Revised Gamefish Grow Fish Meal
49.2% protein, 18.2% fat, 20.9% starch, .8% fiber, 10.9% ash
Purina Aquamax Grower 500
41.3% protein, 12% fat, 31.7% starch, 4% fiber, 11% ash
Protein Waste: Gamefish 49.2 x .91 digestible protein = 44.7
49.2 - 44.7 = 4.4% waste
Aquamax 41.3 x .94 digestible protein = 38.8
41.3 - 38.8 = 2.4% waste
All fat is either used for energy or stored
Starch Waste: Gamefish 20.9 - 20 = .9% waste
Aquamax 31.7 - 20 = 11.7% waste
All Fiber is passed Gamefish .8% waste
Aquamax 4% waste
Ash is used at around 7% - 8% Gamefish 10.9 - 7.5 = 3.4% waste
Aquamax 11 - 7.5 = 3.5% waste
Total Waste: Gamefish 9.5% waste Aquamax 21.6% waste
That's better. Waiting on fish meal prices from my local co-op. This formula is closer to the Purina 50% protein food.
I think adding more protein might not make a difference to the fish. I found this article that says rainbow trout showed no growth differences when fed diets with protein contents of 41% and 56.5%. If there are no growth differences then the fish aren't utilizing all the digestible protein they are fed. The abstract says "These results indicate that the limit to which rainbow trout can metabolize protein to increase growth may have already been reached, and that any future increases in protein in commercial feeds may not affect the growth rates."
What the fish don't utilize becomes waste. So, the feed with the higher protein content will have more wasted protein. Protein waste is expensive waste. This may be why Purina chooses to use the amount of protein they do.
