Microbiome manipulation
We manipulated the gut microbiome of the fish in the tanks using control
(untreated) feed, antibiotic treated feed and probiotic treated feed:
Antibiotic treatment : Oxytetracycline (OTC), and Chloramphenicol
(CAP), two broad spectrum antibiotics, were selected for the trial.
Twenty-four tanks (for 12 (families)*2 (replicates)) were labelled as
antibiotic and were treated with OTC (83 mg/kg/day concentration) (Kokou
et al., 2020; Rosado et al., 2019) for six days. After six days the fish
were switched to a combination of Chloramphenicol (CAP) (42 mg/kg/day)
(Bilandzic et al., 2012) plus the OTC for four more days, for a total of
10 days of antibiotic treatment. Fish were fed three times a day at
approximately 3% of their body weight.
Probiotic treatment : Twenty-four tanks (for 12 (families)*2
(replicates)) were labelled as probiotic treatment and fed commercially
available Jamieson Probiotic
Complex with 60 billion colony forming units (CFU) (Jamieson
Laboratories, Canada; Supplementary Table S1). Specifically, the
probiotic-treated feed (3 capsules per 100 gram of feed) was coated with
10 mL of sodium alginate (1%) and 10 mL of 0.5 % calcium chloride
prior to mixing with the probiotic powder. Fish were fed three times a
day at approximately 3% of their body weight.
Control : Twenty-four tanks (for 12 (families)*2 (replicates))
were labelled as control group and fish were fed with regular feed
without probiotic or antibiotic for ten days. Fish were fed three times
a day at approximately 3% of their body weight (Fig. 1).