Spring in northern Victoria has a way of turning a tidy feeding system into a logistical headache almost overnight. Herd numbers climb, grass growth is unpredictable, and bunk lines that ran fine through winter suddenly stretch across three separate paddocks or yards. The mixer that handled everything through July starts spending half its morning travelling instead of mixing. That is when the question about delivery wagon volume stops being theoretical.
The common mistake is sizing a delivery wagon against the mixer tub. A 12 m³ mixer does not automatically want a 12 m³ wagon. The two jobs are different. The mixer’s volume tells you how much feed you can blend in one pass. The wagon’s volume needs to match how much feed you can actually move and discharge across your drop points before sorting becomes a problem and before the mixer sits idle waiting for the wagon to return.
Size from Tonnes and Drop Points, Not Tub Volume
Start with daily TMR tonnage and work backwards. If you are feeding six tonnes of mixed ration per day across four bunk locations, you need to know how many wagon trips those four drops require, and whether your mixer can run its next batch while the wagon is still on its first run.
The logic runs like this. A mixer with a genuine hourly throughput of two batches per hour needs a wagon that can clear its load and return before the second batch is ready. If the wagon is too small, it makes extra trips and the mixer waits. If it is too large, you are dragging weight and width through lanes that were not built for it, and you risk a partially loaded wagon on the shorter runs, which is where segregation starts.
A rough working rule: calculate your largest single drop point load, add a reasonable buffer for the transit fill between that drop and the next, and size your wagon to cover two or three consecutive drops before it needs to return. For most northern Victorian dairies running a mid-size vertical mixer, that puts the practical wagon range somewhere between half and three-quarters of the mixer’s batch volume, depending on how many animals are at each stand. If your ration is dense, dry matter content above 50%, that wagon fills heavier for a given cubic capacity, so review what the running weight does to your lanes and your tractor drawbar.
Operators managing separate groups, fresh cows, mid-lactation, dry cows, on different sides of the shed sometimes find it easier to think in terms of group ration weight per visit rather than total daily tonnes. Each group is effectively its own drop-point sequence. Size the wagon to handle your largest group ration in a single load if you can. Splitting a group ration between two wagon loads invites inconsistency at the bunk, particularly if there is any delay between the first and second delivery.
Yard and Lane Limits Around the Silage Face
The argument for keeping the main mixer close to the silage face is straightforward. Every metre you drive a loaded, heavy mixing unit through a yard is wear on the tractor, compaction on the concrete or soil, and time that is not mixing. Spring flush conditions make this worse. Soft ground opens up around September in the Riverina and northern Victoria, and a fully loaded mixer wagon tracking through a paddock laneway every morning does not improve things.
A delivery wagon’s narrower profile and lighter unladen weight mean it can move through areas that would punish a full mixing unit. It also tends to sit lower to the ground when loaded, which matters in sheds with restricted clearance. Some operations find the real payoff is not the extra capacity at all, but the ability to keep the mixer parked alongside the stack and let the wagon do the kilometres.
Lane width is a practical ceiling. If your internal laneways run less than four metres clear, a large custom delivery box becomes a problem regardless of how well it is built. The 25 Series delivery wagons in the LEO Agriculture lineup, the 2512, 2516, and 2520, are built specifically for this kind of farm-circuit work, with low loading heights and discharge systems meant for the tight turns that larger units cannot manage. The custom boxes in the 28 to 40 m³ range suit trailer or truck mounting and are aimed at high-volume operations where laneways can support the footprint.
Before you commit to a wagon size, walk the full circuit. Measure your tightest corner, note where the grade changes, and check what your tractor can actually pull on a loaded return up an incline. Those numbers matter more than any catalogue figure.
Keeping the Ration Intact on the Way to the Bunk
A well-mixed TMR can sort badly over a few hundred metres of gravel laneway. Long fibre migrates to the top and fines settle. What lands in the bunk looks different at each end of the run, and cows are not forgiving about it. This is not a mixer problem. Ration quality frequently gets lost in transit, not at the mixing stage.
Wagon geometry plays a role here. A taller, narrower hopper body tends to hold the ration column together better than a wide shallow one, because there is less lateral surface for material to roll across during cornering. Floor conveyors and discharge speed both affect how evenly the ration lands at the bunk. A fast, uncontrolled discharge can throw light material forward and leave dense particles behind, which recreates the sorting problem at the point of delivery.
Discharge door adjustment is worth understanding in detail before you buy. Getting the discharge door set correctly for even bunk lines is something operators often underestimate until they start watching individual cows pick through a feed face that is not consistent from one end to the other.
A partially filled wagon is the other common culprit. A delivery wagon running at 40% capacity has far more internal air space for material to move around in during transit. Where possible, load each run to at least 70% of the wagon’s volume. If your group sizes do not allow this, you are probably looking at a wagon that is too large for those groups, or a scheduling change that combines groups on a single delivery circuit.
Some operations add a kicker to manage ration placement and spread. Matching the right kicker to the ration type is its own topic, but it is worth factoring into your delivery wagon specification if your ration runs high in long-stem hay or silage. The interaction between the wagon’s discharge speed and the ration’s physical characteristics determines what actually lands in front of the animals. Understanding how bolt-on kicker sizing works with different ration types can save a lot of adjustment time once the wagon is in service.
Throughput and Timing
Matching delivery wagon volume to mixer output is ultimately a scheduling exercise. Map out the full morning run: when the mixer starts loading, how long a batch takes, when the first wagon load can leave, how long the circuit takes, and when the wagon returns for its second load. Then check whether the mixer has had to wait at any point in that sequence.
If the mixer consistently waits on the wagon, the wagon is too small or the circuit is too long for one unit. If the wagon consistently waits on the mixer, you may be oversized or your mixer throughput has a bottleneck. Neither is ideal, but an idle mixer is generally the more expensive problem. It is worth running the timing exercise on your peak spring feeding day, not an average day, because that is when the mismatch will show up.
For larger operations where peak spring loads push beyond what a single wagon can handle efficiently, a second smaller wagon running a separate circuit is often more practical than stepping up to a single unit that is too large for the tighter areas of the farm. The capital cost is similar. The operational flexibility is better.
