Luke Stock is a dairy farmer based near Gatton in South-East Queensland, milking 110 jersey cows in a pasture-based system. Prior to 2015, Luke ran a Partial Mixed Ration (PMR) system where maize silage was grown by a neighbour and bought-into the farm to feed the herd, alongside by-products such as brewers’ grain. In 2016. Luke moved to a pasture-based system with 3kg/day of grain fed to each cow in the dairy, and minimal silage is offered apart from brief periods in winter when its quite wet on the farm and grazing is difficult, and during autumn when the farm pasture base transitions from kikuyu to annual ryegrass.
Pasture composition is kikuyu dominant in the summer months, and every autumn an annual ryegrass is oversown into the kikuyu sward to provide decent quality feed in winter when the kikuyu is semi-dormant. Like most Queensland farms Luke has a year-round calving system, and the switch to a mainly pasture-based feedbase instead of a PMR was driven by several factors including the desire to reduce costs and the risk profile of the farm, as well as the soil type (the farm is located in the extremely fertile Lockyer Valley) with deep-clay topsoil.
“Our focus is around efficiency – this farm is a cash flow farm” Luke said. This means that it’s a low risk farming operation where there is a greater focus on cost control. Luke has observed a significant reduction in overhead costs on the farm since reverting to the pasture-based system.
The kikuyu sward was planted in 2016 after the switch away from the PMR system. However, management of the kikuyu sward according to the PUP grazing principles only started 20 months ago on Luke’s farm after seeing the research at Gatton carried out by the C4 milk team.
PUP is an acronym for ‘proportion of ungrazed pasture’ which describes the key principle behind the management technique. Essentially, PUP enhances the cows’ natural style of grazing; grazing across pastures horizontally in layers selectively consuming only leaf material (Figure 1). Cows naturally avoid grazing contaminated areas, and when permitted will also actively avoid grazing down into the stemmy strata of the sward, where traditional grazing methods would restrict grazing area to achieve target residuals and utilisation, and therefore potentially limit intake. Typically, in kikuyu swards, a residual height of 10cm is maintained when managing according to PUP grazing principles.
Figure 1 - Plant structure and grazing height for Kikuyu pastures observed during grazing trials at Gatton.
Luke has seen a significant improvement in milk yield and profitability on the farm since the adoption of the PUP grazing principles: ”we saw some really good benefits of PUP grazing, even within the first eight weeks of trying it, initially with an improved milk yield response. We go around the rotation a lot quicker that previously and don’t graze into the sward as much so the cows are eating leafier, better quality pasture. We also use heifers to follow the main herd and eat the stemmier residual, though we still aim not to go below a 10cm residual, in accordance with PUP grazing principles.” This practice ensures that the leaf component of the pasture recovers and grows much faster with bigger leaves, than if they were grazing the kikuyu to a residual of 5cm, as demonstrated by the C4milk research team at Gatton.
In winter months, the kikuyu slows a lot in winter and annual ryegrass is often oversown. In that instance, the residual is grazed tightly prior to sowing of the annual ryegrass seed and mulched to reduce the competition with the ryegrass during its establishment phase in the late autumn/winter months. Luke is really happy with the use of PUP grazing principles on the farm: “To me, PUP grazing just makes sense – why force your cows to chew that lower quality, stemmy strata layer of kikuyu between 5 and 10cm?”
Dave Barber, the leader of the C4 milk project at university of Queesland, said that they had worked closely with Luke pre-2016 to try get his Jersey herd to eat more PMR and really struggled to get a milk response, but the switch to PUP grazing management 18 months ago generated an increase in margin over feed costs of about 6 cents per litre. As growth in the tropical areas increase dramatically in the warmer months in the tropics, the quantity of feed grown per day increases dramatically to over 100 kg DM/day for extended periods, and so it’s actually quality of pasture that is the limiting factor in these regions as opposed to yield. Therefore, the PUP grazing management principles seem to work quite well for these tropical regions as cows end up consuming leafier, higher quality pasture that in turn generates greater milk yields.