You open the door, start unloading, and the first half of the bunk looks great. Then a clump of minerals or a slab of unprocessed hay comes out. That’s a dead spot, and it means some animals got a different ration than others.
What a dead spot is
In a vertical mixer, feed should roll up the auger and down the walls continuously. A dead spot is anywhere feed isn’t moving, usually in corners, at the top, or near the door. Ingredients sitting there don’t get mixed.
Common causes and fixes
Overloading. Fill a vertical too full and the top layer can’t roll. Leave headroom.
Underloading. Too little feed, especially in a twin auger tub, and the augers can’t build that rolling motion. Size the load to the machine, or the machine to the load.
Wrong load order. Hay on top of silage floats. Minerals dumped last sit on top. Fix the order: long forage first, liquids last, small ingredients in the middle.
Restrictors set wrong. Restrictors in too far for too long can make material bridge. Pull them back after processing.
Worn knives or flighting. A worn auger lifts less and cuts less. Check the auger edge and knives.
Wet, sticky rations. Very wet feed or too much liquid early can clump and stick to walls. Add liquids last and evenly.
Too short a mix time. Sometimes it’s simply not finished. Mix a bit longer after the last ingredient and test.
How to find them
- Sample the bunk at the start, middle and end of each unload and compare.
- Run a particle separator test on each sample.
- Look in the tub after unloading for buildup on walls and corners.
Testing for uniformity
A simple way to check mix uniformity is to take samples along the bunk and compare them. Look at particle size, but also at visible ingredients. Can you see grain or mineral more in one place? If you have access to a lab, some farms test samples for a marker nutrient to check uniformity.
Twin auger considerations
In twin auger tubs, dead spots can form between the augers or at the ends if the load is uneven. Load across both augers and keep load size above the minimum.
Door and discharge area
Feed can sit near the door if the door seal or shape lets it collect. Check this area after unloading.
Liquid addition
Adding liquids too early or in one spot can create wet clumps that stick to walls. Add liquids last and spread them across the tub.
Mix time and auger speed
Running the auger too slow may not move feed well. Follow the recommended PTO speed. Mix long enough after the last ingredient, but don’t overdo it.
Machine wear
Worn flighting edges lift less feed. A worn floor near the auger can change how feed moves. If the machine has years of use and mixing has gotten worse, inspect the auger and floor.
When to call the dealer
If you’ve checked load size, order, knives, restrictors, liquids and time and still have pockets, call your dealer. They can check auger condition and setup.
A simple uniformity check anyone can do
Next time you unload, stop the mixer at the start, middle and end of the bunk. Grab a handful of feed at each spot. Lay them side by side on a board. Look at the colour, the amount of grain, the length of the forage. If they look different, the mix isn’t even. It’s not a lab test, but it’s quick, it’s free and it catches problems early.
Do it after any change in ration, load size or operator.
Quick questions
Can an overfilled tub cause dead spots? Yes. Feed at the top can ride around without rolling down to the auger.
Do worn knives cause pockets? They can slow processing, leaving clumps of long forage.
Is a quick hand check enough? It catches big problems. Use a particle separator for the full picture.
How often should I check? After any ration or operator change, and every few weeks otherwise.
When it’s the machine
Some tub shapes and auger designs move feed better than others. If you’ve fixed load size, order, knives and time and still see pockets, talk to your dealer about the auger and tub condition.
Our VT twin auger and heavy-duty mixers are designed to keep feed moving through the whole tub, but no machine fixes a bad load habit.
Bottom line? Uneven mix means uneven cows. Sample it and fix it.
Learn more about LEO Agriculture and our full line of feed mixers and manure spreaders.
