The discovery by CRV Ambreed scientists is thought to be a world first and has shown that breeding this trait in cows not only makes the animal more environmentally friendly, but boosts its milk production efficiency.
The dairy herd improvement company recently begun marketing semen from ore than 20 bulls bred for their ability to reduce the concentration of milk urea nitrogen (MUN) in their daughters under its LowN Sires brand.
An analysis of the LowN sire bulls suggested that about 25 per cent of the nitrogen being diverted away from urine in their daughters would go into milk protein, CRV Ambreed research and development scientist Phil Beatson said.
More milk protein is good news for milk processing companies wanting less water in the drying process when creating milk powders.
The low-MUN and high percentage protein genetic link could also help scientists understand how animals partition the nitrogen they are fed, he said.
“Animal nutritionists will be extremely interested in our finding as there have been decades of research into nitrogen-use efficiency.”
This latest discovery strongly indicated that low-MUN cows could excrete less nitrogen as urine because the animals divert some nitrogen away from milk urea and into milk protein, he said.
This meant the genetics can be used for environmental gains as well as increasing the efficiency of cows.
This discovery could be the tip of the research iceberg, he said.
“A huge effort has been invested over the past 70 years trying to understand nitrogen partitioning and that’s produced some interesting trends but nothing conclusive.
“Now New Zealand scientists may target groups of animals that are known to be diverse for MUN to investigate differences in how they partition dietary nitrogen.”
Breeding and feeding cows are different avenues to reduce nitrogen excreted as urine and together are expected to yield more gains for farming and the environment..
“In other words, genetic gains will add to gains from better feeding.”
The research may also have positive implications for the beef industry because it was likely that beef cows could also be bred for reduced MUN.
That could provide a huge marketing tool for New Zealand beef. However, that area of research still needed a lot more work, said Beatson.
Cows bred for lower levels of MUN are expected to excrete less nitrogen in their urine when they are grazed on pasture.
“It could potentially save New Zealand 10 million kilograms in nitrogen leaching a year within 10 years, based on the national herd number of 6.5 million dairy cattle.”
Farmers who started a breeding programme for low-MUN added another tool to their farming systems to manage nitrate leaching and could potentially reduce their nitrogen leaching by 10-12 per cent by 2025.
That was a saving with a minimal or no disruption to normal farm management.
The next stage of the research would see scientists study groups of animals genetically different for MUN to understand more precisely the relationship between reducing MUN and reducing nitrogen in urine.