The emphasis in animal breeding is shifting from traits that are easy to improve, such as milk production and growth rate, to those like reproduction, longevity, disease resistance and robustness that are difficult to alter by conventional selection strategies.

The latter are inherited to a lesser degree; thus they do not rapidly respond to conventional selective breeding. Also, their measurement is time-consuming and expensive. As a result, genetic markers will play an increasingly important role in improving these traits in livestock.

Performance Genomics Inc. introduced its first DNA marker for reproductive longevity for use in swine to the market in early 2004. A major R&D effort is now underway to identify the remaining ones having a major effect on this economically important trait.

Market

The global animal production industry, with an annual livestock replacement cost approaching $100 billion, represents a significant market for breeding markers. Nearly 150 million breeding animals are required to produce the beef, pork, and lamb meat consumed annually in the developed world. Increasing the lifespan of these breeding animals will increase their output of offspring, thereby reducing the number of breeders required by producers.

Breeding markers provide the most economically efficient means of increasing the superiority of dairy and beef cattle, pigs, poultry, sheep, and aquatic species with respect to such traits as overall reproduction, longevity, and robustness.

DNA markers for reproductive longevity will benefit the global livestock industry. For example, as milk production is a reproductive function, increased reproductive longevity will reduce the replacement cost of the highly specialized animals used for this purpose. Approximately 30 million cows are required annually to maintain the developed world's dairy herd. New breeding markers provide a valuable means of increasing the superiority of these individuals with respect to such traits as overall reproduction, longevity, milk production, and robustness. For example, recent research by Strandberg in Sweden has demonstrated that an increase in the length of time in production from three lactations to four can increase milk yield per lactation and profit per year by 11% and 13%, respectively. Reproductive longevity is even more important in beef cattle, swine, sheep and fur-bearing animals, where replacement cost has, after nutrition, historically been the second highest source of expenditure.