You and Your Mixer: Mixing Properly?

Mix Quality is Important!

Serious consideration must be given to determining the quality of the feed mixture provided to cattle, especially if medications or urea are to be used. Maintaining this mix quality ensures proper dosing, which is important to ensure effective treatment and to avoid toxicity in different pockets of the same batch. This applies to any producers using TMR (Total Mixed Rations), quasi-TMR or farm-mixed concentrates.

In February of 2000, the Canadian Food Inspection Agency (CFIA) proposed new regulations, under the authority of the Health of Animals Act - Regulations Respecting the Making of Medicated Feed, that would have required licensing and upgraded control measures for manufacturers of medicated animal feeds in Canada. Since that time, CFIA has consulted with stakeholders and carried out pilot projects in Ontario and Canada, and has replaced that earlier regulatory plan with on-farm audits under a different authority.

Regardless of the regulatory aspects, it is in the best interests of the cattle producer to ensure that TMR or volumetric mixing technology is being used properly. This will ensure equal nutrition and medication levels across the group of animals being fed. Proper mixing will produce a homogeneous mixture which maximizes the benefits associated with purchased feed additives and ingredients while minimizing the risks.

Indicators of Mixing Performance

There are a number of ways of testing a ration for proper mixing. All are estimates of whether the ration fed at individual sample points along the bunk is equivalent to the theoretical, or intended ration. The following are required to make this determination:

  • verification of equipment
    This includes the metering devices, scales, and mixers used. When purchasing new equipment, including TMR mixers, ask for mixing performance specifications on the models you are considering. Determine the accuracy of all scales by using a known test weight of material, appropriate for the size of the scale.
  • sequential feed analysis
    This estimates the amount of variation among samples of the mixed feed (coefficient of variation, or C.V.). Several samples are taken and then analyzed as follows.
    1. concentration of actual medicating ingredients in completed feed (expensive); OR
    2. use of tracers to estimate vitamin/mineral/medication or feed fraction mixing. These tracers can include added salt, starch from concentrate sources and trace minerals from the mineral package (low cost)

Speak to your nutritionist, feed provider, or laboratory service provider to determine if mixer verification is needed in your situation, and what method and package is most appropriate.

What is a medicating ingredient?

According to the CFIA, a "medicating ingredient":

  • includes ionophores and other common feed additives such as MGA
  • is a substance intended for use in the prevention or treatment of disease in livestock
  • a substance, other than a feed, intended to affect the structure or any function of the body of livestock, and that has an assigned drug identification number (DIN) under the Food and Drugs Act

What is acceptable mixing?

The CFIA had proposed the acceptable coefficient of variation (C.V.) for mixers to be set at:

  • 5% for premixes (e.g. commercial mineral premix)
  • 10% for supplements (e.g. commercial supplements)
  • 15% for complete feeds (e.g. TMR, on-farm concentrates)

Based on my experience, I would suggest that producers using proper mixing equipment including TMR mixers should easily be able to achieve 10% or better on-farm.

Protocol for Mixing Verification

The following is a protocol that I have used on-farm for TMR mixers, and I have found to be effective in giving excellent information to assess mixing times and the effectiveness of premix and medication inclusion throughout the ration. It can be adapted for volumetric mills as well.

  1. Prepare the (TMR) ration as normal. (Note the inclusion order and rates of feeds and their dry matter)
  2. Include salt at a level higher than normal for ease of analysis and to distinguish from back-ground mineral levels in the forages and mineral package. Successful levels used to date range from 1 to 4.5% of dry matter as sodium chloride, depending on the purpose.
  3. Allow final mix to proceed as normal.
  4. Dispense feed, taking 3-12 random samples by one of the flowing methods;
    • Pans placed randomly in the bunk, sampling feed as it is placed as shown in Figure 1.
    • Samples harvested as they leave the mixer, auger or conveyer outlet
    • note: sample should not be taken as a grab sample from the bunk or a pile after dispensing, as the 'randomness' will be questionable
  5. Submit for sodium analysis to be reported as one report, including the C.V. for the mixer (calculated by laboratory)
    • A similar protocol may be used to test for medications, trace minerals or starch.
  6. If the laboratory does not provide the C.V., you can do it yourself. The CV is calculated by taking the sample set and then performing the following calculation, which can be conveniently done in a spreadsheet program:
    C.V. % = [S.D / Mean] x 100
    Where 'S.D.' is standard deviation of the tracer concentration in the sample set and 'Mean' is the average tracer concentration in the sample set.

Figure 1. Pans placed in a bunk for sequential analysis of manganese to determine a mixer CV
Image of pans placed in bunk Image of pans collecting sample for analysis

So What?

Ensuring proper mixing is important to the farmer to maximize return on investment for medications, premixes and ingredients used in the ration, and to prevent toxicity from poorly mixed ingredients. Having simple and low-cost data such as this C.V. calculation allows mixing times and ingredient loading order to be evaluated. Also, having some baseline data may also be very helpful to demonstrate due diligence in the use of medicating ingredients, should you ever need to show it.

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