The effects of dietary Lactococcus spp. on growth performance, glucose absorption and metabolism of common carp, Cyprinus carpio L.

Abstract

Based on beneficial effects of Lactococcus spp. and their extracellular polysaccharides on common carp (Cyprinus carpio L.) in previous studies, the main purpose of this paper was to investigate the functions of single or multi-strains of Lactococcus spp. on the growth performance, glucose absorption and metabolism of common carp. The results showed that when the fish consumed diets containing single (Lactococcus lactis Q-8, L. lactis Q-9, L. lactis Z-2) or multi-strains of Lactococcus spp. (5 × 108 CFU g−1 of feed) for 60 days, the final weight, weight gain (WG), specific growth rate (SGR) and condition factor (CF) had significantly (P < .05) increased, especially in the multi-strains addition groups. While the feed conversion ratio (FCR) of all Lactococcus spp. addition groups was significantly lower than that in the control group (P < .05). Viscera-somatic index (VSI) and survival rate in each experimental group was no significant difference during the feeding period (P > .05). For the glucose absorption, Lactococcus spp. addition groups significantly increased the blood glucose concentration and up-regulated the expression of Sglt1 and Gult2 in intestine compared with the control group (P < .05). In addition, the contents of hepatopancreas glycogen were also significantly increased in the Lactococcus spp. addition groups (P < .05). For the glucose metabolism in hepatopancreatic, the Lactococcus spp. addition groups significantly decreased the expression of GK and PK in glycolysis (P < .05), while increased the G6Pase and PEPCK expression in gluconeogenesis (P < .05). Furthermore, with the prolongation of feeding time, the synergistic effects on the expression levels of absorption and metabolism related genes, and the glycogen content were better in the multi-strains addition groups. Overall, these results suggested that the Lactococcus spp. improved the growth performance, and exerted glucose absorption and metabolism effects in common carp, which provide a theoretical basis for the rational use of potential probiotics and carbohydrate in aquaculture.