Cargill is good feed with good conversion in LMB and BG. It is very dollar efficient for the conversion as well. I am referencing Greg Grimes findings where under his analysis it only slightly underperformed the Purina (MVP I think). Cargill IIRC provided conversion at the lowest cost. I'll link that page later as I am traveling.
Its hard to argue that protein is protein and so I do think fish based lipids and proteins are better ... But for aquaculture acceptable cost efficient alternatives are essential to sustainable feeds. So I see Cargill as a feed worthy of consideration.
Steve_, could you reference the source saying fish meal is not an additive of Cargill feeds? Most manufactures are very reluctant to speak about feed formulations. Also, I am reluctant to accept any claim that protein is sourced only to fish in any particular feed. In the end, if one feeds there will be a conversion/maintenance benefit. Where the focus is recreational, the difference in feeds isn't all that noticeable. In aquaculture, the difference is an economic effect that deserves much deeper consideration.