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USA: Happy and passive means more productive animals (Purdue University)

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  • Pamela Rice
    [EXCERPT: ...in a new method for selecting passive livestock animals ... for better long-term productivity.... The new program enables breeders to have optimal
    Message 1 of 1 , Aug 4, 2005
      [EXCERPT: ...in a new method for selecting passive livestock animals
      ... for better long-term productivity.... The new program enables
      breeders to have optimal improvement in productivity.]


      August 2, 2005

      Happy and passive means more productive animals

      WEST LAFAYETTE, Ind. - Breaking up families can be sad, but in a new
      method for selecting passive livestock animals, that's a main
      ingredient for better long-term productivity, according to a Purdue
      University geneticist.

      The new breeding program, designed to get the best out of the
      animals, is the first major advance in classical breeding in 20
      years, said William Muir of the Purdue Department of Animal Sciences.
      By picking less aggressive individual animals from a broad range of
      families, the same breeding program can be used for hundreds of

      The new program enables breeders to have optimal improvement in
      productivity while minimizing the health risks associated with
      inbreeding, he said. At the same time, the program overcomes
      competition among animals for resources that often means less
      aggressive animals suffer from lack of nutrition and increased
      injury. In a group composed of both aggressive and passive animals,
      even those at the top of the pecking order are harmed from
      overeating, which wastes food because their bodies can't properly
      utilize the nutrition.

      "Genes not only control your own behavior but also impact others,"
      Muir said. "For instance, if my genes make me more competitive and
      aggressive, it almost always comes at the expense of someone else. If
      a pig or chicken rises to the top of the ladder by stepping on the
      shoulders, or heads, of others, then a breeding program doesn't make

      Muir, who previously researched and advocated a group-selection
      theory to obtain a kinder, gentler bird, refines this breeding
      approach in a study published in the current issue of the journal
      Genetics. In Muir's new plan, individuals are chosen for their
      passiveness based on equations that identify whether an animal is so
      aggressive that it will negatively affect its penmates' health and

      In the original group-selection program, families of animals that
      produced less aggressive animals were kept together. The unfortunate
      side effect is that such inbreeding can have dangerous genetic
      consequences, meaning the program could only be used for only a few
      generations. Muir's new breeding plan avoids the problems of

      Because animal well-being is an important factor in livestock
      breeding and because animals need to be housed in groups, not only
      can selecting for less aggressive animals increase productivity of
      individual animals, but also that of the group as a whole, Muir said.
      Muir calls this the associative effects of genetics.

      "It's important in a group setting that the animals' genes not have a
      negative effect on others," Muir said. "If one pig is aggressive, his
      genes are negatively impacting 16 pigs. So, if we select pigs or
      other animals that get along together, then we can have animals that
      grow well."

      In groups with aggressive animals that overeat, productivity of all
      the animals tends to decrease because the animals that eat more than
      required use the food less efficiently, meaning they waste food and

      "In terms of energy, you can waste energy by maintaining a pecking
      order," Muir said. "But if animals don't care about a pecking order
      and they get along, that energy is transferred to production. So,
      it's a winning situation."

      Muir has worked with pig breeders to establish this type of selective
      program but used Japanese quail in the current study to validate the
      practice. He chose the birds because they tend to be very aggressive,
      even cannibalistic. In addition, they were a good study model because
      they reach maturity in about six weeks, are easily tagged and bred so
      pedigrees can be maintained, and it takes little room and feed to
      breed and raise them.

      While beak trimming is used in some poultry breeding programs to
      minimize birds injuring each other, Muir's birds weren't beak trimmed
      so that their natural behavior could be observed.

      "In my quail experiment, we have definite data and facts showing how
      the birds react in different size groups," Muir said. "We could
      assess how much negative impact aggressive birds were having on other

      "Aggressive birds were causing a weight decrease in the other birds
      by 25 percent compared with birds housed in non-aggressive groups."

      Muir found that in just two generations of picking more passive
      quail, the flocks had a dramatic decrease in aggressive behavior and
      injuries. The study also showed that when classical breeding
      approaches were used, competition became worse and productivity
      declined, he said. The only way to solve this problem is through
      accounting for competition in the breeding program, as the new method

      This breeding program is easy to implement, requiring only that
      computer programs be used to define competitors and set up breeding
      and growth groups, Muir said.

      "This will enhance production traits that are influenced by
      associative effects while also improving animal well-being, which
      leads to a successful situation for producers, consumers and
      animals," he said.

      The old adage that athletes are born and not made may be even truer of animals.

      "If you're born with really, really passive genes, it will be hard
      for you to become nasty and aggressive," Muir said. "Animals don't
      have the ability to see into the future and decide that 'if I'm
      really aggressive, I can get ahead.'"

      Muir's study also examines genetic benefits that can be obtained by
      using the theory to track productivity in plants. This is evident
      when documenting the performance of trees where larger trees and
      certain types of trees have competitive advantage for nutrients and

      "Researchers recognized this in tree breeding even before plant
      breeding," Muir said. "They have often seen it when they thinned a
      stand of trees, it had much better yields. The key to making this
      system work for increased productivity is tracking the pedigree of
      plants and animals to know which ones are most likely to be passive."

      Muir also is director of the Molecular Evolutionary Genetics Graduate
      Training Program.

      Writer: Susan A. Steeves, (765) 496-7481, ssteeves@...

      Source: William Muir, (765) 494-8032, bmuir@...

      Ag Communications: (765) 494-2722;
      Beth Forbes, forbes@...
      Agriculture News Page

      Note to Journalists: A copy of the study is available by contacting
      Susan A. Steeves at (765) 496-7481, ssteeves@....
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