Assessing the effectiveness of complex dietary candidate probiotics on growth performance, digestive enzyme activity, antioxidant capability, and intestinal microbiota of koi carp (Cyprinus carpio var. koi)

Abstract

The present study aimed to evaluate the effectiveness of three complex dietary candidate probiotics (LDJ, LAC, and LJD) composing different candidate probiotic combinations on the growth performance, digestive enzyme activities, antioxidant parameters, and intestinal microbiota in koi carp (Cyprinus carpio var. koi). After a 60-days feeding trial, samples from the control and three candidate probiotic groups were obtained and analyzed. The results suggested that all complex dietary candidate probiotic treatments (LDJ, LAC, and LJD) improved the growth performance, nutrition utilization, and intestinal digestive enzyme activities compared with the control group. Furthermore, a dietary supplement with LAC or LJD is more efficient in growth and digestive enzyme than LDJ. The antioxidant enzyme activities, including SOD (superoxide dismutase), CAT (catalase), and GPX (glutathione peroxidase), were intensively improved, the GSH (glutathione) contents increased, and the MDA (malondialdehyde) contents decreased to different extents depending on the tissues and kinds of candidate probiotics. Dietary candidate probiotics also regulated the intestinal microbiota composition: LDJ and LAC increased the proportion of potential candidate probiotics and reduced the level of pollutants reducing bacteria and geosmin producer Nannocystis. The LJD group had a similar pattern of the dominant bacteria to the control sample, suggesting a minor disturbance of the gut microbiota of koi carp. Overall, the multi-strain complex candidate probiotics LAC and LJD are more efficient in growth performance and digestive enzymes.