Dr Sharon Woodward told a recent Farmers Forum at Woodville about the results of a three-year farmlet study of the value of mixed pasture species, done at a DairyNZ research farm in Waikato.
One finding is that mixed pasture species will reduce the amount of N released by a cow when it urinates.
The trial involved growing a mixture perennial ryegrass and white clover with other species such as lucerne, chicory, plantain and prairie grass. The latter was quickly ruled out as it didn’t perform but all the others remained.
“We were looking at it firstly from just a dry matter availability point of view, especially over the summer. We expected when we established those pastures that they would offer big benefits in summer and autumn. The other question was, when you feed mixed pastures to your cows, do you at least maintain milk production at the same level and not experience any losses?”
Woodward says they haven’t seen any decrease in milk production during a couple of the autumn periods and have actually seen a bit of an increase. “On one of the field trials we were running, the cows were on equivalent intakes, so we wouldn’t have expected to see much difference in milk production because it would only have been a quality issue. But when we had the cows indoors and they were able to eat ad lib, we did then see differences in intake and in milk production.”
Woodward says the cows on mixed pasture ate a little less (14.6kgDM) than those on conventional pasture (15.8kgDM). But despite eating less the cows on the mixed pasture were more efficient and produced more milk.
Pasture performance proved interesting. For example, in summer at the height of the drought the lucerne acted as a ‘shade’ for the ryegrass.
“You could see ryegrass still at a reasonable length and lush green, whereas the ryegrass in the standard pastures was a few cm high and brown and curled up. AgResearch scientist Katherine Tozer had been looking at ‘weedyness’. Her research showed that the weed population in mixed pastures is kept under better control than in the standard pastures and in our trial the weed populations are very very low,” says Woodward.
But for dairy farmers, the possibility that mixed pasture species result in less nitrogen being contained in the urine of cows offers some hope in areas where N leaching looms as an inhibitor to production.
