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Published: 6 Jul 2021

New research from the Tasmanian Institute of Agriculture (TIA) has revealed key insights into the grazing habits of dairy cows and the changes farmers can make to improve their bottom line.

Using high-tech sensor collars, TIA researchers have been watching every move a cow makes.

Led by TIA Research Fellow Mr Pieter Raedts, data is being analysed from a project that monitored 180 dairy cows within the herd at TIA’s Elliott Dairy Research Facility, being fed two different levels of a grain-based concentrate throughout an entire lactation period.

This is the first time that researchers have tracked the grazing behaviour of dairy cows with sensors over such a long period of time.

Over the entire 10 months, half of the cows received two kilograms of dry matter grain concentrates each day and the other half received six kilograms of dry matter per day.

Mr Raedts said they wanted to specifically look at the impact that a high grain diet had on cows’ behaviour while grazing pasture.

The team used MooMonitor+ sensors to measure the time the cows spent grazing, ruminating, and resting. They also subdivided the cows into groups according to breed (Crossbreed vs Friesian), body weight, and milk yield at the start of lactation.

“Dairy farmers generally try to get cows to graze as much grass in the paddock as possible, but feeding some grain, usually during milking, is very common,” Mr Raedts said.

“Over the last decade the amount of grain feeding in the dairy industry in Tasmania has roughly doubled, from around 600-700 kilograms per cow per year to between 1200-1500 kilograms.

“Most farmers, when feeding more grain, measure profitability based on the extra milk produced from the extra grain fed.

“We wanted to give farmers more information about what impact it has on the amount of pasture grazed, and how they might manage this to make sure this is not compromising the amount of pasture utilised, as this is usually the cheapest source of feed available.”

The team found that the cows receiving the higher level of grain produced more milk, as expected, but did not graze as much grass in the paddock.

The sensors showed a clear difference in the grazing time between the two groups, with the cows receiving the higher level of grain spending 13 per cent less time grazing each day.

“This means farmers who are looking to move to a high grain input system need to have a plan for utilising uneaten pasture because they will have a surplus,” Mr Raedts said.

“If this is not managed properly it is likely to be wasted. They may need to increase their stocking rate, plan for making more silage, or look at other ways to use the excess pasture.”

Mr Raedts said that the results showed how complex the dairy system can be.

“Dairy farming is like a spider web, make one change to one thread, and everything moves a bit,” he said.

“On top of the overall reduction in pasture grazed in response to the increased amount of grain fed, we also found that the season and breed of cow were important to consider.

“There were large differences between the different groups of cows, especially in early Spring, and between Friesian cows or Crossbreed cows.

“Initial findings of this trial have shown us that how cows respond to extra grain depends on several factors.

“These findings can help dairy farmers make better-informed, more profitable decisions, when looking to change the level of grains being fed.”

The team are now analysing the results further to determine the significance of the findings.

More information will be made available to Tasmanian dairy farmers when the results are published.

This research is funded by Dairy Australia.

TIA is a joint venture between the University of Tasmania and the Tasmanian Government.