Ellinbank Research farm

By Dr Martin Auldist

Developing the ability to measure dry matter intake in grazing cows in near-real time is a major goal of the Smart Feeding project within the DairyFeedbase research program.

“Measuring pasture intake in individual cows has been problematic for farmers and researchers alike for decades,” says project leader and Agriculture Victoria researcher Dr Martin Auldist. “We can do it using synthetic markers of various kinds, including alkanes, but these techniques are labour intensive, time consuming and not practical for making day-to-day decisions on farms and during experiments.

“Knowing how much cows are eating in the paddock would be extremely useful,” says Martin.

“For example, knowing what nutrients cows are getting from pasture would allow farmers to formulate the supplement side of the diet more effectively. It would also allow farmers to identify cows that are more efficient at converting grass into milk.

“We do know that there is massive variation across the herd when it comes to pasture intake. Previous experiments at Ellinbank have shown that some cows eat at least 100 per cent more pasture than others.”

As part of the Smart Feeding project Martin, along with Agriculture Victoria researchers Dr Pablo Alvarez-Hess and Meaghan Douglas, is conducting a series of experiments aimed at testing whether on-cow jaw movement sensors could be used to help measure pasture intake. These sensors are sophisticated enough to distinguish between harvesting bites, chewing bites and rumination, and the data is available within 24 hours.

Image: Agriculture Victoria researchers Dr Pablo Alvarez-Hess and Dr Meaghan Douglas

Other researchers have attempted to approximate intake using time spent grazing and number of bites per day; however, this approach doesn’t account for variation in bite size.

“That’s the focus of these experiments,” says Martin. “We want to understand the variation in bite size and the main contributing factors.

“Eventually we want to come up with a predictive equation for bite size that incorporates plant factors such as pasture mass and allowance, and cow factors such as milk yield, liveweight, muzzle width and anything else that might be having an influence. Then we can use that bite size prediction along with number of bites to calculate pasture intake.”

The first experiment started in early June and will calculate bite size by measuring pasture disappearance for cows grazing in individual pasture plots. Twenty-four cows will be used, grazing pastures of different mass and allowance.

“This is our first attempt to estimate individual bite mass in grazing cows – it’s not an easy thing to do!” says Martin. “Hopefully the results will provide an initial understanding of the factors we need to measure to predict pasture intake accurately.”