Study of microbiocenosis of fish gills and intestines in their cultivation using preparations based on bacteriophages

Nowadays bacteriophages are widely used in veterinary medicine, bio-technology, agriculture and in particular in aquaculture. Narrow specificity affecting the bacterial microflora and selective influence on the pathogenic and opportunistic microorganisms allow using the bacteriophages for diagnosing, preventing and treating the diseases of farm animals and fish. The emergence of antibiotic-resistant strains of microorganisms involves the search for new drugs to combat them. In this regard, phage therapy is an alternative to antimicrobial treatment of bacterial diseases of animals and fish. Despite the lack of data on the bacteriophage-based drugs applications in aquaculture, this direction is found to be promising and relevant. There is given a comparative analysis of the microbiocenosis of the gills and intestines of two-year-olds of red tilapia farmed in the water with adding the poly-valence pyobacteriophage and fed by compound feed treated by the preparation. It has been found that the dominant position in the intestinal microbiocenosis of red tilapia belongs to Micrococcus bacteria, whose share made 45.7% of all isolates of the gastrointestinal tract. By the frequency of occurrence, the second place is taken by the Bacterium species (33.2%), the third place - Staphylococcus (16.1%) species. The remaining groups of intestinal microorganisms are presented by a significantly number of isolates. It has been stated that the gills microflora was represented by a smaller species composition compared to the digestive tract microbiota. Isolates of the Bacterium and Staphylococcus bacteria were dominating, while the Actinomycetales and Bacillus microorganisms were represented in smaller numbers (1-2 colonies). The addition of a bacteriophage to water and its processing of compound feed helps to reduce the contamination of gills and reduce pathogenic microflora in the intestines of fish.

Assessment of Tilapia–Freshwater Prawn Co-Culture Schemes in Tanks and Lake-Based Cages for Increased Farm Production

The technical viability of tilapia (I-ExCEL strain Nile or red) and giant freshwater prawn (GFP) co-culture in cages-within-tanks was evaluated while appropriate feeding protocols for tilapia-GFP co-culture in cages in a eutrophic lake were determined. Specifically, production parameters in all test species grown for five months in tank co-culture (where only tilapias were fed) were compared, while the best feeding protocol from among the following treatments: (a) Tfed—fed tilapias; (b) GFPfed—fed prawns and (c) T-GFPfed—both species fed, were defined. I-ExCEL Nile tilapias grew faster in tank co-culture whether reared singly or otherwise. However, red tilapia-GFP tank co-culture gave the best results considering key production traits in all test species (red tilapia —2.52%/day specific growth rate or SGR, 83.3% survival; GFP—1.17%/day SGR, 72.85% survival). Lake-based co-culture was technically feasible at stocking densities of 12.5/m2 for tilapia and 2.4 to 4/m2 for prawns even when only tilapias were fed; prawns grew to desired marketable sizes by thriving mainly on detritus and natural food organisms in the lake. However, further refinements can still be made to optimise the co-culture schemes to make them more sustainable and provide artisanal fish farmers options in increasing farm yields through multi-species aquaculture.

Bioconversion of Coconut Testa by Rhizopus Oryzae on Chemical Changes and Performance of Red Tilapia (Oreochromis Niloticus)

The nutritional content that is balanced and in accordance with the needs of fish will be utilized by fish as a source of energy used for growth. The used of feed alternative from coconut testa bioconversion has been investigated for its effect on the growth performance of red tilapia stadium fingerling. The chemical composition of coconut testa, survival rate and water quality (temperature, pH and dissolved oxygen) were analysed descriptively. The experiment was carried out experimentally using a Completely Randomized Design (CRD), which consisted of four levels of using coconut testa bioconversion by Rhizopus oryzae in feed (0%, 5%, 10%, 15%, and 20%). The performance parameters measured consisted of Average daily gain, feed efficiency, and protein efficiency ratio. Data were analyzed using the Analysis of Variance (ANOVA) with a 95% confidence level, and Duncan's multiple distance test. The chemichal change, survival rate. The study showed that the bioconversion of R. oryzae coconut testa up to 20% in the feed formulation could provide the performance of red tilapia fry, with the highest value obtained at the use of 15% with an average feed efficiency of 42.43 ± 0.71.