The colour of New Zealand's cattle herds is changing, and it's all because of fat.
Fawn-coloured Jersey cows produce more fat in their milk than black and white Holstein Friesians, and farmers are getting paid more for fat because consumers no longer believe it's so bad.
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Farming experts expect that to result in Jerseys taking over the bloodline.
"All cows produce fat in their milk, but Jerseys do produce more - that's what they're renowned for," says Alison Gibb, the president of Jersey NZ.
Ms Gibb been farming Jerseys since they were last in vogue, roughly 40 years ago.
"This is a very wet farm, so of course they are a lighter footprint on this soil type," she says. "They're a curious, friendly animal and they produce well."
Then came the 1950s and 1960s, when saturated fat was established as an enemy of public health. Consumers didn't want fat in their milk and farmers were paid more for protein.
Now consumers want fat again, on the back of recent trends such as the paleo diet - and dairy companies are responding.
Eight years ago fat was worth 30 percent of the payout. Now it's double that, and industry experts predict that the trend will continue.
Professor Keith Woodford says there'll be a gradual transition of farmers choosing to introduce more Jersey into their bloodlines.
"The colours of the cows are likely to change - it'll occur slowly."
Professor Woodford says farmers won't get the full price signals for another one to two years, but they'll see the trend and will need to make a decision as to what bull to use. From then, it'll be nearly three years before the colour change comes through into the milking herd.
This trend is all down to the consumer.
"Consumers have said rightly or wrongly that butter's back in favour, so the price of butter is at an all-time record," Professor Woodford says.
But health experts say consumers are wrong, and not all fat is good.
"Butter is pure, unadulterated saturated fat - and saturated fat is the main cause of heart disease," Rodney Jackson says.
The University of Auckland health science professor believes the fat fad won't last.
"The whole high-fat, low-carb dietary fad is moving away from the bad fats," Professor Jackson says. "Bad fats" are saturated fat - such as butter, cream and coconut oil.
But whether they're right or wrong, consumers drive the market - and as long as fat's in fashion, so too is the brown cow.