EFFECT OF GRADED LEVELS OF A HERBAL STIMULANT, AQUAPRO®, ON GROWTH AND INTESTINAL MORPHOLOGY IN JUVENILE DUSKY KOB Argyrosomus japonicus

The need and the desire for aquaculture researchers to shift away from synthetic drugs in aquaculture, has prompted a search to find alternative additives in fish diets. The current study was therefore designed to test the effect of a commercial herbal product, Aquapro^®on the growth performance and gut morphology of the South African juvenile dusky kob, Argyrosomus japonicas (Sciaenidae) in a seven week feeding trial. Four isonitrogenous diets, consisting of three Aquapro^®-containing diets at rates of 0, 50, 100, and 150 g/kg DM (Aqua0, Aqua50, Aqua100 and Aqua150, respectively) were formulated. Forty five fish (14.44 ± 0.27 g) were randomly distributed into each of the 12 experimental tanks in preparation for the commencement of the experiment.

Each dietary treatment was randomly allocated to three tanks and offered to fish at a rate of 2.8% body weight. A total of 10 fish from each tank were randomly sampled once a week for length and weight measurements to monitor weekly growth performance. At the end of the experiment (week seven), three fish from each tank were humanely sacrificed to sample distal intestinal tissues for histology preparation. Repeated measures analysis revealed a non-significant (P > 0.05) interaction between the diets and the fish age (weeks) on both the weight and caudal length of the experimental fish. The fish weight gain decreased significantly with an increase in Aquapro^® inclusion in the diets (Table 1). The highest weight gain of 36.97 ± 1.57 g and caudal length gain of 5.47 ± 0.09 cm were recorded for the control diet after seven weeks. The highest Aquapro^® inclusion level diet produced the least weight gain of 24.57 ± 2.44 g and caudal length of 4.01 ± 0.33 cm. Normal distal morphological structure was observed for all treatment groups. In conclusion, the results show that the Aquapro^®product, up to 100 g/kg kob diet does not negatively affect juvenile dusky kob growth. The product at the investigated level of inclusion does not cause gut inflammation.