With grass entering the reproductive phase and pre-grazing yields higher than usual on farms, many farmers have taken to pre-mowing paddocks ahead of the cows.
For some, pre-mowing is a common action, whereas others wouldn’t dream of pre-mowing a paddock in front of their cows.
Although pre-mowing improves the quality of the grass in the subsequent rotation – through eliminating stemmy grass from the paddock – it has many disadvantages and is usually associated with poor grassland management.
Pre-mowing not only increases the workload on the farm – through additional time spent on the tractor mowing these strong paddocks – but there is also a diesel cost that goes along with this.
Instead of these paddocks being closed for silage, they end up being pre-mown, resulting in less surplus bales being made.
Additionally, pre-mown paddocks which contain a high amount of poor-quality stemmy grass can have a knock-on effect on the bulk tank.
A further disadvantage is the loss of grass. A certain percentage of the cover will always be lost in the process.
Research
Research conducted by DairyNZ in New Zealand showed that paddocks which were pre-mown had both reduced pasture density and pasture grown, when compared to a paddock that was grazed.
The pre-mown paddocks were also associated with less silage compared to the grazed treatment. In New Zealand, this resulted in a greater requirement for imported feed.
The study also revealed no animal performance benefit from the pre-mown treatment versus the grazed treatment.
Pre-mowing paddocks will only exasperate the problem. If you continue to pre-mow you will continue to enter paddocks with a higher than target pre-grazing cover.
If the paddock is strong, instead of pre-mowing the paddock, it should be taken out of the rotation to try and get back to a target pre-grazing cover of between 1,300kg DM/ha and 1,400kg DM/ha.
