AT long last, in June, Agriculture Victoria researchers finally had enough pasture on the Ellinbank research farm to complete what was supposed to be an autumn experiment.
An experiment using 40 cows was conducted as part of the Smart Feeding theme within the new Dairy Feedbase program.
The experiment was led by Dr Marlie Wright and had two main aims: the first was to measure the effect of time away from pasture on grazing behaviour and dry matter intake.
The second was to measure the change in the availability and quality of pasture as grazing progressed, to understand the differences in the feed available to the first and last cows back to the paddock.
The 40 cows were allocated into five treatment groups of eight cows each.
Groups were then released back to their paddock sequentially.
One group was walked straight to the paddock while others were sent back at 45 minute intervals over three hours, thus mimicking what occurs on farms with large herds or small dairies.
Cows were released in the same order after every milking, again mimicking what happens on a commercial farm.
Some cows, therefore, were away from the paddock for six hours per day plus walking and milking time.
The experiment lasted 15 days.
To measure grazing behaviour, cows were fitted with jaw movement recorders and activity monitors that allowed Marlie to record the time cows spent grazing each day, the total number of bites the cows took each day, and the rate at which cows grazed (bites per minute).
In addition, the n-alkane technique was used to measure the total daily dry matter intake of cows.
This involved orally dosing the cows with a small amount of synthetic wax twice per day for 12 days and then measuring the concentrations of synthetic and natural waxes in the faeces for the final six days.
A complex mathematical equation then allows calculation of daily dry matter intake.
At the same time, detailed measurements were made of pasture mass and quality prior to grazing, and then immediately prior to each group of cows entering the paddock.
This was mostly done using a rising plate meter to estimate pasture mass and by taking pasture samples across the paddock for analysis of nutritive characteristics.
Measurements of pasture mass were also made by flying over the paddocks with an unmanned aerial vehicle.
Overall, this information will allow Marlie to assess the variation in intake and therefore milk yield that occurs when there are delays in cows getting back to the paddock.
Preliminary results showed that the last cows back to the paddock spent almost twice as long grazing, presumably because they had to work harder to find the same amount of grass.
This correlates with the observation that the last cows walked further around the paddock than the first cows, and spent less time lying down.
Meanwhile, in the paddock, around 30 per cent of pasture dry matter had disappeared by the time the last cows got there.
I’ll provide a more complete summary of the results when they come to hand but almost certainly there will be the potential for a more equitable allocation of farm feed resources across the herd.
Watch this space.