Many dairy farmers have identified that the first cows into the dairy produce more milk than the last cows so now Dr Martin Auldist and his team - as part of the DairyFeedbase 'Smart Feeding' project based at Agriculture Victoria's Ellinbank research farm - are working on developing farm management systems to increase the herd's milk yield by neutralising these differences and increasing the average milk yield response per kilogram of feed.
The Smart Feeding project has found that the first cows in the milking order and therefore the first ones back in the paddock produce up to 5kg more milk than the last cows.
The team - including research scientists Dr Marlie Wright, Meaghan Douglas and Dr Pablo Alvarez - have been working on comparing milking order, individual cow dry matter intake and milk yield to identify feeding strategies to overcome these differences.
"Farmers have long known about the milk yield difference, but the cause hasn't been clear," Dr Auldist said.
"The many theories included that the lead cows want to be milked because they are higher yielders and have greater udder pressure, that the higher-yielding cows are hungrier and want to get to the grain, that there are dominance issues driving milking order, and that the last cows are sick, lame or older and therefore lower yielding.
"Our research has shown that the difference is mainly correlated with the amount of time they are away from the paddock and therefore feed."
The project team used on-cow jaw movement recorders to monitor grazing behaviour and found that the last cows back to the paddock modified their grazing habits to compensate for being late back.
While they might spend up to nine hours per day away from the pasture, they actually spend more time eating trying to catch up.
"It's not that they don't have time to eat, it's more about the fact that they're not getting a fair go in the paddock," says Dr Auldist.
"By the time the last cows get back to the paddock, nearly 40 per cent of the pasture dry matter is gone.
"As well as that all the good stuff is gone because grazing animals tend to select the pasture with the highest energy and protein first and leave the part that is higher in fibre."
The next step in their project is to test some mitigation strategies.
In the coming months, the team will focus on splitting paddocks up and experiment with different ways of reserving some for the cows that get back to the paddock later (including virtual fencing, smaller herds and smaller paddocks).
They will also assess different supplement strategies that may help even up dry matter intake across the herd.
Some considerations for the team for those strategies is how labour intensive the process is; how much infrastructure is required; and how technology can assist in these strategies.
Part of the project scope is to trial the mitigation strategies selected and then assess them according to return on investment.
The key question that Dr Auldist and his team are looking to answer is whether implementing different feed strategies will increase the whole herd milk yield rather than just equalising the yield from each cow.
DairyFeedbase co-director and Dairy Australia director of major innovation projects Kevin Argyle said: "The work that the Smart Feeding project has done on identifying and confirming the 5kg yield difference is fantastic, and with Dr Auldist and his team looking to show a herd yield increase with different feeding strategies, we are hopeful of an overall increase in the milk yield which could be in the order of $120 per cow per year."
DairyFeedbase is a joint venture between Dairy Australia, Agriculture Victoria and the Gardiner Foundation, and is the dairy industry's leading applied research and innovation program.