Rights: The University of Waikato Published 16 March 2010 Download

Tim Hale discusses how transgenic cows are identified. He gives us details of the transgenic cow herd at Ruakura and discusses breeding strategies.

Questions to consider
Would you expect a transgenic cow to have transgenic offspring? What does this depend on?
Why is it important to demonstrate that transgenic cows do pass their transgene onto their progeny

Jargon alert
RFID stands for radio frequency identification.


A transgenic cow is a genetically modified cow, which is pretty much like a normal cow except it’s got some added DNA. So they are different from normal cows because they have altered gene function, but in terms of the look of the cows, they are just the same as a normal cow. In reality, the only way we know visually that it’s a transgenic cow is because it’s either got an ear tag that tells us the numbers or we scan it with an RFID reader that then identifies it through its electronic number that it’s one of our transgenic cows.

The oldest transgenic cow we've got is now 9 years old – she was born in October 2000 – and they were mated and calved first in 2003. So from 2003 on, we've had progeny of transgenics on the ground. Normally, transgenic cows have transgenic offspring, but depending on whether you mate them with another transgenic animal or whether you just mate them with conventional semen then has an impact, because if you use conventional semen, there’s a 50/50 chance that they will be transgenic or not – because every animal has 50% of the male’s genes and 50% of the female’s genes – whereas if you mate specifically with another transgenic animal, then there’s probably a three-quarter chance that you will have a transgenic animal and then a quarter not. And one of the aims of the programme is to show that the gene that is being transferred into the animals is actually stable in subsequent generations, so the mating process is designed to show that, yes, transgenic animals do pass the gene to their progeny.