EFFECTS OF MULTISTRAIN PROBIOTICS ON THE GROWTH, BEHAVIOR, AND GUT HEALTH OF JUVENILE RED DRUM Sciaenops ocellatus  

Probiotics are defined as a "good bacteria." Important to a functional digestive system, the use of probiotics has become more common in the last 10 years to help re-establish the gut flora after a treatment of antibiotics. Red drum (Sciaenops ocellatus) a commercially important carnivorous marine fish have a short gut and fast transport. Rapid digestion and assimilation rates are important to rapid growth. The current study was conducted to determine the effects of probiotics on growth rates, behavioral patterns, and evaluate gut health, and will in the future include assessing the composition of gut microbiome. Together these investigations will provide an index of health of the red drum while being treated with probiotics, in order to determine if probiotics is a viable sustainable alternative to antibiotics as a growth enhancer.

A 28 day feeding trial was conducted in 20 gallon tanks inside a temperature controlled room at 27°C. Juvenile red drum from APEKS Aquaculture® (Palacios, Texas) were measured and weighed at the start of the experiment. Experimental tanks were divided into: 1) control, 2) probiotics recommended dosage, and (3) 2x the recommended dosage. Probiotics selected was Primilac® a multi strain mixture containing Lactobacillus acidophilus, Lactobacillus casei, Bifido bacterium bifidium, Enterococcus faecium. Probiotics was added to treatment tanks daily along with the fish meal, while controls were only fed fish meal. Once per week, three fish were sampled, weighed, and measured. Their overall body condition was assessed and catalogued. The fish were then sacrificed for gut microbiome analysis.

After 28 days, the fish fed with the recommended dosage of probiotics showed a growth increase of 18% compared to controls (Fig. 1). All fish in the 2x treatment fish died by day 16 (Fig. 1). Several interesting behavioral and physical appearance observations were noted; 1) the fish in the probiotics groups rarely nipped at each other, and caudal fins were undamaged. In contrast the control group (no probiotics), 1) nipped each other frequently, 2) often reducing other fish's caudal fins to nubs and 3) red bite whelps occurred at the dorsal fin. The mediating effects of probiotics on aggressive behavior will be tested in future work, as these behavioral modifications may be significant in aquaculture where aggression is common due to overcrowding.