MICROENCAPSULATED ORGANIC ACIDS AND PHYTOGENIC COMPOUNDS IMPROVES TILAPIA SURVIVAL IN PATHOGEN CHALLENGED CONDITIONS

Commercial tilapia production in Latin America and elsewhere had been suffering from frequent disease outbreaks. Traditional bacterial pathogens such as Streptococcus sp., Edwardsiella sp., and Aeromonus sp. along with new influenza like viral pathogens such as tilapia lake virus (TiLV ) have been causing severe mortalities in countries like Colombia.

To address this issue, an experiment was designed to test various potential feed additives.  The fish were challenged with a mixture of pathogens containing Streptococcus agalactiae , Edwarsiella sp. and Aeromonus sp. to produce lesions comparable to the Tilapia Lake Virus (TiLV). To inoculate, the feed was sprayed with the pathogen solution (10 x 10¹² /ml). All fish were then fed with pathogen inoculated feed on the day 28 and then raised for 50 days. Occasionally,  the fish were subjected to stress conditions e.g., elevated temperature (30-32 C) and wide temperature fluctuations (24-32C) to increase their susceptibility to pathogens.

A commercial diet ( negative control, Control ) was used as a basal diet. Three other diets were prepared supplemented with a yeast cell wall containing 36% beta-glucan and 23% mannan-oligosaccharides ( positive control, YCW - 500 g/MT), a microencapsulated organic acid mix (MOA - 800 g/MT), and a microencapsulated mix of organic acids and phytogenic compounds (MOAEO - 500 g/MT). A total of 480 fish were distributed in 16 120-L glass aquarium at 30 fish in each . The trial  lasted for  78 days, 28 days before and 50 days after inoculation .

All three additives showed significant improvement in survival, FCR and biomass gain compared to the control (Fig 1a, 1b, and 1c, respectively). Best survival (91%) was reported in fish fed microencapsulated mix of organic acid and essential oil supplemented diet compared to those fed the MOA (78%) or YCW (79%). However, fish fed the control diet had only 49% survival.