Digestive bacteria and probiotics
The digestive systems of larval marine fish are very immature when the larva fish first begins feeding. Digestive bacteria present in live feeds are critical for establishing the digestive bacteria of the larval fish. Thus, rotifers have a probiotic effect for larval fish.
This probiotic effect is connected to but should not be confused with probiotics used for culturing rotifers. Having the right probiotic bacteria is an important aspect of culturing rotifers and keeping rotifer cultures clean and healthy. Undoubtedly, clean and healthy rotifers with beneficial pro-biotic bacteria have a critical impact on the cleanliness and health of larval fish. This topic is addressed further in the section on production.
Digestive enzyme deficiencies and anabolic enzyme deficiencies
Larval fish can be deficient in digestive enzymes, so the digestive enzymes in live feeds can provide a critical boost for nutritional uptake, growth and survival.
Yet, digestion (catabolism), the breakdown of food, is not the only critical enzymatic function. Enzymes are critical for the creation of new tissue from digested nutrients (anabolism).
It has been strongly suggested by Sargent and Touch and other researchers that enzyme deficiency in larval fish can significantly effect tissue creation. In particular, larval fish can lack sufficient enzymes to fully utilize oily feeds for the creation of cell membranes. It is likely that enzyme depletion is a problem for other nutritional factors as well. Enzyme depletion in the context of lipid synthesis is addressed in the next section.