NUEMARKER

Nitrogen isotope fractionation as a marker for Nitrogen-use efficiency in dairy cows

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 Obiettivo del progetto (Objective)

'This project will develop a simple diagnostic tool to assess the efficiency of conversion of feed protein into milk and meat protein by ruminants (N-use efficiency; NUE). It addresses the central issue of the relationship between valuable product (milk and meat protein) and waste (urine N, potential pollutant). It is pivotal to European objectives about increasing the supply of healthy, whilst also reducing the environmental effects of ruminant agriculture. The approach is based on measuring the differential fractionation of the stable isotopes of N (Nitrogen-14 and Nitrogen-15) in the metabolic pathways leading to milk or meat protein and urinary Nitrogen respectively. The tool will be used at the large-scale across a range of disciplines that are addressing these problems, including animal nutrition and both plant and animal genetics/genomics – contributing to future multi-disciplinary working. Initial work will develop understanding of dietary factors affecting N fractionation using controlled feeding studies with sheep. Treatments will be designed to alter independently a range of N metabolism pathways (protein degradability, microbial protein synthesis, urea recycling, hepatic ureagenesis and hepatic protein synthesis). We will then apply information about fractionation effects in the different pathways to develop a sampling and analysis protocol to relate isotope measurements to NUE in lactating cows, and ultimately free-grazing cows. The ideal outcome will be a test based solely on milk analysis, since this is easily collected. The project will support recruitment of technicians and postgraduates for the new Animal Bioscience Centre. It will promote the integration of the applicant into EU science through securing the future of the new research centre. I will assist in developing collaborations and student exchanges with centres in Europe, as well as extending useful academic and industry contacts with the New Zealand.'

Introduzione (Teaser)

A research project has made progress towards a tool that can measure how efficiently cows are using dietary nitrogen.

Descrizione progetto (Article)

Nitrogen-use efficiency (NUE) is a measure of how well cattle are able to convert nitrogen in their diet into milk and meat proteins. Optimising NUE in cattle will improve agricultural production while reducing environmentally unfriendly nitrogen waste products.

As part of the EU-funded 'Nitrogen isotope fractionation as a marker for nitrogen-use efficiency in dairy cows' (NUEMARKER) project, researchers were tasked with developing a simple diagnostic tool to measure NUE in ruminants, starting with cattle.

They studied both beef and dairy cows in Ireland and New Zealand, with varying types and quality of feed. The project used the variation in stable nitrogen isotopes to track nitrogen use in the animals.

Researchers showed this method to be a reliable way to measure feed efficiency compared to conventional methods. However, large amounts of rumen-degradable protein in animal waste products meant that a relationship between isotope fractions and feeding efficiency could not be established.

Despite this, NUEMARKER did find a strong relationship between the proportion of a particular nitrogen isotope (15N) in the blood and the feeding efficiency of both dairy and beef cows. Further, high NUE was associated with high breeding worth, a commonly used method to estimate the economic value of an animal or breed.

The NUEMARKER project laid the foundation for a simple new diagnostic test of NUE that does not rely on measuring food intake. This promises to improve the overall productivity of ruminant agriculture.