Plans to create turkeys that never become broody have ruffled more than a
few feathers in the US. Bernie Wentworth and his colleagues at the
University of Wisconsin in Madison say that turkeys could lay between 15
and 20 per cent more eggs if they did not lapse into periods of broodiness
when they want to incubate the eggs they have laid.
Jeremy Rifkin, director of the Foundation on Economic Trends, a pressure
group which opposes many uses of genetic engineering, describes the
experiment as the 鈥榤ost outrageous鈥� case he has heard of. 鈥業t鈥檚 an example
of further reducing the creatures to machines that can perform some market
function, but at the expense of destroying their natural behaviour
辫补迟迟别谤苍蝉.鈥�
Wentworth鈥檚 group hopes to genetically engineer turkeys so that they cannot
produce prolactin, the hormone that triggers broody behaviour. They have
already hatched chicks that carry an artificial stretch of DNA in their
sperm and ova which blocks production of prolactin. The 鈥榥onbroodiness鈥�
trait will not appear in these chicks but 鈥� if all goes according to plan
鈥� will appear in their offspring, which should incorporate the 鈥榖locker
gene鈥� in their chromosomes.
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鈥業 will make this an issue,鈥� says Rifkin. He promises to start a consumer
boycott of any eggs laid by the genetically engineered birds. 鈥楾his is a
serious violation of the intrinsic value of the creature. It鈥檚 ethically
unconscionable.鈥� He argues that increasing the number of eggs a turkey lays
is not a desperate national need.
Wentworth says it is possible that people will boycott the turkeys, 鈥榖ut we
are just trying to see if it can be done鈥�. At present, he says, farmers try
to shock birds out of broody behaviour by exposing them to bright lights or
by making them stand on wires so they are unable to settle.
Some people fear that the introduced trait will spread to wild turkey
populations, says Wentworth. But he doubts that this would happen because
birds carrying the 鈥榖locker gene鈥� would not pass on their genes because they
would not incubate eggs.
Wentworth has made an 鈥榓ntisense鈥� fragment of DNA which sticks to the gene
responsible for prolactin, preventing production of the hormone. He
introduced the fragment into laboratory cultures of germ cells from a newly
fertilised turkey embryo. Then Wentworth injected the transformed germ cells
into the veins of turkey embryos. Once in the bloodstream, the cells migrate
to the gonads where they multiply, becoming sperm or egg cells.
The engineered chicks will be tattooed, banded and raised in secure pens
behind double-locked doors at the university鈥檚 Arlington Agricultural
Research Station.
