Why graze crops?
Both cereals and canola can be grazed by livestock and, with careful management, go on to produce acceptable yields. Studies have shown that on mixed farms, utilising crops for grazing can potentially lead to a whole farm increase in gross margins.
At the break of season, most crops germinate and produce a larger amount of biomass more quickly than pastures. This biomass can be used for grazing livestock whilst the crop plants are still in their vegetative state. Pasture paddocks will benefit when livestock are removed as pasture will have time to germinate and establish without being grazed. Pastures can be left to grow and develop a ‘feed wedge’ to use for feed during winter when livestock are removed from the crops.
The livestock enterprise can benefit from reduced supplementary feed costs when cattle graze on crops and the pasture wedge during the autumn-winter feed gap.
Animal production may also be higher if crops grazed have a higher nutritive value than feed that would otherwise be on offer during winter. This may enable stock to reach target markets earlier than would otherwise occur.
Cattle should not be introduced to lush pastures or crops on an empty stomach. Feeding with hay is recommended prior to introducing cattle to crops. A source of fibre should also be supplied when cattle are grazing crops. Mineral supplementation including magnesium, calcium and salt may also be required. Cattle, especially young stock, should be vaccinated against pulpy kidney before being introduced to lush paddocks.
Cattle require time to adapt to different sources of feed and be able to utilise it effectively. During this adaption period animals may not be able to gain the maximum nutritional benefit from the feed and animal performance may suffer. The Department of Agriculture and Food, Western Australia’s (DAFWA) research has shown that to see a significant benefit from grazing dual purpose crops, the grazing period may need to be longer than four weeks, particularly when grazing canola.
Early sowing is recommended to maximise biomass production for grazing. Seasonal conditions, such as a late break, can limit the potential of utilising crops for grazing. Stock should be introduced to the crop only when the plants are securely anchored in the ground and there is enough biomass available for the desired stocking rate. Any withholding periods on seed treatments should also be observed.
Stocking rates should be calculated to ensure enough grazing pressure to achieve an even grazing of the crop so that subsequent recovery and plant maturation remains even across the paddock.
To ensure limited effect of grazing on crop yield, stock should be removed by the beginning of stem elongation (growth stage Z30) or the beginning of bud formation in canola. Post grazing biomass, subsequent rainfall and growing season length can all affect crop recovery. Crops should be grazed to a level allowing enough residual biomass for plant recovery. The harder the plant is grazed, the longer it will take to recover.
Flowering times can be delayed by grazing. This can be advantageous as it may move flowering out of a frost window. However, if flowering is delayed too long this may push grain fill into a period of increasing temperatures and reduced moisture, affecting yield.
Reducing early biomass of plants through grazing can also mean ground water is reserved as less is needed to support biomass. The plant may be able to utilse this reserved ground water at grain fill improving grain quality.
Some compromise may be required when considering application of chemicals for the control of pests or weeds on the crops as withholding periods for stock need to be observed. Any nitrogen applications should be applied after stock are removed.