Grass+Dairy: predicted growth slows as cold spell forecast

When the grazing season began, many farmers on dryer soils would have targeted to start the second rotation on 1 April (plus 10 to 14 days on wet/cold soils). Although it has been a challenging start to the season with mixed weather conditions, many persevered with grazing.

If you have over 50-60 per cent grazed it is now time to stop and reassess the situation.

When to start the second rotation?

At this stage you should be walking the farm weekly to assess grass growth. When the first three to four paddocks grazed this spring have a cover of 1,200kgDM/ha its time to start the second rotation. Starting the second rotation at the correct time will ensure good quality grass is available for cows and cattle alike.

How do I predict the start date for the second rotation?

For example, if your first paddock grazed this spring has a cover of 800kgDM/ha on it today, this means we are 400kgDM/ha below where we want to be to start the second rotation. Use your current growth rate for your farm or the predicted growth rate in your area from the map on the right. If the average growth in your area is 25kgDM/day this means it will take 16 days for your first paddocks grazed to get to 1,200kgDM/ha. Add 16 days to today’s date and that is your planned start of the second rotation.

You should then carry out a grass budget on PastureBase Ireland to ensure you have enough grass to get to the planned start of the second rotation. If you don’t use silage or concentrate to reduce demand and slow down the rotation.

The dry weather over the last week has set us up nicely with super grazing conditions and we are hitting residuals of 3.5cm. We have 48% of the farm grazed to date. We will have 70 units/acre of nitrogen out across the whole farm by the weekend. Growth has been increasing steady and last week we grew 20kgDM/ha/day. The silage ground has got 2,500 gallons of slurry and 80 units/ acre of urea. We are still having issues with the SCC which is currently 266 and we have very few clinical cases showing up. The maiden heifers were let out to grass last week and are all on target weight.

I have 70% of the farm grazed so far and I am monitoring my grass budget to see when my second round will start. Im feeding 5kg of concentrate at the minute but this will be reduced depending on grass availability for the remainder of the rotation. The first paddock grazed in the spring has a cover of 850kgDM/ha. I targeted light covers, dry paddock and used on/off grazing, backing fences and spur roadways in order to keep the cows out during the wet spells of weather. At the moment while the weather is dry we are grazing heavy covers 2,000kgDM+ and will return to lighter covers should the weather change this coming week.

We started calving on the 26 January and have 92% calved. Grazing this spring has been challenging as the ground here does not take rain well. We started grazing on the 28 February and were back in full time for five days during the wet weather. We currently have 59% of the farm grazed. Last autumn we closed with a lower farm cover than usual to try something new as grazing heavy covers in the spring can be difficult. So far this is working well and graze outs have been excellent. The herd is made up of 50% first and second lactation. We estimate intakes are around 19kgDM made up of 10kgDM grass, 6.5kgDM concentrate and 2.5kgDM silage.