By July in Quebec, the silage clamp is getting warm, the third cut is coming off the field, and corn silage prep is on everyone’s mind. It is also the time of year when bunk refusal shows up before noon and a ration that looked fine in February starts separating into long-stem fibre on top and fines underneath. The cows sort. Intakes drop. Production follows.
The instinct is to blame the bunk. It is rarely the bunk.
In cold weather, a slightly over-processed or under-blended batch often gets away with it. Frozen forage clumps together. Steam and moisture slow particle migration. The ration lands, stays put, and the cows clean it up before anything separates. Heat removes all of that forgiveness. A batch that tmr sorts bunk-side by midmorning in July would have been eaten clean in January. The fault was there all winter. You just could not see it.
Fill Order and Mix Time: Where Separation Starts
Most bunk sorting traces back to two decisions made before the first ingredient ever hits the tub.
Loading long-stem dry hay early in a twin-auger machine and then running the auger for the full blend time is the most common error in summer feeding. The hay processes for longer than it should, and by the time concentrates and silage go in, the fibre fraction is already cut shorter than the ration was designed for. Short fibre does not bind the mix together. When the batch hits the bunk at 28°C (82°F) and the cows start sorting with their noses, the fines migrate down and the effective fibre fraction rises to the surface. Refusal follows quickly because that top layer carries low palatability and almost no energy density.
The correct sequence for a twin-auger vertical machine is silage and wet ingredients first, concentrates and minerals partway through, dry hay last. Hay added late gets cut by knives that are already working against a dense, moist mass. Processing is faster and more uniform. Blend time after the final ingredient drops to the minimum needed for homogeneity, not whatever the operator used to run in winter when extra time seemed harmless.
Over-mixing is not a minor issue. Four or five extra minutes of auger time after the correct texture is achieved will grind particle size down enough to reduce effective fibre function even if the Penn State separator screen data looks acceptable. In summer, that difference shows up at the bunk within two hours of feeding.
What Decagonal Walls and Kicker Action Are Supposed to Do With Long Fibre
A round-walled tub lets a round bale spin with the auger. The bale follows the rotation, never catching, and processing time drags out. The flat sides of a decagonal tub interrupt that spin. Material catches against the angles, pressure builds at the corners, and the knives engage the fibre earlier in the cycle before the full load weight is in the tub. The practical result is that you can process the same bale in less time, which reduces the risk of over-running the mix once concentrates are added.
The geometry also matters for auger-to-wall clearance. Triangular gussets at each corner of a decagonal tub eliminate the gap that opens up in a round tub where the auger flight cannot reach. Material that pools in dead corners does not blend. It sits there, dry, and discharges into the batch as an unmixed pocket. In warm weather those pockets show up as visible fibre clumps in the bunk. For a more detailed look at how clearance drift affects mix quality over the life of a machine, the piece on auger-to-wall spacing and mix quality covers the mechanics and the field checks worth doing regularly.
The kicker plate is the other variable most operators underestimate. Its job is to sweep feed off the tub floor and redirect it onto the base of the auger flight, where it gets lifted and tumbled back into the mass. A worn or undersized kicker leaves a dry ring of material on the floor that never fully integrates. In summer, that dry ring is always fibre. It ends up on top of the bunk delivery as a loose, unblended layer. Kicker condition deserves its own inspection interval. The kicker’s effect on mix quality is significant enough that a plate in poor condition can undo a correctly loaded batch entirely.
A Short Diagnosis Path From Bunk Refusal Back to the Tub
Start at the bunk, but do not stay there long. If cows are sorting long fibre to the top and leaving it, walk back through the following in order.
- Discharge door setting. An incorrectly adjusted door deposits material unevenly along the bunk. One section gets a high proportion of fines, another gets fibre. The cows at the fibre-heavy section sort aggressively. The fix may be at the door before anything else. Door calibration on a VT machine affects bunk line consistency more than most operators expect, and the correct setting changes with batch weight and tub fill height. Checking the discharge door setting for even bunk lines is a five-minute job that eliminates a common source of apparent sorting.
- Knife condition. Dull knives on the auger do not cut fibre, they fold it. Folded fibre looks processed but behaves like long stem in the bunk. Check edge condition across all positions. Tungsten-carbide coated replaceable knife edges hold their geometry longer than bare steel, but they still wear. The outer edge goes first. If you are replacing whole knives when only the outer section is gone, you are spending more than you need to.
- Load sequence and timing. Pull the batch log from the scale system and confirm the actual sequence versus what was intended. Scale logs on machines with programmable recipe systems show you exactly when each ingredient was added and at what cumulative weight. A feeder who added hay early and ran an extra three minutes of mix time after the concentrates will show it in the log. Correct it in the recipe, not in the field by guessing.
- Kicker plate geometry. Get in the tub after a clean-out and check how much clearance the kicker has to the floor. Any visible ring of compacted or smeared material around the tub base is evidence the kicker is not doing its job. LEO Agriculture’s VT Series specifies a replaceable kicker as a standard feature precisely because this component has the largest single impact on feed flow and mix homogeneity in the lower third of the tub.
Summer Is When the Margin Disappears
Heat stress and sorting hit simultaneously in a Quebec July. Cows that are already managing thermal load cannot afford to spend energy selecting a ration that should have been homogeneous when it left the mixer. The mix problems were likely there in March. Summer just removes the buffer that cold weather provides.
The good news is that every failure point listed above is diagnosable in a morning and correctable within a day or two. You do not need a new machine. You need the right load order, a kicker plate that is doing its job, knives that still cut, and a door setting matched to your delivery method. Get those four right and the bunk looks after itself.
