Generally, a control feed is selected if it is in practice. So, with this if, you compare other formulated feeds then a good comparison between the existing control feed and the formulated feed can be done.

Dear Judine,

A "control" diet for fish growth or reproduction should be chosen on a case by case basis and I think this choice depends on the answers you're looking for. What do you want to use this "control" for? For instance, if you're looking for an optimized diet to be used in aquaculture, I think it can be interesting to include diet specifically designed for reproduction of your species (e.g. manufacturer), if such a diet exists. Note that this diet would be more like a benchmark than a real control diet and I think you should consider whether the claim of the manufacturer is really reliable. It can also be interesting - if technically feasible - to include the natural food your species is used to, as a benchmark as well. However, comparing a dry diet with a wet diet also has its limits because of the huge difference in energy density, but it's better than nothing. Keep in mind that all species are different and their nutritional requirements often differ greatly from one to another. That's my personal view on this topic. Others may have different views on this.

Best regards,

Neil

Diet as control should be used what diet is in practice, which you think is not a complete feed or has some problem with nutritive value or high cost or other limitations ... and, which you want to compare with your new formulate feed to change for improvement as better growth, or better health or better income for high profit etc.

Dear Judine:

As the others have mentioned, your choice of the control feed has some options. In general, I'd agree with Mr. Esmaeili that the diet needs to be more of an optimum, since your experimental diets will be comparing growth, survival, etc. from this "baseline" diet.

In the second question, you ask if you can use a feed prepared by a commercial supplier. This may be more difficult. Most commercial mills manufacture diets based on a "least cost" formulation which involves the substitution of ingredients based on cost and availability. In that case, the formulation may change from batch to batch. This, then, would not be a suitable product to use as your control...because you might end up using different feeds for your experiments.

If the mill will provide you the formula, that may be helpful. Even then, you would be best to be at the mill during manufacturing to verify the ingredients are being used as expected. My suggestion is to confirm the best common formula for your area, including ingredients, and be at the mill to verify the feed being produced meets your expectations. In this way, you can be certain your control feed is as you expect.