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Grass normally hits peak growth during mid- to late-May across Ireland. As grass covers build, sward quality can quickly decline, as grass turns from leaf and starts to head out.
Once grass turns to stem and seed, it is much harder for cattle to digest. Daily liveweight gain will be reduced and milk yields in cows can also suffer.
As grass is a plant, all swards will turn to seed at some point during May or June. The goal for farmers is to manage swards, so that cattle can continue to graze optimum covers as often as possible, maintaining performance.
Hard work
Be under no illusion, it is hard work trying to keep on top of grass quality in May and June. It requires farmers to take action and remove surplus grass as silage, even if this means baling 5ac that only yields 15 bales.
It is also important to clean off grazing residuals as tight as possible, as well as sub-dividing paddocks with electric fencing to control grazing areas.
But if you stick with it, you will maintain high-quality swards for the rest of the year, which boosts weight gain in cattle.
Benefits
Take a group of 20 bullocks with a daily weight gain of 1kg on good-quality swards from 1 May to 1 September.
Weight gain over the outlined period is 123kg of liveweight. For a similar group of bullocks grazing heavy covers of stemmy grass and gaining 0.8kg/day, weight gain is 98kg over the same period.
Across the 20 bullocks, there is 500kg less liveweight to sell, which, at €2.20/kg, is worth €1,100 in sale value. Outlined are some tips to controlling grass growth during May.
1 Walk swards weekly
As grass growth increases, you need to walk swards more often. This ideally means walking grazing ground twice weekly, as swards can change quickly.
At the very minimum, you should walk swards at least once per week. This will let you gauge which fields are getting too strong for grazing, which paddocks need grazing immediately and where to target fertiliser.
2 Increase size of grazing groups
Where cattle went out to grass spread over the whole farm, it is now time to double up groups to increase grazing pressure.
Otherwise, grass will get ahead of all these smaller groups, meaning there is a lot more wasted grass on the farm.
By increasing the group size, cattle will be able to graze swards faster, which will help to keep grass under control.
With fewer grazing groups, you will also be able to work a rotation and close off paddocks with surplus grass for silage.
3 Temporarily reduce the size of grazing paddocks
Make use of electric fencing to split paddocks and reduce the size of grazing areas. This will help cattle clean off swards, leaving less rejected grass behind.
Cleaning out paddocks as tight as possible, which should be below toe height, improves sward quality in the next rotation.
By sub-dividing paddocks, you will have to move cattle more frequently. But you will be better placed to gauge when paddocks can be closed for silage.
An alternative method to control grazing and increase grass utilisation is to strip-graze cattle. If you decide to go for this option, make sure to move animals at the same time each day, so animals do not run out of grass and break the wire.
4 Keep the rotation on track
Ideally, the grazing rotation should be around 14 to 18 days during May on productive swards. A 21-day rotation can be too long at this time of year, allowing grass to get ahead of cattle.
So, on a rotation with seven paddocks, this means cattle should be moving to fresh grass every second or third day. Do not be tempted to hold cattle for longer in paddocks because the sward has not been cleaned off.
By delaying the move to fresh grass, you are letting grass covers get even stronger in the paddocks ahead. It is better to move cattle on time, then top the sward, or graze it with ether dry cows or dry hoggets.
5 Don’t be afraid to skip paddocks
As grass growth increases, you can afford to skip paddocks where covers are getting too strong to graze.
This takes a bit of confidence to do, especially if it’s your first year grazing paddocks.
This is where temporarily sub-dividing paddocks works well, as you have more grazing divisions, making it easier to see where there is surplus grazing.
6 Take out surplus grass early
Once surplus grass has been identified, it is important to go in early and bale these swards. Cutting early will leave a green aftermath. This speeds up regrowth, meaning paddocks will come back into the next rotation with high-quality grass.
Delaying cutting date just to let grass bulk up means the aftermath will be white and much slower to recover. This could leave you tight for grass next month.
7 Topping grass
Where cattle cannot clean out covers tight to the ground, you will need to top rejected grass during May and June.
Using a disc mower is much more effective than a topper with a flail or rotary blade, as it leaves a cleaner aftermath.
In some cases, where there is a lot of grass to top, it is a good idea to mow the day before cattle are due to move to fresh grass.
This way, cattle will tend to eat the mowed grass, leaving less to decay on top of the sward.
8 Pre-mowing
An alternative to topping is to pre-mow heavier covers before grazing. It is time-consuming and as cattle will eat a higher percentage of stem compared with actively grazing, weight gains can dip.
But it is a short-term fix over three to four weeks to manage grass. The big positive is that it will increase grass utilisation and leave a clean aftermath for fresh regrowth.
9 Set-stocking
In set-stocking grazing systems, you can still manage grass quality. Mow one-third of the field every week to 10 days from mid-May to mid-June.
This will keep fresh grass coming in the sward and control the areas of the field where swards have gone to seed.
10 Apply fertiliser a little and often
While grass growth may be running ahead of cattle, it is still important to apply fertiliser in smaller but more frequent applications.
Nitrogen will help keep swards in a vegetative phase, where they develop leaf, rather than a reproductive phase when the plant turns to seed.
Spreading 15 to 25 units/ac of nitrogen after each grazing, or when swards have been topped, will maintain grass growth.
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