Assessing the use of a dietary probiotic/prebiotic as an enhancer of spinefoot rabbitfish Siganus rivulatus survival and growth

The use of prebiotics and probiotics as feed supplements that improve efficiency of intestinal bacteria is becoming de rigueur in animal husbandry in many regions worldwide. We tested the effects of a commercial probiotic (Biogen®) containing allicin, high unit hydrolytic enzyme, Bacillus subtilis spores and ginseng extracts on survival, growth, carcass composition and feed cost/benefit in rabbitfish Siganus rivulatus. Fifteen net cages (100 x 100 x 40 cm; L x W x H) were stocked with 10 juvenile rabbitfish (10.3 g per fish) each and placed in a large rectangular tank and offered feed at 4% body weight daily. Cages were offered one of five isonitrogenous and isocaloric diets containing 0, 1, 2, 3 and 4 g kg⁻¹ probiotic at three replicates per treatment for 98 days. Fish in all cages were weighed at 2-week intervals and feed regimen was adjusted accordingly. Rabbitfish offered the control diet exhibited lower growth and feed utilization than all experimental treatments. There was no effect of probiotic inclusion level on survival but growth was better at all inclusion levels than in the control. No significant differences (P > 0.05) in growth were observed among fish groups fed various levels of the probiotic. Carcass composition was not affected by dietary probiotic inclusion. Ultimately, when all variables are considered, Biogen® inclusion to diets appears to reduce feed cost per unit growth of rabbitfish.