Balancing Feed Demand and Pasture Recovery After Drought
In my travels I get to see a range of pasture management strategies used to come out of the drought.
These vary hugely, from long rotations of up to 60-plus days and as short as 18 to 20 days. Such a big disparity – who is going to get it right?
The advice is certainly biased towards the longer rotation but I cant help wondering if this is good advice or just a storyline that is repeated each year without some real thought into important pasture management and feeding principles?
Let’s explore:
Pasture management
The better we can care for pastures the faster will be their recovery for winter. If we can hold residuals as high as possible through the drought and after we can achieve the following:
Less pasture pulling – stalk and stem sits low in the pasture and is resistant to snap, so cows just pull it out of the ground. Grazing above the resistant layer will leave more of the pasture intact with the soil.
Higher residuals mean more plant reserves, helping the plant recover quickly from grazing.
New seedlings and tillers are emerging at a fast rate as the soil moisture lifts and while the soil is warm. Grazing at a higher level will allow survival of the new plants leading to much denser winter pasture.
Higher grazing levels indicates a higher intake for the cows. Happy cows, more settled and less prone to damaging the pasture.
Easy to say, but how can we achieve this
Managing Intakes
If we can feed the cows well then it is possible to operate with higher pasture residuals in all but the worst of droughts. Holding onto pasture cover for as long as possible will allow a greater proportion of the diet as pasture. To do this it is vitally important to hold pasture feed demand kg dm/ha/day close to grass grown or below.
We can do this by maximising the amount of supplement fed, within economic limits.
Reducing feed demand by reducing cow numbers early and incrementally – my advice is 5% to 10% of cows at a time and review every 10 days. If the drought holds for longer then all culls will be gone. If it rains in the meantime there is still a good number of cows to milk through to autumn.
Work out what allowance of total intakes is required for the herd to keep milking and to hold/gain condition. Set an acceptable grazing residual. In spring this might be 1600. In the dry it could be that 1350 to 1400 kg dm/ha is all that can be achieved.
This will allow you to calculate the grazing area required to meet the grass intake requirements.
For example
Culls gone and down to 240 cows on 100 ha. Pregrazing cover is 1800 and residuals are 1400 in this case.
Supplements fed are 5 kg dm meal, 4 kg dm maize silage and 4 kg dm grass silage – 13 kg dm supplements. Total intakes required for weight gain and good production are 20 kg dm per cow offered – maybe 18 kg dm eaten.
So grass required is 7 kg dm per cow. Total feed required is 1680 kg dm. Feed available on the paddock is 400 kg dm/ha. Therefore in order to feed the cows well the area required is 1680 kg dm/400 kg dm = 4.2 ha grazed per day.Rotation length calculated is 100 ha/4.2 ha = 24 days.
Most importantly, the grass feed demand will be just 16.8 kg dm/ha/day. Relate this to the grass grown at the time. If it is above this, then all is good, and pasture cover will be lifting and being looked after. If it is below, then it is time to drop more cows out.
Summary
Rotation length is not the driver. In the above example if we extend the rotation the residuals will drop too low and it will be very difficult to achieve the required intakes. Production and cow condition will be compromised – as will pasture health.
Calculating required intakes and adjusting to keep feed demand at or below grass growth rates will result in better pasture, higher cow condition and a better production base to drive through autumn with.