Effects of Supplementing Intestinal Autochthonous Bacteria in Plant-Based Diets on Growth, Nutrient Digestibility, and Gut Health of Bullfrogs (Lithobates catesbeianus)

Abstract

Poor utilization efficiency of plant protein diets always leads to intestinal barrier dysfunction and growth inhibition in animals. Probiotics have shown promise in improving growth performance and gut health of the host. However, obtaining the host-beneficial probiotic from thousands of bacterial phylotypes is challenging. Here, four intestinal autochthonous bacteria were isolated from fast-growing bullfrog after a 60-day feeding on a soybean meal (SM)-based diet. Another feeding trial was conducted to evaluate the effects of supplementing these strains in an SM-based diet on growth, nutrient digestibility, immunity, and gut health of bullfrog. A high-SM basal diet was used as a non-supplemented control group (NC), and four other diets were prepared by supplementing the basal diet with 1 × 107 CFU/g of Bacillus siamensis, Bacillus tequilensis (BT), Bacillus velezensis, and Lactococcus lactis (LL). Results showed that weight gain, feed efficiency, nitrogen retention, and apparent digestibility coefficients of dry matter and protein were significantly higher in the LL group compared with the NC group (p < 0.05). Furthermore, compared with the NC group, both BT and LL groups showed markedly higher jejunal protease and amylase activities, serum complement 4 and immunoglobulin M levels, jejunal muscularis thickness (p < 0.05), and up-regulated expression of il-10 and zo-1 genes (p < 0.05). High-throughput sequencing revealed higher abundances of Bacillus and Cetobacterium in BT and LL groups, respectively, accompanied with decreased abundances of Enterobacter and Escherichia–Shigella. Besides, KEGG pathways related to metabolisms were significantly enhanced by the LL diet relative to the NC diet (p < 0.05). Overall, the beneficial effects of two frog-derived probiotics were determined: supplementation of L. lactis in SM-based diet promoted growth and nutrient digestibility; both B. tequilensis and L. lactis supplementation improved immune response and intestinal barrier function of bullfrogs.

Physiological Response of Spotted Seabass (Lateolabrax maculatus) to Different Dietary Available Phosphorus Levels and Water Temperature: Changes in Growth, Lipid Metabolism, Antioxidant Status and Intestinal Microbiota

“…Intestinal microbiota play an important role in the health, immunity, metabolism, development, and reproduction of fish [73]. Dietary nutrition is a critical factor in determining the makeup of the trillions of bacteria that reside in the intestine [74]. Labaw et al [75] demonstrated that P, as a component of nucleic acid and other biochemical molecules, played a vital role in microorganism growth [76].…”

Blue and Red Light Color Combinations Can Enhance Certain Aspects of Digestive and Anabolic Performance in Juvenile Steelhead Trout Oncorhynchus mykiss

“…The commercially available kits (Nanjing Jiancheng Bioengineering Institute, Nanjing, China; A045-4-2, A054-2-1, C016-1-1, A080-2-2, and A080-1-1) were used to determine the total protein content and the activities of lipase, amylase, trypsin, and pepsin in tissues. The total protein content, lipase and amylase activity, and trypsin and pepsin activity were determined as described by Wang et al (2021b), Lu et al (2020), and Zhang et al (2020b), respectively. The determination process was strictly based on the instructions, and absorbance values of total protein content, lipase, amylase, trypsin, and pepsin were measured at 562, 580, 660, 253, and 660 nm, respectively, using a microplate reader (Synergy2; BioTek Inc., USA) and a UV spectrophotometer (UV-5100; Shanghai Metash Instruments Co., Ltd, Shanghai, China).…”