranteed to inherit the traits for increased muscle mass, leanness and uniformity.

KEY FACTS FOR IGF2
Dominant gene IGF2+ is linked to higher muscle mass.
Homozygous terminal sires with the dominant gene will pass on its full effect to his slaughter progeny. The genotype of the mother does not influence the muscle mass.
The recessive gene IGF2- is linked to higher body reserves and increased prolificacy
Progeny from sows with the recessive gene tend to have more back fat, and as a result are better equipped for a prolific and productive life.

*Reference: Published in Animal Genetics November 2010

Return to main news page