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.
Cattle considerations
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.
DAFWA research: Evaluation of dual purpose canola and cereals grazed with cattle
The grain yield of a wide range of canola and cereal varieties sown in mid April were unaffected by the grazing of cattle at a stocking rate of 20-22 dry sheep equivalent (DSE) per hectare (ha) for up to four weeks at Esperance in 2011. The grazed crops yielded the same as ungrazed crops sown at currently recommended times.
Aim
To investigate and demonstrate the importance of dual purpose crops (canola, wheat and barley) to improve the feed availability for cattle (in late autumn to early winter) in mixed farming systems of the high rainfall environment of Western Australia (WA).
Method
In separate paddocks (6.5ha) at the Esperance Downs Research Station we sowed one canola and one cereal experiment (Figures 1-4). The experiments were split plot designs with species and variety subplots randomised within grazing and time of sowing (TOS main plots) and three replicates. Dates of sowing were TOS1 = April 15 and TOS2 = May 18 and individual plots were 20m long x 1.44m. Yield was measured using machine harvest. The conventional/Clearfield canola blocks were treated as conventional canola and were sprayed with Lontrel and grass herbicide mixes, while RoundupReady blocks were sprayed with glyphosate at six-leaf stage only.
TOS2 plots were not grazed. Grazing of the TOS1 plots with cattle commenced on 15 June 2011 which was the earliest date allowable within the constraints of chemical withholding periods (e.g. Jockey treated canola seed). Grazing of cereals ceased four weeks later on 14 July, while the canola grazed plots were divided into two treatments – a short duration where grazing ceased on 4 July after 18 days (labelled two weeks), and a second treatment where cattle continued to graze until 14 July (labelled four weeks).
Stocking rates during the four week grazing period varied from 12–30 DSE/ha during the first two weeks of grazing as the grazing area available was manipulated to ensure adequate grazing pressure. The average stocking rate was 22DSE/ha for cereals and 20DSE/ha for canola.
Growing season rainfall in 2011 (April-October) was 358mm, slightly below the long term average (LTA) of 374mm. Winter rainfall in 2011 was below average at 121mm (LTA = 185mm) whilst October rainfall in 2011 was a record of 113mm (LTA = 43 mm).
Results
Canola
The majority of varieties handled grazing well, with similar yields to the ungrazed 1TOS treatments and ungrazed 2TOS treatments (Figures 1 and 2). Exceptions were 45Y22RR which lost yield if grazed for four weeks (but even then still produced 2.4t/ha - equal to any of the other Roundup Ready lines grazed for four weeks); CB Agamax which lost yield if grazed for four weeks compared to sowing later (2TOS); and Hyola 404RR which lost yield if grazed for four weeks but handled a shorter period of grazing well.
Cereals
Despite being grazed past stem elongation (Z30) the yield of cereals was not reduced by grazing for four weeks (Figures 3 and 4). In some instances sowing in mid April and grazing led to increased yield compared to sowing in mid-May (e.g. Endure, Wedgetail, and Urambie).
Preliminary analysis of yield component data indicates that while grazed cereals produced less biomass at maturity than ungrazed crops, they had similar number of heads, which filled to similar levels and subsequently grazed plots had improved harvest index. Record October rainfall is thought to have favoured the later maturing grazed plots.
Conclusion
Our preliminary analysis of the 2011 experiment indicates that a wide range of early sown canola and cereal varieties grazed by cattle maintained grain yield at Esperance in 2011. This confirms research conducted in other parts of Australia and experiences of growers who have adopted the practice in the region in recent years.
In WA we have extensive areas of crops sown from late April to late May and relatively low stock numbers (high crop to livestock ratio). As a result, we believe there is a need to determine how the mainstream crops sown in a more typical window (early to mid-May) recover from grazing as the opportunities for early sowing (March to mid April) are limited in many areas. It may be that lighter grazing (clip grazing) of more extensive areas is a better system to capture value from grazed crops for WA mixed farming systems.
An essential question is the level of recovery of crops from a wider range of grazing intensities (height/duration/time) sown over a wider range of dates (late April to late May) and at more locations with variable season length to better assess the potential for WA mixed farming systems.
DAFWA research: Cattle performance grazing canola and cereal crops
Cattle grazing cereal crops had a higher liveweight gain compared to the cattle that remained on the pasture. However 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. The highest growth rates for cattle grazing the cereal crops were achieved when the stocking density was 12 DSE/ha. The growth rate reduced as the stocking density was increased.
Aims
To investigate and demonstrate the performance of cattle grazing canola and cereal compared to animals left on pasture.
To investigate the value of spelling the pasture during the time the cattle are grazing crops.
Method
The performance of yearling cattle grazing crops for four weeks during winter was investigated in an experiment conducted at the Esperance Downs Research Station. This experiment was conducted in conjunction with an experiment assessing the impact of grazing, by cattle, on a range of varieties of canola, wheat and barley.
