Effects of Nano-sustained Release Sodium Butyrate on Growth and Intestinal Cell Proliferation of Grass Carps

Taking grass carps with the initial weight of about 20 g as the research object, the basic feeds of grass carps were added with 0.0%, 0.1%, 0.3%, 0.6%, 0.8%, and 1% of nano-sustained release sodium butyrate to prepare 6 types of experimental feeds with equal nitrogen and energy. The effects of different concentrations of nano-sustained release sodium butyrate were surveyed on growth and intestinal cell proliferation of grass carps. The experiment was carried out in cages with 50 carps per cage, and each treatment was repeated 3 times for 60 days. Experimental results indicated that the addition of nano-sustained release sodium butyrate significantly promoted the growth of grass carps and significantly increased the ratio of intestinal villus to crypt depth. When the addition of nano-sustained release sodium butyrate was 0.6%, the weight increase rate, specific growth rate, fullness and intestinal villus height of grass carps were the highest, which was significantly higher than that of the control group (P <0.05). The study results indicated that addition of appropriate amount of nano-sustained release sodium butyrate can promote the growth of grass carps through increasing the intestinal villus height, and the suitable addition dosage was 0.6%

Effects of dietary soy isoflavones on growth, antioxidant status, immune response and resistance of juvenile grass carp (Ctenopharyngodon idella) to Aeromonas hydrophila challenge

The current study was conducted to evaluate the effect of dietary soy isoflavones (SI) on growth performance, antioxidant status, immune response and resistance to Aeromonas hydrophila in juvenile grass carp (Ctenopharyngodon idella). Six diets were formulated to contain 0 (control), 10, 50, 100, 500 or 1,000 mg SI per kg feed. Each diet was randomly allotted to triplicate net cages, and each net cage was stocked with 30 fish. The fish were fed one of the experimental diets to satiation twice per day for 60 days. The results showed that the WGR and DGC of the 500 mg/kg SI-supplemented group were significantly higher than those of the non-SI-supplemented group (p < .05). Serum LZM and IgM activities in the SI-supplemented groups were improved compared to the control group. SOD and GSH-Px levels of fish fed the diet containing 500 mg/kg SI were significantly enhanced compared to those of fish fed the control diet (p < .05). Additionally, serum CAT, GSH-Px and AKP activities in 50, 100 and 500 mg/kg SI-supplemented groups were significantly higher than that in the control group (p < .05). The expression of most immune-related genes (including IFN-gamma 2, TNF-alpha, M-CSF2, IL-6, IL-12p40 and IL-4) was significantly affected by dietary supplementation of SI. The group fed with 500 mg/kg SI had the highest 7-day cumulative survival rate after challenge test (p < .05). The current results revealed that dietary inclusion of SI could improve the immune response and resistance against A. hydrophila and the supplementation level is suggested to be 500 mg/kg diet

Molecular Characterization of LKB1 of Triploid Crucian Carp and Its Regulation on Muscle Growth and Quality

Liver Kinase B1 (LKB1) is a serine/threonine kinase that can regulate energy metabolism and skeletal muscle growth. In the present study, LKB1 cDNA of triploid crucian carp (Carassius auratus) was cloned. The cDNA contains a complete open reading frame (ORF), with a length of 1326 bp, encoding 442 amino acids. Phylogenetic tree analysis showed that the LKB1 amino acid sequence of the triploid crucian carp had a high sequence similarity and identity with carp (Cyprinus carpio). Tissue expression analysis revealed that LKB1 was widely expressed in various tissues. LKB1 expressions in the brain were highest, followed by kidney and muscle. In the short-term LKB1 activator and inhibitor injection experiment, when LKB1 was activated for 72 h, expressions of myogenic differentiation (MyoD), muscle regulatory factor (MRF4), myogenic factor (MyoG) and myostatin 1 (MSTN1) were markedly elevated and the content of inosine monophosphate (IMP) in muscle was significantly increased. When LKB1 was inhibited for 72 h, expressions of MyoD, MyoG, MRF4 and MSTN1 were markedly decreased. The long-term injection experiment of the LKB1 activator revealed that, when LKB1 was activated for 15 days, its muscle fibers were significantly larger and tighter than the control group. In texture profile analysis, it showed smaller hardness and adhesion, greater elasticity and chewiness. Contrastingly, when LKB1 was inhibited for 9 days, its muscle fibers were significantly smaller, while the gap between muscle fibers was significantly larger. Texture profile analysis showed that adhesion was significantly higher than the control group. A feeding trial on triploid crucian carp showed that with dietary lysine-glutamate dipeptide concentration increasing, the expression of the LKB1 gene gradually increased and was highest when dipeptide concentration was 1.6%. These findings may provide new insights into the effects of LKB1 on fish skeletal muscle growth and muscle quality, and will provide a potential application value in improvement of aquaculture feed formula

