WEST LAFAYETTE, Ind. - Breaking up families can be sad, butin a new method for selecting passive livestock animals, that's a mainingredient for better long-term productivity, according to a PurdueUniversity geneticist.
The new breeding program, designed to getthe best out of the animals, is the first major advance in classicalbreeding in 20 years, said William Muir of the Purdue Department ofAnimal Sciences. By picking less aggressive individual animals from abroad range of families, the same breeding program can be used forhundreds of generations.
The new program enables breeders to haveoptimal improvement in productivity while minimizing the health risksassociated with inbreeding, he said. At the same time, the programovercomes competition among animals for resources that often means lessaggressive animals suffer from lack of nutrition and increased injury.In a group composed of both aggressive and passive animals, even thoseat the top of the pecking order are harmed from overeating, whichwastes food because their bodies can't properly utilize the nutrition.
"Genesnot only control your own behavior but also impact others," Muir said."For instance, if my genes make me more competitive and aggressive, italmost always comes at the expense of someone else. If a pig or chickenrises to the top of the ladder by stepping on the shoulders, or heads,of others, then a breeding program doesn't make progress."
Muir,who previously researched and advocated a group-selection theory toobtain a kinder, gentler bird, refines this breeding approach in astudy published in the current issue of the journal Genetics. In Muir'snew plan, individuals are chosen for their passiveness based onequations that identify whether an animal is so aggressive that it willnegatively affect its penmates' health and productivity.
In theoriginal group-selection program, families of animals that producedless aggressive animals were kept together. The unfortunate side effectis 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 inbreeding.
Becauseanimal well-being is an important factor in livestock breeding andbecause animals need to be housed in groups, not only can selecting forless aggressive animals increase productivity of individual animals,but also that of the group as a whole, Muir said. Muir calls this theassociative effects of genetics.
"It's important in a groupsetting that the animals' genes not have a negative effect on others,"Muir said. "If one pig is aggressive, his genes are negativelyimpacting 16 pigs. So, if we select pigs or other animals that getalong together, then we can have animals that grow well."
Ingroups with aggressive animals that overeat, productivity of all theanimals tends to decrease because the animals that eat more thanrequired use the food less efficiently, meaning they waste food andenergy.
"In terms of energy, you can waste energy by maintaininga pecking order," Muir said. "But if animals don't care about a peckingorder and they get along, that energy is transferred to production. So,it's a winning situation."
Muir has worked with pig breeders toestablish this type of selective program but used Japanese quail in thecurrent study to validate the practice. He chose the birds because theytend to be very aggressive, even cannibalistic. In addition, they werea good study model because they reach maturity in about six weeks, areeasily tagged and bred so pedigrees can be maintained, and it takeslittle room and feed to breed and raise them.
While beak trimmingis used in some poultry breeding programs to minimize birds injuringeach other, Muir's birds weren't beak trimmed so that their naturalbehavior could be observed.
"In my quail experiment, we havedefinite data and facts showing how the birds react in different sizegroups," Muir said. "We could assess how much negative impactaggressive birds were having on other birds.
"Aggressive birdswere causing a weight decrease in the other birds by 25 percentcompared with birds housed in non-aggressive groups."
Muir foundthat in just two generations of picking more passive quail, the flockshad a dramatic decrease in aggressive behavior and injuries. The studyalso showed that when classical breeding approaches were used,competition became worse and productivity declined, he said. The onlyway to solve this problem is through accounting for competition in thebreeding program, as the new method does.
This breeding programis easy to implement, requiring only that computer programs be used todefine competitors and set up breeding and growth groups, Muir said.
"Thiswill enhance production traits that are influenced by associativeeffects while also improving animal well-being, which leads to asuccessful situation for producers, consumers and animals," he said.
The old adage that athletes are born and not made may be even truer of animals.
"Ifyou're born with really, really passive genes, it will be hard for youto become nasty and aggressive," Muir said. "Animals don't have theability to see into the future and decide that 'if I'm reallyaggressive, I can get ahead.'"
Muir's study also examines geneticbenefits that can be obtained by using the theory to track productivityin plants. This is evident when documenting the performance of treeswhere larger trees and certain types of trees have competitiveadvantage for nutrients and sunlight.
"Researchers recognizedthis in tree breeding even before plant breeding," Muir said. "Theyhave often seen it when they thinned a stand of trees, it had muchbetter yields. The key to making this system work for increasedproductivity is tracking the pedigree of plants and animals to knowwhich ones are most likely to be passive."
Muir also is director of the Molecular Evolutionary Genetics Graduate Training Program.
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