Farm Ireland

Sunday 21 April 2019

Scoffed at by traditionalists Zero grazing is now becoming increasing popular

Zero grazing is an increasingly popular option, especially during the unpredictable Irish spring weather

The AB 70 is designed to feed 60-100 cow herds
The AB 70 is designed to feed 60-100 cow herds
Derek Casey

Derek Casey

Last week's weather has done wonders for soil temperatures with grass now starting to jump out of the ground. But some areas will take a long time to dry out properly after all the rain we had in early March.

Around this time of year zero grazing machines are being used by many as both a grass management tool and a way of avoiding land damage in fields that remain susceptible to poaching.

These machines were scoffed at by traditionalists when they hit the ground proper around ten years ago. However, in the interim farmers up and down the country have bought them in numbers.

These machines tend to suit farmers with fragmented farms (avoids having to walk cows long distances) or on heavier land - particularly at times such as now, in the shoulders of the grass growing season when growth rates are not yet sufficient to meet demand. Most tend to use them at certain times of the year, but there are some farmers that zero graze year round.

Opponents of zero grazing claim it goes against the natural system of letting cattle graze outdoors, and can make cattle unfit. Some definite disadvantages of zero grazing are the added building, diesel and machinery costs, as well as the extra slurry storage requirements required. The farmer needs to ensure he has the infrastructure to support this approach.

Extra volumes of slurry will need to be spread, as well as the added daily job of actually going out to cut and collect grass. Extra machinery costs must be considered as well.

Replace worn cutting knives at the start of the season to ensure a clean cut and faster regrowth.
Replace worn cutting knives at the start of the season to ensure a clean cut and faster regrowth.

I got a chance recently to see an AB 70 Zero Grazer in action, kindly supplied by Niall O' Reilly of Zero Grazer, based in Cavan, who pioneered the system in Ireland over ten years ago.

This machine is a bit of a classic and would be a hit with dairy farmers who want a no frills unit capable of delivering grass to the 100-odd dairy herd. It cuts down to about 6cm using two drum mowers and takes a six foot wide swath. It has a 28 cubic metre capacity. The drum mowers are similar to what you would see on a hay mower, as pictured.

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The cutting height can be adjusted with a hydraulic ram controlled by one of the tractor's spool valves. Once the grass is cut it is then picked by tines on a reel that lifts the grass into the trailer body of the zero grazer.

In terms of tractor size needed, the guidelines for a machine of this size state that around 90hp is enough; during cutting the tractor doesn't need to be overly stretched and can operating at around 1400rpm max. In hilly ground and for road haulage, another 20hp is always a comfort but for a centralised farm you could manage with less.

Check the tension on the floor and elevator chains a part of a maintenance program.
Check the tension on the floor and elevator chains a part of a maintenance program.

Dos and don'ts

To get the best out of your machine and prolong its working life Zero Grazer advise on a number of operating tips. Before starting you need to check that the mower drums are level with the ground on both sides; this is done by adjusting the top link on either side.

A spool valve drops the cutting drums to ground. It is recommended that you always put the mower down first before engaging the PTO.

Turn on the PTO slowly if possible as this helps to gently ease the mower on, making it easier on the tractor and slip clutch on the drive shaft. Once on you can increase the tractor's revs. The next step is to move forward and move the drawbar out into cutting position via another spool valve.

In practice, the zero grazer doesn't follow the tractor directly but is offset by about six feet to the right via a spool valve for the drawbar. This ensures the zero grazer isn't trying to cut grass that has just been flattened by the tractor's wheels. During cutting it is best practice to allow grass to build up in the front of the trailer body and then move the floor rearwards as the load builds.

The floor is controlled with a third spool valve, and will usually need to be moved about ten times in order to fill the trailer properly.

A common mistake here is that farmers try to overload the trailer and squeeze in a huge load. This puts pressure on the floor chains and slats as well as the elevator that takes the cut grass up into the trailer body.

Excessive left or right turns will wear wide angle shafts. When turning right it is good practice to tuck the drawbar gradually back in behind the tractor, allowing machine to follow tractor. This will keep the tractor's wheels away from the drawbar and PTO shaft.


When the load is full the correct next step is to move the drawbar back in, leaving approximately three inches on the ram. To reduce pressure and wear on the drums and machine be sure not to lift the mower when the zero grazer is in the offset position. With the drawbar back in, it is safe to lift the mower drums and slowly reduce tractor revs before turning off the PTO.

During unloading it is recommended to put a small rev on the tractor. Open the door and move the floor rearward via the spool valve. The zero grazer floor has chains and angle iron slats that move rearward when activated with a hydraulic pump. These slats push the grass load out of the back of the trailer. If on a feedlot, you can slowly drive forward, allowing the grass to fall in front of cows.

With the load empty it is important to clean off any grass that is stuck on the latches of the trailer door and close the door properly to prevent waste from the next load.

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