DNA Studies of Meat Quality

a brief review about some genes controlling meat quality or grade in Canada

This webpage was last updated on June 28, 2006 by Sheila Schmutz schmutz@sask.usask.ca

Leptin

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.

One example of a gene that we found to affect carcass quality is leptin. 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.

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
Angus 58% 30%
Hereford 55% 32%
Charolais 34% 10%
Simmental 32% 10%

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

Scientific Publications

  • Buchanan, F.C., C. J. Fitzsimmons, A. G. Van Kessel, T. D. Thue, D. C. Winkelman-Sim, S. M. Schmutz. 2002. A missense mutation in the bovine leptin gene is correlated with carcass fat content and leptin mRNA levels. Genetics, Selection, and Evolution 34: 1-12.
  • Buchanan, F.C, T. D. Thue, S. M. Schmutz August 12, 2002. Genes controlling appetite show interdependencies in allele frequency in beef cattle. International Society of Animal Genetics, Göttingen, Germany.
  • Thue, T. D., B.G. Goldade, A. Van Kessel, S. M. Schmutz, B. Laarveld, F.C. Buchanan. Jan. 17, 2001. Quantification of mRNA from adipose in beef cattle selected on genotype at the Obese gene. Plant and Animal Genome IX, San Diego, CA.
  • Fitzsimmons, C. J., S. M. Schmutz. Jan. 19, 1999. A SNP in the leptin gene leads to a change in the amino acid sequence of the mature protein in cattle. Plant and Animal Genome VII, San Diego, CA.
  • Fitzsimmons, C. J., S. M. Schmutz, R. D. Bergen, J. J. McKinnon. Jan. 19, 1998. Effects of the obese gene in beef cattle on carcass characteristics. Plant and Animal Genome VI, San Diego, CA.
  • Fitzsimmons, C. J., S. M. Schmutz, R. D. Bergen, J. J. McKinnon. 1998. A potential association between the BM 1500 microsatellite and fat deposition in beef cattle. Mammalian Genome 6:432-434.
  • Stone RT, Kappes SM, Beattie CW (1996) Two polymorphic microsatellites within an 18 kb genomic clone containing the bovine ob gene. Anim Genetics 27, 64

    • DNA Test for Leptin

    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. It is marketed worldwide by Merial as Igenity-L.

    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

    e-mail schmutz@sask.usask.ca

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