Twenty seven yearling heifers aged approximately 15 months with an average weight of 344kg commenced the experiment grazing pasture at a stocking rate of 9DSE per hectare. The heifers were then divided into three treatments; remaining on pasture (control), grazing canola or grazing cereals (a combination of predominantly wheat with some barley variety plots). Grazing of the cereals and canola commenced on 15 June for four weeks. Following this four week crop grazing period the cattle from the two cropping treatments returned to their pasture plots for an additional nine weeks until all treatment animals were slaughtered on 26 September.
Stocking rates during the four week crop grazing period varied from 12–30 DSE/ha as the grazing area available was manipulated to ensure adequate grazing pressure. The average stocking rate was 22DSE/ha for cereals and 20DSE/ha for canola.
Before being introduced to the canola and cereal crops the heifers were yarded for six hours and fed hay ad libitum to assist their introduction to the crop species. All treatments had access to hay during the four week grazing period at the rate of 1.5kg per head per day (hd/day). In addition the cattle in all treatments had access to a mineral lick supplement (Econovite™) for the four week grazing period.
During the 13 week period the cattle were weighed and assessed fortnightly for fat depth at the P8 site. The pasture plots were assessed fortnightly for feed on offer (FOO) (kg DM/ha) and botanical composition was assessed three times during the 13 week period. Both the FOO and the botanical composition were used to determine the impact of spelling pastures while the cattle were grazing crops.
Results
Liveweight gain
The liveweight gain of the cattle grazing the cereal crop was higher than that of the cattle grazing either the canola or pasture for the four week grazing period (Figure 1). The difference in liveweight carried through until the end of the experiment. However the only significant liveweight difference at the end of the experiment was between the animals that had grazed the cereal crops and the control animals that had remained on pasture for the entire thirteen weeks (Table 1). The growth rate of the cattle grazing the canola crop for the first two weeks was extremely low (0.04 kg/hd/day) as the animals adapted to the canola crop. However their growth rate improved (0.89 kg/hd/day) during the second fortnight of the four week period and was the highest of the three treatments for this two week period.
The cattle grazing the cereal responded well in the first fortnight of the four week grazing period achieving a growth rate of 1.41kg/hd/day. This growth decreased in the second fortnight to 0.67kg/hd/day as the grazing area was reduced to increase the grazing pressure on the experimental plots.
Final value of the cattle
Although the animals that grazed the cereal crops were significantly heavier at the end of the experiment compared to the control animals that remained on the pasture, this was not reflected in the carcass weights. The slightly higher average carcass weight seen in Table 1 for the cereal grazing treatment was not significantly different (P> 0.05) from the carcass weights of the other two treatments. This in turn meant that the difference in the average final value of the cattle from each treatment was also not significant.
| Treatment | Average gain during the four week grazing period (kg) | Average final liveweight (kg) | Average gain for entire 13 week period (kg/hd) | Average carcass weight (kg) | Average value ($/hd) |
|---|---|---|---|---|---|
| Cereal | 32a | 449a | 104a | 236 | 1004 |
| Canola | 13b | 438ab | 95ab | 233 | 998 |
| Pasture | 19b | 432b | 87b | 228 | 967 |
Values with columns with different superscripts are significantly different at P ≤ 0.05
Value of the spelled pasture
The difference between the feed on offer for the pasture plots that were spelled while the cattle were grazing either the canola or cereal treatments compared to the control treatment can be seen in Figure 2. At the end of the four week period the feed on offer difference between the spelled pasture plots and the grazed plots was only slightly higher at 120kg of dry matter per hectare, which was not significant. The difference in feed on offer became even less as the cattle grazed the pasture plots for the remaining nine weeks.
Conclusion
The lack of a significant difference between the final average dollar values of the cattle from the three treatments relates to the inherent variability of the dressing percentages of the cattle within each treatment. This may be overcome if the animals were grazed on the crops for longer than four weeks, particularly canola. It took two weeks for the cattle grazing canola to adapt to the change in diet (reflected in the poor growth rate) and they only benefited from the two weeks following this adaptation period. The results suggest that to achieve a benefit from grazing canola the grazing period should be greater than four weeks to overcome this poorer performance during the first two weeks.
The reduction in growth rate of the cattle grazing the cereal crop during the second two weeks of the four week grazing period corresponded to the increase in stocking density for this period. The stocking density was increased to impose adequate grazing pressure on the trial plots of the variety trial component of this experiment. This forced the cattle to consume more of the stem component of the cereal plants, leading to a reduction in the quality of the feed consumed. Higher growth rates in growing cattle grazing cereal crops may be achieved at low stocking densities where less of the total crop biomass is consumed.