.Lactobacillus plantarum 44a as a live feed supplement for freshwater fish
Many studies show that the ingestion of Lactobacillus species as probiotic improve host health. In this thesis, the natural presence of Lactobacillus in the gastrointestinal tract of some common freshwater fish inhabiting the river Maas and the absence of Lactobacillus in some farmed fish is described. In order to select a Lactobacillus strain to be used as feed supplement for farmed fish, Lactobacillus plantarum 44a was selected by inhibitory abilities towards pathogens in vitro, by survival to the exposure to gastrointestinal fluids and resistance to dehydration and storage in feed. An experiment was set up to study the transit time of L. plantarum 44a from feed to faeces of tilapia (Oreochromis niloticus). L. plantarum 44a was excreted as pulses dependent on the dosage ingested and periodicity dependent on the frequency of Lactobacillus consumption.L. plantarum 44a ingested on the highest dose tested became the dominant strain in the intestine. Other observations suggest that L. plantarum 44a enhances the natural defenses of fish and may prevent infectious diseases. As a whole conclusion L. plantarum 44a is a promising probiotic species in aquaculture.