The most common sizing mistake in mixer procurement is buying for the herd you have right now. It feels responsible. It keeps the capital cost down. And it tends to cost more than any savings within a few years, once you are running the machine at its ceiling during a growth phase you saw coming from the start.
Sizing a vertical TMR mixer well means thinking about your largest likely batch first, then working backwards to confirm the machine fits where you are today.
The Number That Actually Matters
Rated capacity is not a target. It is a ceiling. Most mixers run most efficiently somewhere between sixty and seventy percent of their rated volume at the low end, up toward full capacity at the high end. Drop too far below that lower threshold and you start losing mix consistency. The material does not move the way the auger geometry was designed to move it. Mix times stretch out. What ends up in the bunk is not the uniform ration your formulation called for.
This is why batch efficiency matters as much as raw capacity. A machine that is too large for your current batches will underperform on those batches every day, even if it has plenty of room to grow into. A machine that is too small hits its ceiling and stays there.
Neither is a good outcome. The goal is a machine sized so your current batches fall comfortably within its efficient working range, with enough headroom above that to absorb herd growth without forcing a premature replacement.
Vertical TMR Mixer Options Across the Range
LEO Agriculture builds its vertical feed mixer lineup in two series. The VT Series runs from 6 to 21 cubic metres, covering dairy, beef, and sheep operations of varying scale. The HD Series picks up from 16 cubic metres and runs to 45 cubic metres, built for large-scale dairy, beef, and feedlot operations, with truck-mount capability for those running mobile feeding programs.
That range matters because it gives operators a genuine continuum to plan against. There is no awkward jump where you outgrow one category and land in a much larger machine than you need. The overlap between the two series in the mid-range is deliberate.
For smaller operations or those managing multiple smaller mobs separately, the Mini Mixer range offers a compact footprint with full vertical mixing capability, which keeps options open without committing to a larger tractor requirement before the herd justifies it.
What Goes Into the Sizing Calculation
Head count is the obvious input, but it is not the only one. Ration density varies significantly depending on what you are mixing. A high-silage ration behaves very differently from one heavy in dry hay. Feeding frequency changes how large each batch needs to be. And tractor horsepower sets a hard limit on how much machine you can actually run.
Get any one of these wrong and the volume figure you land on will be off. Underestimate ration density and you end up with a machine that cannot physically hold the weight of a full batch even when the volume looks right. Ignore feeding frequency and you might size a machine that works today but forces you into a second daily mix far sooner than you planned.
LEO Agriculture offers an online Vertical TMR Feed Mixer Size Calculator built to help operators work through these variables together and arrive at a recommended mixer size, rather than relying on a single head-count rule of thumb.
Building in Headroom Without Oversizing
There is a practical middle ground between buying for today and buying more machine than you can run well. It starts with projecting your herd size out a few years, not just from optimism but from your actual expansion plan. If you are planning to add animals in the next two or three seasons, that growth belongs in the sizing conversation now.
The question to ask is not what size fits my current batch, but what size keeps my current batch in the efficient working range while leaving room for the batches I will be running when this machine is five years old.
Tractor match is the other constraint that shapes this decision. A larger mixer requires more horsepower to run correctly, particularly when processing round bales or high-fibre rations. Stepping up in mixer volume without confirming your tractor can handle the load at full capacity is a common oversight, and it tends to surface at exactly the wrong time, during peak feeding periods when throughput matters most.
Auger Design and Its Effect on Sizing Decisions
Mixer geometry affects how much useful work a given volume can do. The LEO Diamond auger design uses a square cutting principle, with knife placement creating pressure zones that drive bales into the cutting area efficiently. Between twin augers, that pressure zone works from both sides at once, which shortens processing time and reduces the horsepower demand per tonne of feed mixed.
The bolt-on kicker system on the auger plays a direct role in batch efficiency. The kicker scrapes and sweeps material off the tub wall, lifts it up through the centre, and pulls it back into the auger. Without a functioning kicker, feed packs against the wall and flow collapses. Mix times increase. The ration loses uniformity. Kicker sizing is matched to ration type: larger for high-hay rations, smaller for wet rations, with an Extreme option for low-density materials.
Both of these design details affect how consistently a machine performs across its working range, which is directly relevant when you are relying on a mixer to deliver a uniform ration at the lower end of its efficient volume during the early years of a new machine’s life.
If you are planning a new build or an expansion and want to work through the capacity question properly before committing to a size, the TMR Size Calculator is a reasonable place to start.
