Variations in nutritional values of poultry feed ingredients

It is well known that there are always variations in nutrient values of feed ingredients.

There are many reasons which may contribute to this variability. Sampling and analytical methods are among the important ones although all agricultural circumstances (under which these ingredients are produced and processed) can play an important role as well.

If we send same ingredient or feed samples to two different laboratories for analyses, we may get different results.

How do you deal with this problem at your feed mill or poultry farm?
How often do you submit ingredient and feed samples to laboratory for analyses?
Do you formulate your rations based on results (nutrient values) that you get from a laboratory or also get help from you previous experiences?

There are many factors which can affect flock performance but do you monitor performance of your flocks with respect to diet’s formula?

Do not hesitate to give your point of view or your experiences here.