Kiwi scientists have taken another step toward a potential future of genetically-altered, hypo-allergenic, high-protein milk.
In 2012, Daisy the genetically-engineered dairy calf made headlines around the world after researchers at AgResearch used a genetic intervention called RNA interference to target a particular cow milk protein known to be allergenic.
The team, led by Dr Goetz Laible, succeeding in proving they could knock down beta-lactoglobulin (BLG), which form large part of the allergic reactions two to three per cent of infants have to cow's milk.
But the breakthrough posed another big question: would the same genetic trait carry on in Daisy's offspring?
Laible and his colleagues are now confident it has, having monitored 12 female calves born at a contained Waikato facility in August 2015.
Milk was taken from the calves - born from eggs taken from Daisy, fertilised and placed in surrogate cows - through induced lactation.
Results showed no detectable levels of BLG - a finding the team expected would also be seen when the animals lacted naturally with breeding next spring.
"We'd wanted to demonstrate that the changes we had seen in Daisy were stable and could be transmitted to the next generation," Laible said.
"That's really what you need, otherwise you end up with just one animal and one generation having the phenotype or characteristics that you intended."
The scientists first tested the process in a mouse model engineered to produce the sheep form of BLG protein in mouse milk.
Using a genetic technique, microRNAs (short ribonucleic acid molecules) were introduced into mice to knock-down the expression of the sheep BLG protein, resulting in a 96 per cent reduction in the BLG protein in mouse milk.
They next produced Daisy, a female calf that was genetically engineered to express the same two micro RNAs, this time to target the BLG protein that is also a normal constituent in cow's milk.
They then hormonally induced Daisy to lactate.
The resulting milk collected from Daisy had no detectable BLG protein and, unexpectedly, also had more than twice the level of the casein proteins that also normally occur in cow's milk.
Laible said having just one founder cow to work with had made the project challenging; but achieving an initial result was exciting.
"From our experience and from what's in the literature, the [calves'] induced lactation is a very good representation of what will happen in natural lactation."
Yet this didn't mean we could expect a new line of hypo-allergenic hitting supermarket shelves any time soon.
There was much about the milk's functionality and potential benefits - along with any safety concerns or negative consequences for processing - that still had to be explored.
"And then we would need to have sufficient data to engage with regulators who could potentially move this towards a possible product."
In New Zealand, development of such food products remains restricted by tight regulations around genetic modification.
"But you have to start with a first step - and it's our hope that the results will continue to be promising."