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The Challenge of TMR Sampling
Total Mixed Rations (TMR) are designed
to:
- Provide balanced
nutrition in every bite.
- Prevent sorting
of individual ingredients.
- Allow the
utilization of less palatable feeds by blending and disguising
with larger amounts of palatable feeds.
- Minimize
ruminal pH fluctuations by avoiding slug feeding of grains.
- Reduce feeding
times and labor associated with feeding forages and concentrates
individually.
- Allow for
flexible formulation so adjustments can be made due to changing
forage quality and/or to take advantage of fluctuations in market
and ingredient prices.
- Group and
feed based on different management strategies.
All of the
above have combined to make TMR feeding the prevalent practice in
large herds and it continues to grow in popularity. The multitude
of ingredients used in a TMR also make it one of the most difficult
feed types to subsample. All of the following can influence the quality
(representativeness) of the sample:
- Use of multiple
ingredients (forages, grains, byproducts, minerals) of varying
particle size are often difficult to blend and are prone to separation.
- Lack of moisture
in the ration can lead to separation of ingredients.
- The composition
of individual ingredients can change (forage or concentrate) that
will cause the fed ration to be different from the formulated
ration.
- Mineral-vitamin
premix – was the premix mixed according to specifications
at the plant?
- Protein-mineral-vitamin
supplement – was the supplement mixed according to specifications
at the plant?
- Were the
ingredients in the TMR added in the amounts specified in the ration
formulation?
- Were the
scales working properly?
- Were ingredients
added according to manufacturer recommendations to allow for optimum
blending?
- Was the mixture
allowed to mix for an adequate amount of time to insure complete
blending?
- Fresh samples
should be taken before the cows are allowed access to the feed.
- Multiple
subsamples should be taken and combined to avoid sampling error.
- Was the sample
adequately blended and subsampled at the lab to insure a representative
sample was used for analysis?
All of the above
contribute to the difficulty of obtaining a representative subsample
and often, confusing results. TMR analyses are most commonly used
as a check to determine if the mix is meeting nutrient specifications
and/or to evaluate if the "feeder" is blending the ration
according to specifications. While TMR analyses have their merit,
given the multitude of variables that can influence the results, often
too much weight is placed on the analysis. In many instances, your
forage analysis dollar is better spent reanalyzing and confirming
the nutrient composition of the individual forage ingredients and
making ration adjustments as required. Changes in forage quality and
moisture will have a large impact on the ration. Typically, the result
of a TMR analysis that does not meet specifications will result in
reanalysis of the individual forages, so that you are further ahead
to do this in the first place.
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