Cow pee leaching solutions found

Diet, stocking rates and genetics can help reduce the estimated 1000 tonnes of nitrogen that New Zealand’s 4.8 million dairy cows leach onto paddocks every day.

The calculation from dairy genetics company CRV Ambreed is based on milk urea (MU) concentration data found in the bulk milk reports given to farmers from their dairy companies.

MU is an indicator of how much dietary nitrogen consumed by a cow as plant protein is not being used for milk production and is excreted.

About 20 per cent of the 1000t of nitrogen leached into soils and ended up in ground water, CRV Ambreed’s research and development head Phil Beatson said.

The average amount of MU excreted by a New Zealand cow was 30 units. If that cow excreted seven times a day, it excreted 210 grams of urinary nitrogen a day.

Beatson said talks with farmers showed that with good feeding, they were able to limit excess nitrogen in the cow’s diet.

‘‘At the low MU, we are talking 22-24 [units] and perhaps even lower, which indicates there will be less urinary N per cow.’’

On the other side of the spectrum, there were cows which had an MU of between 36-38 units.

‘‘I was surprised to see this amount of variation in the MU and certainly there are genetic effects as well.

‘‘It’s clear that there is variation that can be used through feeding and breeding to reduce MU.’’

Beatson said farmers with cows that had a lower than average MU tended to keep a close eye on the levels and feed their cows a diet of low crude protein.

‘‘They do that primarily by balancing pasture with maize or grain or something that has lower N but higher energy.’’

He is encouraging farmers who get bulk milk reports to use the information to determine what practices influence MU daily variations with an overall aim of reducing MU and therefore urinary nitrogen.

‘‘It seems to me that this piece of information is potentially really valuable for farmers to monitor what their herds are doing with regard to the amount of N excreting in urine.’’

MU data told farmers what the average cow was doing and, when combined with stocking rates, revealed how much N was hitting the ground, he said.

‘‘We have got to put this into perspective of stocking rate as well to get this urinary N hitting the ground. It’s not just the milk urea, it’s the combination of stocking rate that tells us how much.’’

DairyNZ strategy and investment leader for productivity Bruce Thorrold said the research highlighted the potential to breed cows for lower urinary nitrogen output.

DairyNZ had picked up this opportunity and was contributing to a seven year $21 million research project along with the Ministry of Business, Innovation and Employment, CRV and Fonterra. ‘‘Right now, the idea that breeding for low MUN (milk urinary N) will reduce urinary N is unproven – the research team including DairyNZ, AgResearch and Lincoln University scientists will test these ideas over the next few years and develop ways for NZAEL (New Zealand Animal Evaluation Ltd) to include MUN into breeding values for farmers and bull breeders.’’ Landcorp’s Rangedale Station has been confirmed as testing positive for Mycoplasma bovis.

The sheep and beef property near Pahiatua in North Wairarapa was confirmed as having the cattle disease by the Ministry for Primary Industries.

Landcorp (Pamu) spokesman Simon King confirmed the farm had tested positive for the disease and was working with MPI and local veterinary services and were currently culling the impacted herd. ‘‘We had been in touch with neighbouring properties to advise them of the potential that the farm was infected last week, and we held a community meeting on Wednesday to update our neighbours on the situation and the actions Pa¯ mu (Landcorp) is taking.

‘‘Testing on the farm was undertaken after National Animal and Identification Tracing (NAIT) records showed a connection with an infected property.

‘‘Once we became aware that we had purchased stock from an infected farm we began testing animals and self imposed an animal movement ban from the property.’’

It is the second farm in the North Island to test positive for the cattle disease.

The Ministry’s director of response Geoff Gwyn said the farm had been identified through tracing and its use of Nait records, and was connected to other infected properties through animal movements.

‘‘The farmer concerned has been very co-operative with movement controls and has not moved any animals off the property, except to slaughter, since even before legal restrictions were issued.’’

Rangedale Station is a 1578ha (1382ha effective) property and was the 2012 supreme winner of the Horizons Farm Environment Awards.