So along the lines of maintenance and conversion I thought I would add some reference in order to provide context, pique your curiosity, and hopefully encourage your desire to study and learn. But mostly, I would like to encourage your curiosity and encourage you ask yourself questions that spur further discovery.
We may conclude that the principles of feeding tell us that maintenance inhibits the conversion of feed and so we come away with the understanding that there exists a goldilocks Specific Feeding Rate (SFR) that optimizes the Gross FCR for a fish at a given stage of development. Just a casual glance at the Gross FCR vs SFR Chart tells us that the intrinsic FCR is reached at an infinite SFR. But common sense tells us that our typical fish can't eat its own weight every day let alone an infinite weight of feed. So we know there are physical/natural limits. Further careful thought also tells us that retention in the gut could also be important to conversion and if too much were consumed on a daily basis that it is possible that the efficiency of assimilation could be compromised.
This SRAC publication tells us that :
Under most circumstances, fish need to be fed less than they will eat. Overfeeding will cause the fish to use the feed less efficiently and will not increase growth rates signficantly
It includes an SFR table that out lines feeding rates at various stages of growth (fish size as expressed in number per pound). A table like this is specific to "a feed" and "a species" and can generally be obtained from the feed manufacture for the formulations designed for the farmed fish. Big producers sometimes develop their own tables and design and formulate their own feeds. To do so economically requires economy of scale.
![[Linked Image]](https://forums.pondboss.com/ubbthreads.php?ubb=download&Number=18349&filename=SFR Chart.jpg)
The same publication mentions the rainbow trout Specific Maintenance Rate at temps below 38 F:
The minimum temperature for growth in trout is about 38 F. At this temperature and below, appetites are suppressed, digestive systems operate very slowly, and trout require only a maintenance diet (0.5 to 1.8 percent of body weight per day, depending upon fish size). Feeding more than this wastes feed.
Now I was very surprised to see a maintenance rate (SMR) as high as 1.8 percent of body weight but glancing at the left most SFR column in the table it made more sense. While this column "anticipates growth" we might reasonably infer that smaller fish could have greater metabolic requirements that require a higher maintenance rate.
