Why it could be an expensive winter for dairy farmers if they don't get to grips with rotation plans
Building autumn covers of grass can be a tricky business.
If you don't build enough cows will end up eating too much expensive meals and silage in the month of October, and if you build up too much then you run the risk of leaving a butt of old grass through the winter which is a waste of good feed and will also impact heavily on next spring's grass quality.
Grass growth generally tapers off at the end of August, typically dropping below 60kgs growth per day, and it tails off further as we head into October, dropping to below 40kgs per day. Therefore the grass we graze in October/November has to be grown in September and this won't happen by accident. Table 1 shows the targets we need to be hitting for the month of August in terms of cover/cow and rotation length.
As you can see, the cover that is feasible to build is determined by the stocking rate on the milking block; however, the rotation length targets remain the same regardless of the stocking rate.
Rotation length needs to increase by two days per week from now on. Most farmers try to determine the rotation length by trying to remember when the cows were last in today's paddock, which gives a good indication.
However, a better approach is to divide the amount of ground the cows are eating on a daily basis into the total ground available. If you have 100ac available for the cows and they are eating 4ac per day, then your rotation length should be 25 days.
At the end of August they need to be eating only 3.3ac per day.
Adding two days per week to the rotation length can happen in two ways: increasing the supply of grass or by reducing the demand.