Here are some of my thoughts and rationale why to stock expensive trout just to feed bass.
I think the rationale for using trout is to feed the bass larger than 6-8lbs to give them adequate food to push them toward and over the 10lb mark. It is supplemental forage. The trout due to overall nutrient content will produce slightly better weight gain compared to bass eating FHM & GSH. Also FHM and GSH will not put weight gain on the biggest bass.
Here's an example: For $14 I can get 1 dozen trout 5-8" in size, or for $17 I can get 1 pound of minnows 3-4" in size. There are about 50 minnows in 1 pound this size.
During August and September 2014 I fed my LMB these 3-4" minnows. They picked them off as they saw them. I fished with these same minnows and landed some LMB.
During October and November 2014 I fed these same LMB trout fingerlings 5-8" in size. Just as with the minnows, the LMB would hit the trout immediately. And I also used some trout to land some LMB.
My observations without using a scale or a measurement stick and relying solely on my eyes and comparing photographs snapped of the landed LMB is that as the water temperatures cooled in October and November the size of these LMB did not hold steady or regress (in weight), but instead the LMB gained weight.
Note that I have less than 16 LMB in this pond so I'm very familiar with the LMB due to their markings and sizes. My LMB have always appeared healthy - there is plenty of forage for them to dine on and not much competition.
While I don't have a weight and measurement chart, I can recall from the photographs and memories of landing the LMB that the LMB certainly appeared to gain more weight dining on the trout compared to the minnows. I also know that a healthy 5" trout has more body mass than a healthy 5" minnow (at least of the ones I stocked). The LMB were thicker and their bellies plumper in late October and through November. I've watched 14" LMB swallow 8" trout.
