Genetics may slash N leaching

Angus Haslett and Phil Beatson of CRV Ambreed say the company has uncovered a genetic strain of cattle that produce less nitrogen in their urine.

CRV Ambreed has made a genetic discovery it anticipates will reduce nitrogen leaching on farms by 20per cent within 20 years.

In what's thought to be a world first, the dairy herd improvement firm has announced it will market bulls which have a genetically superior trait relating to urea nitrogen in milk.

It is now selling semen from bulls whose daughters will have reduced concentration of Milk Urea Nitrogen (MUN) under the LowN Sires brand.

MUN is a measure of the amount of nitrogen contained as milk urea, and CRV Ambreed R&D manager Phil Beatson says there's overwhelming international evidence of a direct link between MUN and the amount of nitrogen excreted in urine when fed different diets.

"If this connection carries over, cows bred for lower levels of MUN are expected to excrete less nitrogen in their urine which will, in turn, reduce the amount of nitrogen leached from grazed pasture," he says. "[This] could potentially save New Zealand 10 million kilograms in nitrogen leaching a year, based on the national herd of 6.5 million dairy cattle."

He says projections indicate that it's possible to breed cattle that will reduce nitrogen leaching by 20per cent within 20 years.

CRV Ambreed has been researching the link between MUN and nitrogen in urine for five years and has now identified more than 20 existing, high-quality and top-performing CRV Ambreed bulls with the desirable genetic make-up for low levels of MUN. Hundreds of thousands of straws of semen are now available from the LowN Sires team.

"It's exciting news for farmers, the potential that they can help meet their environmental compliance through breeding."

Ambreed has analysed the MUN concentration in 650,000 milk samples to understand what is inherited, and to create a MUN value for all animals.

Mr Beatson says farmers who already herd-test and herd-record with CRV Ambreed will automatically get the MUN values of their cows from June. This will help with decisions around culling or keeping cows for AI using bulls with good MUN values.

Farmers who begin to herd-test and herd-record with Ambreed from June 2017 will have their herd's MUN values by the end of the year.

Managing director Angus Haslett says farmers are urged to start the journey to greener cows now as improved offspring will be born in 2018 and will have their first lactation in 2020.

He says that, while a vast amount of research is being conducted in NZ to mitigate nitrogen leaching, it makes sense to breed cows that produce less nitrogen in their urine from economic and environmental viewpoints.

"We know farmers are doing everything they can to mitigate nitrogen leaching and meet environmental compliance levels. The beauty about the genetic approach is that it has an additive effect to other strategies a farmer might be taking to reduce nitrogen leaching."

Mr Haslett says further research is required to confirm the genetic development and CRV Ambreed is working with DairyNZ, AgResearch and Lincoln University on this.

DairyNZ strategy and investment leader for productivity Bruce Thorrold says the
genetic breakthrough would give farmers in nitrogen-limited regions more options to reduce N-leaching without going away from a pasture-based system.