| Seedstock EDGE Seedstock EDGE main | Seedstock EDGE archives Advertising rates/deadlines | Mail dates Subscribe today! | Seedstock EDGE staff |
August 2004 Issue
Stress gene revisited
by Darrell Anderson
I can assure you, it is with great reluctance that I once again feel compelled to discuss the stress gene. I have heard every possible argument on both sides of this controversial issue, and to be quite honest, I’m weary of the entire topic!
I have good friends and know well-respected breeders that possess differing opinions on this issue. The boards of directors for each of the four breeds have labored over this subject, and they have established policies that they believe are best for the long-term viability of our industry.
With the new policy that became effective last month, all breeders who register litters farrowed after July 1 must have their sires’ stress-negative status on file with our office. This has once again raised some questions about the stress gene and its impact on our industry.
With that in mind, I thought it would be helpful to share a new resolution that has been drafted by the National Pork Board Animal Science Committee. It is an updated revision of the NPPC resolution that was passed in 1996 by the delegate body.
I think the language of this proposed resolution and the rationale that supports it may be helpful to those that do not fully understand the negative impact of this gene in our industry.
2004 National Pork Board proposed resolution: That the pork industry take aggressive steps to eliminate all detrimental forms of the ryanodine receptor gene (also called the ”halothane” or “stress” gene) on chromosome 6 (mutation at position 1843 or any other mutations in this gene discovered in the future to have detrimental effects) from the U.S. swine herd, and further to aggressively eliminate all forms of other genes identified presently or in the future as having detrimental effects on pork muscle quality traits.
State/Producer rationale: The National Pork Board Vision Statement includes “Increasing per capita consumption of pork” as a primary goal of the U.S. pork industry.
Pork quality continues to be a major concern as the industry competes with other protein sources and the “stress” gene specifically, continues to negatively impact the pork industry in certain markets. Animal welfare also is a major concern of consumers and the potential for severe and traumatic stress reactions which produce extremely high mortality rates makes all detrimental forms of the ryanodine receptor gene unacceptable to the pork industry.
Committee rationale: A mutation at the 1843 position of the ryanodine receptor gene on chromosome 6 (also called the ”halothane” or “stress” gene) has been documented to cause susceptibility to a severe stress reaction in homozygous pigs, resulting in a high mortality rate, and in heterozygous pigs, results in minor increases in lean percentage but with significant decreases in meat quality.
Continued failure to eliminate this mutation and detrimental forms of any known or as yet undiscovered genes will contribute to long-term industry demand limitations and result in loss of consumer confidence in pork. Pork produced by pigs that have a detrimental form of the ryanodine receptor gene is tougher, has greater drip loss, and a greater incidence of PSE (pale, soft, exudative) muscle. Pork industry research indicates consumers discriminate against pork with poorer quality, particularly pork with the muscle quality implications produced by this mutation. Additionally, the production of pigs that are homozygous positive for this mutation produce a potential animal welfare issue due to the susceptibility of these pigs to severe and traumatic stress reactions which produce extremely high mortality rates.
Eliminating the mutant form of the ryanodine receptor gene (mutation at position 1843) and any other mutation of this gene, discovered in the future to have detrimental effects on meat quality, from the U.S. pig population will significantly improve the eating quality of pork. Because quality traits are undoubtedly affected by many other still-unidentified genes, the continued aggressive elimination of detrimental forms of those genes currently known, or as they are discovered in the future, should be aggressively pursued to ensure quality pork for the consumer and support promotion efforts.
As you can see, this resolution continues the efforts which began over nine years ago to eliminate the presence of the stress gene throughout our industry. It actually began nearly four decades ago when Dr. Lauren Christian discovered the negative aspects of this gene. We’ve tolerated the “bad” in an attempt to capture the “good” provided by this gene. It would be the opinion of your boards of directors that the “good” has been captured – it’s now time to rid ourselves of the gene altogether.
The pork industry has enjoyed incredible demand for our product so far this year, and all of you have reaped some of the benefits through higher prices. Now is the time to do everything possible to ensure that only the finest quality pork is being produced in this country. From a genetic standpoint, removal of the stress gene may be one of the easiest and most cost-efficient steps we can take to make that goal a reality.
