Cattle genes provide a pathway to reduced nitrate leaching

Nitrate reducing forage plants and bacteria, denitrification walls and now nitrate-busting bulls are being developed to lower farming's impact on the environment.

Thanks to an international breakthrough by dairy herd improvement company CRV Ambreed, bulls have been identified that pass lower nitrate levels through their urine onto soils.

The company has selected bulls genetically superior for a trait related to the concentration of urea nitrogen in milk.

A team of 25 bulls was identified with the genetic makeup for low concentration of milk urea nitrogen (MUN), including 10 each from jersey and friesian breeds and five kiwi cross sires.

In line with overseas studies, principal geneticist Philip Beatson has found bulls that will breed daughters with the desired low levels of MUN.

Selecting dairy sires with breeding values for lower milk urea nitrogen will potentially produce progeny that excrete 3.2 kilograms of less nitrogen/cow/year in their urine.

The breakthrough promises to reduce the amount of nitrates excreted in urine and therefore reduce its leaching on farms by 20 per cent within 20 years. This will result in a more sustainable dairy industry and take the heat off dairy farmers increasingly pressured to play their part in cleaning up waterways, says Beatson.

"If the connection between milk urea nitrogen and urine nitrogen 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.

The team of 25 bulls identified with lower MUN breeding values than average unselected bulls is being marketed this year as LowN Sires.