DNA Studies Genes Affecting Meat Quality in Beef Cattle
a brief review about one example gene controlling meat quality or grade in Canada
This webpage was last updated on November 16, 2013 by Sheila Schmutz firstname.lastname@example.org
Effects based on Leptin Genotypes
|Canada grades beef primarily on the amount of marbling present within the steak. Ranchers try to breed for cattle of AAA or premium grade because they receive a payment bonus for delivering beef of such quality. Feeding is also important, of course, so that cattle are finished properly before slaughter. Marbling affects the flavor of the meat. It also adds juiciness, even when steaks are cooked well.|
Leptin is a hormone in the fat metabolism pathway that has been shown to affect the amount of fat deposition in beef. A DNA variant alters a critical amino acid which affects the folding of this hormone. The leaner cattle have a "C" and the more marbled cattle a "T" in the critical position. Therefore cattle are CC, CT or TT. For more details about why this mutation has "causative" effects, see another webpage.
Leptin research began some years ago in our lab. Several cattle trials involving both purebred and crossbred cattle in several feeding situations have been conducted. Although the results vary in terms of the proportion that grade AAA or higher, the trend has always been the same: TT cattle have a much higher chance of AAA, or in the U.S. system "choice".
Because this T variant is inherited, a beef producer can try to purchase bulls that are TT and then know that every calf sired by such a bull will receive a T from him. The other allele of each calf obviously comes from its dam and so depending on the genotypes of the dams in the herd, calves could be TC or TT. Nevertheless the TT bull would ensure that all have a better chance of achieving a higher grade.
All of the cattle breeds that we have studied have both CC and TT animals. The proportion of these alleles does vary among breeds. The table below shows proportion of T in breeds where we have tested a sufficient number of purebreds to estimate this.
|Breed||Frequency of T variant||Proportion TT|
Articles in the Popular Press
....Who's the tenderest of them all? Western Producer, June 4, 1998. D'Arce McMillan.
Scientists Search Genes for Beef Tenderness,, Western Producer, March 16, 2000, p. 97. D'Arce McMillan.
DNA Research on Meat Quality. Cattlemen magazine, June/July 2001 issue. p. 18-19. Sheila Schmutz.
New DNA test could someday select sires for fat or lean. Cattlemen magazine, May 1999 issue. p. 20-21. Carolyn Fitzsimmons
A simple DNA test is available from Quantum Genetics 8 - 410 Downey Road, Innovation Place, Saskatoon, SK Canada S7N 4N1 306-956-2071 Fax: 306-956-2066
DNA can be collected from hair roots, blood, semen, milk, etc. Although it was previously marketed by Merial as Igenity-L, this particular test is available now only from Quantum Genetics.
Other Genes Studied More Recently
There is a family of melanocortin receptors genes. Although MC1R is traditionally associated only with pigmentation in animals, data collected and analyzed by Kim McLean during her PhD studies, suggests that this gene also affects fat depostion, perhaps indirectly.
She also studied MC4R, a gene in this family that has been associated with carcass traits in other species previously. A SNP is this gene is associated with carcass fat in beef cattle.
Sarah Helgeson studied PMCH and identified a mutation in the promoter region that affected fat deposition. She also has preliminary data that tenderness was also affected.
Julie Goodall discovered a mutation in IGF2 which affects rib-eye area in beef cattle. Similarly others have discovered that a mutation in this gene affects ham size in pigs.
for further information contact:
Department of Animal and Poultry Science
University of Saskatchewan
Saskatoon, Canada S7N 5A8
phone: (306)966-4153 fax: (306)966-4151