Title : Spray coating: Small scale method to incorporate potential probiotics in feed
Abstract:
Probiotics are increasingly studied in fish nutrition for their role in enhancing health and reducing antibiotic use. Nonetheless, the efficacy of probiotics in aquaculture diets is influenced not only by the selection of the microorganism species but also by the feed processing methods, which directly impact microbial viability. Conventional extrusion, widely used in commercial fish feed production, can compromise probiotic survival due to elevated temperature and pressure conditions, and standardized methods for experimental feed incorporation remain scarce. Therefore, incorporating live microorganisms directly (in natura) into the feed, without requiring additional processing steps such as drying or microencapsulation, can simplify feed preparation while maintaining microbial viability and ensuring effective functionality in the fish gastrointestinal tract. Hence, the spray coating method was tested as a strategy to directly incorporate potential probiotics in aquaculture feed, using the yeast Phaffia brasiliana UFMG-CM-6497, and the supplemented feed was administered to Nile tilapia (Oreochromis niloticus) for 9 weeks in both Clear Water (CW) and Biofloc (BFT) systems. During a seven-day storage trial, the concentration of 106 CFU/g remained remarkably stable (p>0.05), indicating minimal microbial loss when using this method. Additionally, feed moisture remained below the 15% threshold recommended by the FAO, measuring 13.8% immediately after spray coating and 12.2% after 24 hours, which allowed effective dilution of the microbial solution for homogeneous distribution while preserving the feed’s physical integrity. When 300 pellets were administered in water to test microbial concentration maintenance – simulating practical feeding conditions – 106 CFU/g was maintained at 0, 1, 3, 5, and 10 minutes. Additionally, the feed pellets exhibited buoyancy of 90% (within the established standard of 80-85% floating) and good hydrostability, preserving their structural integrity throughout the test. The yeast was recovered from the intestinal content of fish in all treatment groups that received it, in both CW and BFT systems, and its survival was confirmed through the observation of characteristic Phaffia colonies, demonstrating that spray-coated feed effectively maintained microbial availability until consumption. Overall, these results indicate that spray coating is a viable, efficient, and scalable method for incorporating probiotics into fish feed, maintaining microbial viability and concentration, ensuring feed quality, and providing a practical solution for routine use in research laboratories, particularly due to the absence of prior processing and the direct in natura application.
