How many will you need to raise to feed one person? How many bugs will be needed to feed many people? Then the most important question, how do you deal with the fact that bugs are a terrible source of nutrients?

1 cow if infected can and will have thousands if not millions of parasites/bacterium/viral loads because of the increased mass present.

That's one hell of an emotional response. You're also completely ignoring the fact that a single tainted bug can effectively poison what ever batch it's put into. A single diseased cow can also be easily identified, and then separated from the herd and put down.