A flexible approach to robotic milking in pasture-based systems could offer dairy businesses opportunities to improve labour efficiency, reduce the need for on-call staff and improve energy efficiency at certain times of the year.
FutureDairy project leader, Associate Professor Kendra Kerrisk, said results from a preliminary study indicated experienced cows could be transitioned from voluntary milking to semi-batch milking and back to voluntary without a negative impact on milking frequency or milk yield.
"A semi-batch milking approach at certain times of the year would appeal to some farmers with automatic milking systems (AMS), particularly those with seasonal or split calving systems," she said.
"In the past, we've tended to think AMS farms should be operated with either voluntary or batch milking and that swapping between the two would be difficult."
With voluntary milking, cows move around the farm by themselves: from the paddock to the dairy and on to the next feed allocation. The aim is to achieve a relatively steady flow of cows being milked throughout the day and night to maximise the utilisation of the robots.
With semi-batch milking, cows are generally held in a paddock and the gate opened at specific times for cows to move to the feedpad and then the dairy for designated milking sessions by the robots.
"Voluntary cow movement presents some challenges with seasonal or split-calving herds because there are times of the year when the number of cows per robot is relatively low," she said.
The challenges include difficulty maintaining voluntary cow flow (and the need to fetch more cows), reduced labour efficiency, higher power consumption per litre of milk harvested, managing small pasture allocations and the potential for milk quality issues in warm weather due to intermittent fresh milk flushing through the plant.
Some of these challenges can be addressed by deactivating some of the AMS box units or bails in the case of the automatic milking rotary (AMR). An alternative is operating with voluntary cow movement for most of the year, and switching to semi-batch milking in the months that the milking herd is significantly reduced. Semi-batch milking has the added advantage of avoiding the need for on-call staff during the night hours.
"Our concern was that the cows may struggle to shift from semi-batch milking back into voluntary movement when the herd size increased again," Assoc Prof Kerrisk said.
"We know from previous research that cows require a training and adjustment period when they are first introduced to an AMS with voluntary cow movement. We didn't know whether or not AMS-trained cows would be able to switch between semi-batch and voluntary movement."
In 2015 and 2016, the AMS at Gala Farm, run by Nick Dornauf and his partner Rebekah Tyler, in northern Tasmania operated with semi-batch milking for about eight weeks. With a split-calving system, there is typically a period of low milking numbers in the winter months when the milking herd drops down to 200 cows (from 600 cows at peak).
The software that runs the AMS collects detailed records on individual cows, allowing the FutureDairy PhD student Juan Molfino to analyse the impact of semi-batch milking at Gala Farm in 2016. In particular, he compared milking frequency, milk yields and concentrate consumption ù before, during and after the semi-batch milking period.
Mr Molfino said that results showed the effects of semi-batch milking on milking frequency were temporary with the cows smoothly adjusting back to voluntary milking (see Table 1).
"We created a model using the Gala herd data to analyse what happened to milk production," Mr Molfino said. "During the period of semi-batch milking, milking frequency and milk yield dropped slightly, which was to be expected as their access to the dairy was restricted during the weeks of semi-batch milking."
Mr Molfino said he was surprised when the herd reverted from semi-batch milking to voluntary that milking frequency and milk yield not only recovered but exceeded the levels in the original voluntary milking period.
"Our analysis accounted for stage of lactation and excluded freshly calved cows so the change in milking frequency and yield may have been associated with the spring flush in pasture quality and quantity," he said.
The increase in concentrate consumption (from 8.39 kilograms/cow/day to 8.61kg/cow/day during semi-batch milking) was also unexpected.
"It's possible the semi-batch milking resulted in cows accessing the feed stations in a more hierarchical order, which may have reduced the likelihood of more dominating cows preventing access to concentrate by less dominant cows," he said.
When the herd went back to voluntary movement, concentrate consumption dropped to 8.52 kg/cow/day, which was slightly higher than before the switch to semi-batch.
Although it was only a preliminary study, the results have given the FutureDairy team confidence that semi-batch milking for certain times of the year is a feasible management option for AMS pasture-based farms. And the benefits at Gala Farm were positive enough for semi-batch milking to become routine practice every year from mid-June to mid-August.
Gala Farm pioneers The semi-batch milking approach has been pioneered at Gala Farm in Tasmania where the Dornauf family milk up to 600 cows in a DeLaval Automatic Milking Rotary (AMR). Although calving is split between autumn and spring, the herd size drops back to about 200 in the winter months.
Nick Dornauf said 2017 would be the third year the herd would be semi-batch milked between mid-June and mid-August.
"It works really well for us," he said. "The main reason we tried it was to overcome poor voluntary cow movement at a time when the cows receive most of their feed at the dairy ù either concentrates or hay/silage at the feedpad. But there are many other benefits, including less pugging damage because the cows spend less time in the paddock and more time at the feedpad, a drop in power consumption and a better match with staff availability."
The semi-batch system at Gala involves the automatic gates opening 2.5 hours before the start of each milking session.
"The cows walk to the dairy at their own pace and have access to the feedpad before milking," Mr Dornauf said.
Unlike box AMS units, the AMR can be used with human cup attachment. "At this time of the year with fewer cows it's faster to turn off the robots and attach the cups ourselves," he said. "Most staff are on leave and there's minimal other work to be done on the farm so it's actually more convenient to milk twice a day.
"Milking in two, concentrated sessions a day means the dairy isn't running 24/7 for these months. This gives staff a break from being on call at night and on weekends.
"Another bonus is our power bill drops by 40 per cent during these months. And it creates a really good opportunity for scheduled maintenance by our local dealer or for us to train heifers. The rest of the year, when the robots are running 24/7 it's awkward to have downtime for maintenance and heifer training."
But the big question is how well do the cows cope with going back to voluntary milking when the milking numbers increase with spring calvers?
"We were a bit concerned about that before we tried semi-batch milking," he said. "But it turned out to be a non-issue. In fact, the cows tell me when it's time to revert to voluntary cow movement. We see signs in the cow behaviour that they want to return to the dairy sooner than we are scheduling. It's a combination of increased pasture in the diet and the number of fresh cows."
Contact: FutureDairy, Associate Professor Kendra Kerrisk, phone 0428 101 372, email email@example.com.
FutureDairy's major sponsors are Dairy Australia, DeLaval and the University of Sydney.
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