Mapping the swine genome is a work in progress. Much progress has been made, and more will come. For now, four genetic markers that are associated with growth, leanness and meat quality are available to all U.S. pork producers.

This action comes through a licensing agreement inked between Iowa State University Research Foundation and GeneSeek of Lincoln, Neb. All four of the DNA markers have already been tested and commercially validated by PIC.

“This is the first opportunity to select for traits using markers, apart from some of the original deleterious markers like Halothane and RN (Napole) genes,” notes Max Rothschild, IowaState swine geneticist and national swine genome director. “This is the first wave of genes affecting growth, backfat and meat quality.” It’s also another step in the progression of discovering genes and getting them out to the marketplace.

So, let’s take a look at what the markers have to offer.

MC4R — This marker controls hog growth and leanness. “Producers and breeders can choose from a fast-growth form of the gene or a lean/efficient-growth form of the gene,” Rothschild says.

 As a result, hogs carrying two identical forms of the allele for growth reach market weight three days faster, on average, compared to hogs carrying the two identical forms of the lean gene.

Pigs homozygous for the lean allele carry 8 percent less backfat and consume significantly less feed than their homozygous growth-allele counterparts.

This technology will let breeders select the characteristic — growth or leanness — that they consider to be best suited for their program, Rothschild says.

The results have been validated and are effective in all breeds except for the Hampshire breed. “That’s because these are already fixed in the Hampshire breed — there’s no genetic variability on this,” he adds.

PRKAG3 — Through this marker, producers and breeders can select animals having a high pH and improved meat color form of the gene. As pH is aligned with high pork quality, this genotype offers increasing benefits. Hogs with this homozygous genotype have a pH level that’s nearly 0.1 higher in the loin and ham muscles compared with hogs that are homozygous for the non-beneficial allele. These effects are seen in all major breeds, says Mark Boggess, National Pork Board’s director of animal science.

CAST — This gene affects tenderness and meat quality. Its usage will allow the industry to test and select for animals that are likely to produce tender meat with improved meat quality.

HMGA1 — This is a marker that’s highly associated with backfat and lean growth. The use of this marker will allow producers to test for and select animals that are more likely to be lean and produce lean offspring. The end result will be the enhanced ability to produce a consistently lean end product.

The best part is that the effect of these genes is additive, so they can be maximized by using the genes in various combinations. “Using all four would be beneficial for overall line development to reduce days to market, improve leanness and meat quality,” Boggess notes.

Or you could select and refine the combinations for more specific gains. For example, combining MC4R (growth allele) and HMGA1 could be used to improve growth and backfat levels. The MC4R (lean allele) and HMGA1 could be used together for significant lean gains in breeding stock and their progeny. Finally, PRKAG3 and CAST could be combined with the objective of improving meat quality.

Seedstock producers and genetic companies will be the ones to use the markers, but the results will trickle down to benefit producers industry wide. “Now, the opportunities exist for breeders and producers to more directly develop the best multi-gene combination for their lines,” Boggess says.

But the job isn’t done. There are more prospects to dig through and gene markers to uncover. “There are more DNA markers and DNA marker technologies not too far down the road,” he adds.

Rothschild points out that IowaState is working on markers related to litter size and sow longevity. “Probably by early spring we will see two or more markers that will affect litter size and sow longevity,” he notes.

As NPB has been involved in funding the international effort to sequence the swine genome, it continues to sponsor research to develop additional genomic technologies. “Included in NPB’s research priorities is a study reviewing pigs’ abilities to resist or better tolerate disease agents, specifically porcine reproductive and respiratory syndrome virus,” Boggess says.

Clearly, more dynamic applications will continue to unfold.