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Opportunities for cattle grazing canola

Research through the Graham Centre for Agricultural Innovation is providing information for livestock producers to make the most of grazing beef cattle on canola crops.

Lecturer in agronomy at the CSU School of Agricultural and Wine Sciences Dr Jeff McCormick said dual-purpose canola has the potential to fill the winter feed gap.

“Canola forage has high metabolisable energy and crude protein, so it has the potential to deliver high live weight gains in cattle,” Dr McCormick said.

“But there can be animal health issues for cattle grazing canola crops, including nitrate toxicity, polioencephomalacia (PEM) due to high sulphur levels, and bloat.

“Traditional thinking is to introduce cattle gradually to the crop to allow their rumen microflora time to adjust, but Australian farmers do not tend to have the time to move cattle on and off a paddock over a long adaptation period. Our research tried to determine what was a minimum requirement for an adaptation period was.

“The grazing trial of Angus heifers was carried out by CSU Bachelor of Agricultural Science Honours student Mr John Paulet in July 2018 and supervised by Dr McCormick and Dr Shawn McGrath from the CSU School of Animal and Veterinary Sciences.”

The trial examined four adaption techniques including immediate introduction to the crop and four- and seven-day periods of gradual adjustment.

“The heifers achieved average daily weight gains of one and three-quarter kilograms per day for the period of the experiment with minimal animal health issues across all treatments,” Dr McCormick said.

“The research found a lag phase in the growth of cattle in the first week after being introduced to the crop, regardless of the adaption method. But following adaptation the daily growth rate commonly exceeded two kilograms per day, indicating that canola needs to be grazed for at least a month to achieve maximum benefits.”

Dr McCormick said there’s significant potential for grazing canola if it is well managed. He has these tips for introducing cattle to the crop:

– Reduce pre-sowing sulphur fertilisers for grazing crops. The occurrence of PEM appears to be one of the most important potential health risks, and ammonium sulphate applied after grazing would supply sulphur to the crop if needed.

– Ensure cattle are well fed. Hungry cattle are more prone to health issues.

– Introducing cattle to the crop mid-late morning during the adjustment period will reduce risks of cattle gorging themselves. Cattle eat a large proportion of their daily intake early in the morning.

– Although this trial did not demonstrate any negative health problems, adjusting the animals over a period of time will reduce the risk of any negative outcomes. Start for two hours and increase by two hours every day, carefully observing if the cattle are eating the canola and if there are any health problems.

– The research found very low nitrate levels in the canola leaf as compared to the petiole, ensuring that that there are high forage levels available will allow animals to select the leaf and reduce the risk of nitrate toxicity.

– Provide hay in the paddock to allow cattle to select different forage. This will enable cattle to substitute hay for canola in the diet and increase dietary fibre levels.

– During the adjustment period the cattle need to eat the crop. If they are grazing fence lines or any other non-crop areas it is unlikely the animals have been adjusted.

The project was supported by a 2017 Graham Centre Research Centre Fellowship. Mr Paulet was jointly awarded the Agricultural Science Medal when he graduated in December 2018.

This article was first published in R4A.

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