After studying thousands of commercial chickens, scientists discovered that birds on modern production lines are missing at least half of the genetic diversity their ancestors once had, making them more vulnerable to diseases such as bird flu.

Purdue University animal sciences professor and co-director of the project Bill Muir said it is hard to determine what is missing, but recent concerns over bird flu highlights the need to ensure that even rare traits, such as those associated with disease resistance are not totally missing in commercial flocks.

The findings by Muir and an international team of scientists are the result of a worldwide study of commercial chicken populations and were published in The Proceedings of the National Academy of Sciences.

The team, which also includes scientists from USDA and Siloam Springs, Ark.-based Cobb-Vantress, Inc., began to analyze the genetic lines of commercial chickens in early October in the first study to look closely at the genetic diversity of poultry.

Researchers studied about 2,500 birds and found that most of the genetic diversity in modern chicken was lost in the 1950s when wide-scale commercial production became common.

According to Muir, it is important to preserve non-commercial poultry and wild birds to protect their genetic diversity, and that interbreeding some of these birds into commercial lines might help protect the poultry industry.

He said this might be the key to help the industry cope with future challenges as traits such a disease resistance may be found among other birds.