Effect of Tributyrin on Growth Performance and Pathway by which Tributyrin Regulates Oligopeptide Transporter 1 in Juvenile Grass Carp (Ctenopharyngodon idellus)

The nutritional functions of tributyrin (TB) have been extensively studied, but questions remain regarding its influence on the growth of juvenile grass carp (Ctenopharyngodon idellus) and the regulation pathway to PepT1 in the intestine of grass carp. To answer the remaining questions, feeding trials, cell trials, and peritoneal injection trials were conducted in this study. The results showed that an appropriate level of TB (0.5 g/kg and 1.0 g/kg) supplementation in feed significantly promoted the growth performance of juvenile grass carp. The expressions of intestine genes (CDX2, SP1 and PepT1) related to oligopeptide transportation increased in the 0.5 g/kg TB group of feeding trials and both the 5 mM and 10 mM TB groups of the intestine cell trials, respectively. Subsequently, the injection trials of inhibitors CDX2 and SP1 demonstrated that the inhibition of CDX2 or SP1 decreased the mRNA expression of PepT1. Finally, the results of independent or combined treatments of TB and the inhibitors suggested that CDX2/SP1 mediated TB regulation on PepT1. These findings may help us to better understand the functions of TB on growth and PepT1 oligopeptide transportation, which could be modulated by dietary TB through the CDX2/SP1-PepT1 pathway in juvenile grass carp

The influence of acute ammonia stress on intestinal oxidative stress, histology, digestive enzymatic activities and PepT1 activity of grass carp (Ctenopharyngodon idella)

This study was conducted to evaluate the effect of acute ammonia stress on intestinal oxidative stress levels, histology, and activity of digestive enzymes and oligopeptide transporter 1 (PepT1) in grass carp. Three concentrations of ammonia nitrogen: 0 mg/L total ammonia nitrogen (TAN) (the control group), 1.7 mg/L TAN were used in the present study. Fish were sampled at 0 h, 12 h, 24 h, and 48 h after exposure to ammonia. The results showed that the activities of reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT) and the content of cortisol were all increased in fish exposed to the two concentrations of TAN. Compared with the control group, the activities of intestinal trypsin and chymotrypsin significantly increased in the 1.7 mg/L TAN group, while amylase activity was significantly suppressed in the 50 mg/L TAN group. After ammonia exposure, the expression of intestinal Nrf2 gene significantly increased in the 1.7 mg/L TAN group while the expression of Keap1 gene significantly increased in the 50 mg/L TAN group. Moreover, the expression of intestinal PepT1, Sp1 and CDX2 significantly increased after fish exposed to 1.7 mg/L TAN. The width of mid-intestine villi of fish from the 50 mg/L TAN group was significantly higher than fish from the other two groups. Meanwhile, the area density of PepT1 in the 50 mg/L TAN group was significantly smaller than that in the control and 1.7 mg/L TAN groups. The results suggested that ammonia stress induces intestinal oxidative stress, and 1.7 mg/L TAN increased the expressions of PepT1-related genes and the activities of the intestinal trypsin and chymotrypsin. This conclusion indicates that ammonia nitrogen stress affects the intestinal digestion and absorption performance of aquatic animals, and reducing ammonia nitrogen to a suitable level can improve the protein digestion ability of animals