CRV Ambreeds new research findings on nitrogen partitioning

CRV Ambreed identifies a relationship between milk urea and the percentage of protein in milk

CRV Ambreed’s latest research on how to reduce nitrogen leaching on New Zealand dairy farms has identified that a proportion of the nitrogen is diverted away from the cow’s urea when they are bred for low milk urea concentration and this goes into the milk protein. This finding further assures that when cows are bred for low milk urea concentration, it will not only reduce the amount of nitrogen excreted but will also increase the efficiency with which nitrogen is used for the production of milk protein.

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For decades, research has been conducted on how to make cows more efficient in the way they use dietary protein, and this new relationship identified by CRV Ambreed between milk urea and the percentage of protein in milk should provide scientists with new leads.

CRV Ambreed has begun with its marketing of semen from more than 20 high-performing bulls under the LowN Sires™ brand. These bulls, desirable for traditional traits, are genetically superior in their ability to reduce the concentration of Milk Urea Nitrogen (MUN) in their daughters.

There is international evidence of a direct connection between MUN— a measure of the amount of nitrogen contained as milk urea—and the amount of nitrogen excreted in urine when fed varying diets; cows with low MUN excrete less nitrogen.

CRV Ambreed’s research shows that it is possible to breed cows that genetically have lower MUN. These cows are expected to excrete less nitrogen and thus, thus less nitrogen will be leached into groundwater.  The dairy herd improvement company says that their calculations s show that a 20% reduction in leaching within 20 years is possible by using genetics to breed cows with lower levels of MUN.

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Further studies have indicated where some of the nitrogen goes when not absorbed into urea.

It is believed that this finding is a world-first in demonstrating variation between cows of differing genotypes for how they partition dietary nitrogen eaten in the form of protein.

According to CRV Ambreed R&D scientist Phil Beatson, dairy cattle convert nitrogen consumed into five areas:  milk (protein + urea), growth (muscle), dung, gases, and urine.

“Now we know that we can reduce MUN through breeding, and that these low-MUN cows will partition more dietary nitrogen from milk urea towards milk protein. This strongly indicates that low-MUN cows will excrete less nitrogen as urine because they divert some nitrogen away from milk urea and into milk protein,” Phil says.

He adds that modelling and genetic analysis of the LowN Sires™ bulls suggest about 25% of the nitrogen that will be diverted away from urine in their daughters will go into milk protein. A higher percentage of milk protein is good for milk processing companies that desire less water in the drying process.

Phil says that over the past 70 years, a huge effort has been invested to understand nitrogen partitioning and the latest discovery by CRV Amreed could just be the tip of the iceberg.

Phase 2 of the research will study groups of animals genetically different for MUN to understand more precisely the relationship between reducing MUN and reducing nitrogen in urine.

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