Despite the doubts about probiotics – Due to unrealistic claims, poor quality products or mode of delivery – appropriate probiotics do actually work in aquaculture production.
Olivier Decamp and David Moriarty explain
Aquaculture is developing and intensifying in most regions of the world in response to the increasing demand for aquatic food products (FAO, 2006). This intensity has led to an increased use and misuse of drugs and chemicals in aquaculture, resulting in food safety concerns. Several alternative strategies to the prophylactic use of antibiotics in disease control have been proposed: installment of biosecurity management, effective vaccination, stimulation of the non-specific defense mechanisms of the host (alone or in combination with vaccines), as well as microorganisms (probiotics). Defining probiotics is a challenge – even more so for aquaculture applications. Historically, probiotics were defined according to their expected benefit or improvement to the host’s intestinal balance. Being concerned with humans and terrestrial animals, probiotics were generally Gram-positive obligate or facultative anaerobes, mostly lactic bacteria.
Fish are different
Aquatic animals differ from terrestrial animals in the level of interaction between the intestinal microbiota and the surrounding environment. The bacteria present in the aquatic environment influence the composition of the gut microflora and vice versa. This environmental influence is much greater for shrimp and other invertebrates than for fish. The bacterial community composition of the intestinal tract of aquatic animals is different from that found in terrestrial animals. Gram-negative facultative anaerobes generally prevail in the digestive tract of fish and shellfish; Gram-positive obligate or facultative anaerobes dominate that of humans and terrestrial animals (Gatesoupe, 1999). Aquatic animals are poikilothermic and their associated microbiota may vary with temperature changes; salinity changes in the rearing environment will also affect the microbiota. An important consequence is that the most efficient probiotics used for aquaculture will differ from those for terrestrial species.