Wet Weather Grazing

Published 4 May 12

With some areas experiencing the wettest April since 1910 and unseasonably cold temperatures, grazing management has thrown up some challenges in the last few weeks.

Speaking at a DairyCo discussion group at Lydney Park, Glos, last week, Dr John Roche of Dairy NZ said "If you find yourself with a hole in your grazing wedge because land had been taken out for silage earlier in the season it is important to remember that the three leaf rule is crucial and not get tempted to enter paddocks too early.

"Provided soil temperatures are the same, each leaf on the grass plant should appear at the same rate but if you are going in at the two leaf stage you could be reducing potential pasture grown by 15-20%.

  • approximately 15% of the pasture is grown in the 1st leaf
  • 35% in the second
  • 50% in the third leaf

"A longer rotation means more grass by default. You are allowing the grass time to grow that valuable third leaf.

"With a lower stocking rate it is harder to manage that all important three leaf stage," Dr Roche explained. "You can either get tempted to go in too early to keep on top of things or wait until the three leaf stage to enter a pasture, and the grass can get away from you. You won't leave the right residuals (1500) and canopy closure will happen faster. A higher stocking rate means many of these decisions are made for you.

"Walk the pasture, pull out a few plants and check leaf emergence. Use it as another piece of information about your grazing," he suggested.

"It is better to reduce grass to the cows now to extend the grazing season grass allocation and offer supplements. This allows grass to recover an reduces problems later in the season," Dr Roche said.

"If you've had some heavy rain and the paddock looks poached up don't panic. In reality if the grass root is still in the ground and there is plenty of moisture the grass should come back pretty well. Give it a week, see how things are and maybe then think about doing something
later in the season."

Ways to graze fields better in order to reduce poaching

  • Graze from the far side of the field first. That way cows never walk over bare ground, where they will do most damage.
  • Don't feed buffer before the cows go out. Let the cows go out hungry, let them concentrate on eating and then get them in afterwards if you need to.
  • Remember how much water there is already in cows' feed when there are wet conditions, and bear this in mind when looking at access to water trough. One farmer at the group said his cows had drunk an average of 4 litres of water the day before (a very wet day) and 48 litres the day before that.
  • Think about a sacrifice track - it doesn't have to be that wide as cows will walk in single file. It may take a bit more time when they are coming in for milking but it is worth it.

Dr Roche continued: "A grazing farmer manages the grass, it's the cow that harvests it and does the job making the milk. Any grazing system is a compromise between managing the grass and managing the cows. We tend to be animal lovers and it can be hard to force the cows out on a wet day. It is easier to train the cow than the human!

"If it's coming up for mating and the grass DM is dropping due to the wet weather, and in fact weather is affecting intakes as well, don't get too hung up on feeding. It is amazing the little effect small changes in nutrition have on cows getting back into calf.

"In recent research looking at two groups of cows, one had its nutrition reduced quite severely and yet only saw a 6% reduction in conception rate, compared with the other group," he concluded.



John Roche

Dr Roche holds an honours degree in agricultural science, a master in grazing management and farm systems and a PhD in dairy cow nutrition. He i Principle Scientist of Animal Science at DairyNZ, New Zealand's farmer owned research, extension and education company and an Adjunct Professor of Animal Science at Lincoln University in New Zealand. As well as having held science research positions in Australia and Ireland, Dr Roche consults widely to dairy units across the globe and was a founding partner in pasture-based dairy farms in Missouri.

His company motto is 'Science into Practice', with his advice proven in science and road tested in commercial farm settings.