Based on the beneficial effects of Lactococcus spp. and their extracellular polysaccharides on common carp (Cyprinus carpio) in previous studies, a team of Chinese researchers evaluated the functions of single or multi strains of Lactococcus spp. on the growth performance, glucose absorption and metabolism of common carp.
Results showed that when fish fed on 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, specific growth rate and condition factor had significantly increased, especially in the multi strains addition groups. The feed conversion ratio of all Lactococcus spp. addition groups was significantly lower than that in the control group.
Viscera-somatic index and survival rate in each experimental group had no significant difference during the feeding period. For glucose absorption, Lactococcus spp. addition groups significantly increased the blood glucose concentration and up-regulated the expression of Sglt1 and Gult2 in the intestine compared with the control group. In addition, the contents of hepatopancreas glycogen were also significantly increased in the Lactococcus spp. addition groups. For the glucose metabolism in hepatopancreatic, the Lactococcus spp. addition groups significantly decreased the expression of GK and PK in glycolysis, while increased the G6Pase and PEPCK expression in gluconeogenesis.
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.
Researchers suggested that 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 carbohydrates in aquaculture.
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