Editor's note: This Practice Builder was contributed by Dennis Buckmaster, associate professor agricultural & biological engineering at Purdue University.
Total mixed rations are the feeding method of choice for the majority of dairy operations across the U.S. There are many configurations of equipment, layouts and protocols which can accomplish TMR delivery. But how do you know if the TMR is adequately blended? And, if the TMR blending is not adequate, how can you improve it?
To get the most performance out of a TMR, it is imperative to measure, mix test and monitor rations frequently. Closing the loop on feed delivery to measure the actual output and make changes will take more time, but it is the only way to be sure things are done correctly — regardless of who does the work.
There are a number of reasons that the delivered ration may be different than the intended ration. To close the loop in TMR delivery systems, the quality of the delivered TMR should be monitored. This could be done using physically or chemically observable tracers or simply particle size distribution. The tracer concept is also useful for evaluating within-batch variation.
While experiments involving laboratory analysis of large numbers of samples can be expensive and require statistical analysis, there is room for simpler "take some data and make a decision" type experiments on the farm.
Here are some suggestions for on-farm mixer experiments that may be 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 three 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 all the 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 excessive size reduction is occurring during mixing, fill the mixer 70 percent full with 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 forage and of the "blended" forage. 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; do not 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 a tracer added in "a corner" or particular spot in the mixer. Tracers such as a bucket of corn cobs, whole shelled corn, whole cotton seeds, miniature carrots, marshmallows or other easily physically identifiable/countable items may help assess mix uniformity. Be careful to choose tracers which will not be hazardous to animals which may consume the feed and tracers that are added in controlled quantities. If the tracer is weighed or counted, be sure that all samples are the same size or that the tracer concentration is normalized to sample size (e.g. kernels per 3 pound samples, not kernels per samples if samples vary from 1 to 3 pounds).
These simple experiments can help you understand how the mixer is working, if the TMR is adequately getting blended and where adjustments may need to be made.
It's also important for dairies to stay on top of mixer maintenance and repair; worn components can affect blend uniformity and size reduction. Scale errors immediately affect the delivered ration, so frequent calibration is also critical.