Kammel et al. (1995) suggested that mixer design and dairy feeding are both an art
rather than a science. As time passes, hopefully this is becoming less true, but there is
some truth to this. Because there are some gray areas and less black and white than
most of us would like, there may be a need for some on-the-farm experimenting with the
TMR mixer. Buckmaster and Muller (1992) compared two mixer types and worked
through the statistical analysis required; they used particle size distribution and
chemical attributes to track uniformity. Experimentation may bring to mind sophisticated
statistical data analysis, expensive replication, and tremendous resource commitments.
While these cannot be ruled out or considered unnecessary, there is room for simple,
“take a look and make a decision” type experiments on the farm. Here are some
suggestions worth trying.
Consider experimenting with mixing protocol. Depending upon the type of mixer and
the material flow in the mixer, location of the placement of ingredients into the mixer or
the sequence of loading can affect mix uniformity and resulting particle size distribution.
By changing one thing at a time, and with just some simple replication (do the same
thing at least 3 times), you may be able to observe some meaningful differences in
outcome. If the mixer is generally run when ingredients are put in, try leaving it off until
the all ingredients are in. If you usually run the mixer for 10 minutes or 150 rotations of
some drive sprocket, try cutting it in half and see if anything changes.
If you suspect significant particle size reduction during mixing, fill the mixer 70% full of
only a single forage. Run the mixer as though it were a complete ration for the length of
time a ration is typically blended. Measure the particle size distribution of the original
silage and of the “blended” silage. You may need to seek advice and counsel from
someone knowledgeable about basic statistics, but most anyone can spot trends or
large differences. Replication is important, so don’t rely on results from just one test.
A variation on the single forage mixing test to evaluate particle size reduction is a single
forage ration with water added in “a corner” or particular spot in the mixer. An on-farm
analysis of moisture content of several samples taken from the unloading chute (with
perhaps varying mixing times) could give an indication of mix uniformity. As mentioned
above, tracers (such as a bucket of corn cobs, whole shelled corn, whole cotton seeds)
or other easily physically identifiable/countable items may also be a help in assessing
mix uniformity. Be careful, though, to choose tracers which will not be hazardous to
animals which may consume the feed and tracers that are added in controlled quantity.
If the tracer is weighed or counted, be sure the samples are consistent in size or that
the tracer concentration is normalized.