Source:  MEATINGPLACE.COM, 9/14/09

Scientists at USDA's Agricultural Research Service and Purdue University say they have developed a line of laying hens that show less aggression than commercial birds.

The hens met industry standards for egg production but had lower mortality rates at 58 weeks of age without the need for beak trimming.

When housed in communal cages, the gentler birds had a 20 percent mortality rate, compared to 54 percent for a control group of hens and 89 percent for the commercial line, the researchers found.

ARS biologist Heng-wei Cheng and William M. Muir of Purdue University, both in West Lafayette, Ind., took into account the birds' competitive interactions in a communal setting when selecting the hens for breeding.

The researchers said most breeding programs in the past 50 years have focused on traits related to production. As a result, egg production has increased significantly, but mortality due to aggression and cannibalism among birds with untrimmed beaks has also increased about 10-fold, they said.

Cheng said the less aggressive behavior in the new birds may be due to a decrease in dopamine, a neurotransmitter that has been associated with dysfunctional behavior and inability to cope with stress.

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