I have just walked all our grazing block with the Plate Meter again this morning and I think I need to have a bit of a review of where we are at with the grass. I am trying to decide whether I should release six hectares of silage aftermath to the cows to graze.
There are a number of things I need to consider:
- Grass growth has slowed up a little – in part due to dry weather of late and in part due to seasonal slow down in growth at this time of the year.
- We are now three weeks since taking first cut silage and the aftermaths have recovered to a point where if we are going to graze any we need to do it now, or they will be too far forward.
- We have several acres of stubble turnips coming on nicely but they won’t be ready for another month.
- Some of the young cattle are getting a bit tight for grass.
When I measured the grass this morning I found that average field covers were at 2,152kg of Dry Matter per hectare on the current grazing block – a fall of 158kg from nine days earlier. However, if I now release six hectares of silage aftermath for grazing this will raise average covers to 2,233kg DM per hectare, giving me a total cover of 109,244kg DM on the extended grazing block.
So what does this mean in feeding terms?
We currently have 178 cows in milk and I estimate they are eating an average of 17kg of grass dry matter a day. So, my daily requirement for the herd is 3,026kg.
Grass growth is currently averaging around 70kg DM per hectare per day, but what will my grazing look like in two weeks from now if cow demand, the grazing area and grass growth rates stay as they are today? The table below shows how I have calculated this.
Table to show projected grass cover in 2 weeks’ time
|Current total cover on grazing block (kg DM)||109,244|
|Hectares in current grazing block||42.9|
|Average daily growth rate (kg DM / Ha)||70|
|Projected total grass growth over 2 weeks (kg DM)|
|42.9 Ha x 70kg x 14 days||42,042|
|Projected total cover in 2 weeks (kg DM)||151,286|
|Cow grazing demand over 2 weeks (kg DM)|
|178 cows x 17kg x 14 days||42,364|
|Total cover in 2 weeks time allowing for grazing demand|
|157,166kg – 42,364kg||108,922|
The above table illustrates that if I confine the cows to grazing the current block of 42.9 hectares, the total grass cover available to graze will almost remain static over the next two weeks, if grass growth rates remain at 70kg DM per hectare per day.
However, if I include the additional six hectares of silage aftermath in my calculation, the total projected cover in two weeks time will be 5,500kg higher than it is today. This translates into less than two days additional feeding, since daily demand for the herd is 3,026kg.
So, do I cut the six hectares of silage aftermath for a second time or do I let the cows graze it tomorrow?
I nearly added this same six hectares to the grazing block three weeks ago and then decided to cut it – largely because it had got too far ahead of the cows to be grazed down tightly. As it turned out, that was the right decision. We have kept the cows going on what we have. Now I have to make the same decision again but the current level of cover in that field is at 2,800kg DM per hectare today and I could graze it more effectively – if I act now.
This might seem like a lot of fuss over nothing but I do feel we have reached an important stage in the grazing season and the decisions I make now will determine how much we get out of grass over the next few months.
I have decided I am going to graze the silage aftermath this time around as I am afraid we might find ourselves tight for grazing in July and August if I don’t. If we leave the additional six hectares to cut again, it wont be available to the cows until early August. Although we have some stubble turnips coming along nicely they won’t really be ready to graze for another four weeks. So, if we have a dry spell and grass growth (and quality) declines, we could be in trouble. Besides which, I can always shut up the odd paddock and cut for round bales if we find we have a surplus in front of the cows a few weeks from now.
As I have said before, I am only a student at this grassland management thing and if you have any comments on my decision making process, I would be glad to hear them. In the meantime, make time to manage your grass and think more than a few days ahead to ensure you get the most you can from grazing.