Although grazing crops has a long history, it is becoming more common to see sheep grazing oat, barley and even wheat crops at this time of year.
Research undertaken through the Grain & Graze 2 initiative and funded by the GRDC, has shown that it is possible for cereal crops to be grazed without negatively impacting yield.
There are, however, a few factors growers need to consider before opening their paddock gates to sheep.
When to start grazing
Grazing can commence once plants have ‘anchored’ (have nodal roots at the plant base).
To test if crops are ready for stock, growers can use the twist test which simply involves pinching the top leaves of the plant, twisting and pulling upwards.
If the leaves break off and the plant does not pull out of the ground then the crop can be grazed.
In fact, if anchored, plants can be grazed as early as the three to four leaf stage but the seasonal conditions should also be first considered.
Dry conditions and a hard compaction pan can sometimes inhibit root elongation, tillering and, indirectly, nodal root development. These plants may be pulled out during grazing which will impact subsequent feed and grain production.
Grazing intensity
The lower a crop is grazed, the longer it will take to recover leaf area.
It is recommended not to graze below the ‘white line’ (point where stem goes from green to white) but if the season is expected to be short, it is best to leave some green leaf.
Higher stocking rates will help achieve more-even grazing, reducing trampling, the risk of baring out areas and uneven ripening. Use of electric fencing and frequently shifting stock can help achieve this.
Grazing duration
If the crop is for forage only, rotationally grazing two to three times will keep the crop more nutritious (higher energy and protein, lower lignin) compared with set stocking.
If a crop will be used for hay or grain production, then it is best to graze early, but not past growth stage 30 (end of tillering).
Leaving some green leaf will support the plant recovery process while longer or later grazing can delay maturity.
Early sown crops will recover best after grazing.
Animal health considerations
A change in diet and high water content may result in scours.
To avoid this ensure the new feed source is introduced slowly and provide roughage such as hay for one to two days before introduction and continue while on the cereal crop.
Grazing green oats, wheat or rapidly growing grasses can induce milk fever (hypocalcaemia). In sheep it is usually seen in ewes in late pregnancy but can be seen in all classes of animals.
Farmers grazing wheat crops should also try to avoid low magnesium (Mg) which may result in grass tetany (cattle) or grass staggers (sheep), or subclinical deficiency, such as lower growth rates (hypomagnesaemsia) under more marginal deficiencies.
A 1:1 mix of Causmag (MgO)/salt and sun cured hay will help protect animals from Mg deficiency problems.
The publication ‘Free Food for Thought’ discusses the effects of grazing crops on animal and plant production in more detail. Copies are available from BCG (5492 2787).
For more information on grazing crops phone Alison Frischke on 0429 922 787, email alison@bcg.org.au or visit the Grain and Graze website.
