while using limits please read the articles in the regulations carefully, especially on the definition, what is food under food law pespective (or what is feed)
We are food manufactures. Limits are applicable only if it can be demonstrate that a contamination up to 0,9% is adventitious or technically unavoidable. Otherwise or above the limit declaration is necessary. The basis is zero-contamination. For some labels in EU or US there are some additional requirements (feed, enzymes, vitamins, flavours).
For feed it is slightly different especially since a technical solution for non-registered variants is in place. But the principle is the same.
Feeding of animals with GMO is excluded from declaration in the EU. Some labels are asking for that ("ohne Gentechnik" in Germany or "nonGMOproject verified" in the US) and than sourcing of feed becomes of interest. Have a look on IP certificates or organic sources.
You should be aware that the legal requirement focuses in Europe since more than 10 years primarily on documentation, not on analytic. You will not detect foreign DNA in vitamins or glucose syrupe.