USA: Happy and passive means more productive animals (Purdue University)
- [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
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
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
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@....