Urine sensors attached to cows to help address waterway contamination issue

The urine sensors are attached to grazing dairy cows and take detailed measurements every time the cow urinates. Photo / Supplied

Urine sensors attached to cows are being hailed as a breakthrough in the battle to address the problem of nitrogen leaching.

AgResearch says it has developed world-leading sensors to better understand how nitrogen is being excreted by cows, and therefore how best to tackle the impacts on the environment.

The urine sensors, which have been a work in progress since 2010, are attached to grazing dairy cows and take detailed measurements every time the cow urinates, including volume and frequency - and crucially the concentration of nitrogen in the urine that can potentially leach into soil and waterways, and can cause damage such as algal blooms.

The benefit of the urine sensors is a much greater understanding of the behaviour of the cows, which can help develop techniques to mitigate the nitrogen leaching from farms, says AgResearch senior scientist Dr Brendon Welten.

"Other sensors exist around the world to provide data from livestock, but these sensors we've developed are unique in their ability to record nitrogen concentrations each time the cow urinates during grazing.

"We can learn, for example, how different species of pasture affect the amount of nitrogen excreted in urine."

AgResearch said in a statement the sensors weigh about 1.5kg, and attach to the cow by a harness connected to a lightweight cow cover. They record the data through the use of multiple instruments (temperature, pressure and refractive index), with data stored in a data logger that can be remotely accessed via a wireless network system.

The sensors had already been used in both the United Kingdom and Australia.

"The operation of the sensors is complex, and at this stage we are working towards offering the sensors to other researchers around the world to allow them to use the technology to make similar gains," Dr Welten said.

The sensors had played a part in important progress made in the Forages for Reduced Nitrate Leaching (FRNL) programme - involving DairyNZ, AgResearch, Plant & Food Research, Lincoln University, the Foundation for Arable Research and Manaaki Whenua (Landcare Research).

DairyNZ senior scientist Ina Pinxterhuis said: "The FRNL results clearly confirm the variability in urinary nitrogen excretion over the day, making it necessary to have many repeated measures. The sensors make this possible."

"It is also great to see that the options we examine to reduce nitrate leaching do result in lower daily urinary nitrogen excretion and lower nitrogen concentration – if not during the whole 24 hours of the day, at least for some parts. This information provides new options for management too."