We now have a large set of data, both experimental and observational, showing that genetically modified feed is safe and nutritionally equivalent to non-GMO feed. There does not appear to be any health risk to the animals, and it is even less likely that there could be any health effect on humans who eat those animals.
In order to maintain the position that GMOs are not adequately tested, or that they are harmful or risky, you have to either highly selectively cherry pick a few outliers of low scientific quality, or you have to simply deny the science.
Here is a
comprehensive list of animal feeding studies. Many of these studies are independent. The list included systematic reviews, all of which conclude that GMO feed is safe.
There is as strong a scientific consensus that GMOs do not present any novel health risk, that those in current use are safe, and that they pose no health risk to animals or humans, as there is a consensus for the safety and efficacy of vaccines or that humans are contributing significantly to global warming.