Cattle producers are one step closer to taking the guesswork out of breeding and management decisions. A series of DNA tests being rolled out by Merial promises to identify the gene in cattle responsible for producing leptin — a protein that regulates appetite, energy use, fat deposition and marbling.

The company's new IGENITY L testing service will help cattle producers breed, raise, manage and market cattle of known ability to marble, says Stewart Bauck, DVM, head of Merial's livestock productivity business.

“IGENITY L testing identifies which type of leptin-coding genes an animal has inherited from its sire and dam,” says Bauck. “How the traits are paired has a major impact on beef production.”

Leptin is produced by DNA in fat cells. It is secreted into the bloodstream, where it is exposed to receptor sites in the brain.

Scientists have discovered two forms of leptin protein produced by cattle. One diminishes appetite, reducing production. The other keeps the animal in a “hunger mode.” This naturally occurring variation is a function of information encoded in DNA.

By regulating appetite and energy use, leptin has a fundamental influence on most key aspects of dairy and beef production. Classifying the type of leptin gene in beef cattle identifies those that will reach harvest weight sooner and develop more marbling.

Because IGENITY L tests for a specific DNA trait that doesn't vary, this new knowledge will help beef producers:

  • add value to breeding stock;

  • select sires of known genotype in commercial cow-calf breeding programs;

  • sort cows by genotype and match them to appropriate sires;

  • test or sell replacement heifers to improve beef quality;

  • buy or select feeder calves of similar genotype, frame score and age to finish them uniformly;

  • manage finishing rations to match genotype and earn market quality incentives; and

  • retain ownership of feeder calves of known quality.

“Do-It-Yourself” Sampling

In July 2003, Merial obtained exclusive rights to the leptin DNA test through a global marketing agreement with Quantum Genetics, Inc., of Saskatchewan, Canada. Merial has formed a new business unit to sell testing services directly to producers. Test kits will be sold through Merial sales personnel and online at www.igenity.com.

Producers supply animal hair samples for the test, and receive genotype information via e-mail or hard copy.

Dairy and beef cattle management recommendations will be provided to help producers apply what they learn about their herd through test results. A simple animal identification (ID) system is supplied with the test kits. Test kits contain animal record sheets to help keep track of tested-animal ID.

Merial says leptin testing, and other genetic testing services it will introduce, will provide significant benefits to dairy and beef producers, as well as food processors.

For the beef industry, the advantage could be in breeding and grouping cattle of similar type into uniform lots, managing them appropriately, finishing them at a uniform time and increasing end-product consistency.

Cattle producers wishing to produce more meat grading USDA Choice or better can breed animals of known genotype and feed them appropriately. Producers preferring to serve markets for lean beef can breed for and manage cattle to meet that goal.

Additionally, Merial says source-verified and branded-beef supply chains will also find leptin genotyping efficient and useful.

While leptin genotyping will help beef producers increase consistency in meat quality, cattle finishers and processors can therefore source more consistent batches of cattle. For food processors, increased consistencies in milk or meat quality helps them better meet their consumers' demands.

University of Saskatchewan researchers identified the specific area of the cattle genome that influences leptin production, and have published articles in scientific journals about this discovery.

The research that led to the discovery was funded primarily by the Agriculture Development Fund of Saskatchewan, with additional contributions from the Agri-Food Innovation Fund, the Canadian Cattlemen's Association, the Alberta Cattle Commission and the Canadian federal government.