Chicken Meal as a Fishmeal Substitute: Effects on Growth, Antioxidants, and Digestive Enzymes in Lithobates catesbeianus.

In pursuit of sustainable aquaculture, this study was performed to evaluate chicken meal as a substitute for fishmeal in bullfrog diets. Three experimental groups were established: a control group (FM) with 20% fishmeal, a CM50 group with 50% replacement (10% fishmeal), and a CM100 group with 100% replacement (0 fishmeal). Bullfrogs were fed for 56 days. The CM50 group exhibited significant increases in total weight gain and survival rate and a notable decrease in feed coefficient (p < 0.05). However, the CM100 group showed contrary effects. Increasing chicken meal substitution correlated with decreased amino acid content in muscle. Notably, the CM50 group demonstrated enhanced activities of antioxidant enzymes (CAT, T-AOC) and elevated gene expression levels (cat, sod, gst, etc.) in muscle and the intestine (p < 0.05), improved intestinal morphology, enhanced digestive enzyme activities (amylase, lipase), and reduced expression of inflammatory factors (il-1ß, il-8, il-17, etc.). Conversely, the CM100 group's indicators regressed to levels similar to or worse than those of the FM group. Therefore, a 50% substitution of fishmeal with chicken meal effectively promoted bullfrog survival, protected the intestines, and enhanced antioxidant capacity, supporting its potential as a fishmeal alternative. However, the adverse outcomes of the CM100 strategy, including growth retardation and reduced amino acid content in muscle, indicate that complete replacement is unsuitable.

Effect of dietary replacement of fish meal by poultry by-product meal on the growth performance, immunity, and intestinal health of juvenile red swamp crayfish, procambarus clarkia.

The present study was conducted to investigate the dietary replacement of fish meal with poultry by-product meal (PBM) on the growth performance, immunity, antioxidant properties, and intestinal health of red swamp crayfish (Procambarus clarkia). A diet containing 20% fish meal (FM) and complex plant ingredients as the main protein resources was set as the FM group (crude protein 32%, crude lipid 6%). Four diets replacing 25%, 50%, 75%, and 100% fish meal of the FM diet with PBM were set as the PBM25, PBM50, PBM75, and PBM100 groups, respectively. Compared to the FM group, the PBM100 diet significantly decreased growth performance and feed utilization of crayfish, while markedly increasing the activity of serum aspartate aminotransferase. The immune response was depressed in crayfish fed the PBM100 diet as the activities of serum lysozyme and phenoloxidase, gene expression of anti-lipopolysaccharide factors (alf), cyclophilin A (cypa), crustin, and hemocyanin-1 (hep-1) in hepatopancreas were remarkably decreased. The activities of antioxidases and expression of antioxidant-relevant genes in the hepatopancreas were not influenced by PBM inclusion. Crayfish fed different diets exhibited no obvious symptoms of enteritis, but the PBM100 diet destructed intestinal morphology by significantly decreasing the average length of longitudinal ridges. The α-diversity and overall community structure were not significantly influenced but variations were found in the relative abundance of some genera by PBM inclusion. In summary, CAP could successfully replace 75% dietary FM in a basal diet containing 20% fish meal, while higher CAP level compromised growth performance, immunity, and intestinal histology of crayfish.

Exposure to waterborne cadmium induce oxidative stress, autophagy and mitochondrial dysfunction in the liver of Procypris merus.

The present study was performed to determine the effect of waterborne cadmium (Cd) exposure on oxidative stress, autophagy and mitochondrial dysfunction, and to explore the mechanism of Cd-induced liver damage in freshwater teleost Procypris merus. To this end, P. merus were exposed to waterborne 0, 0.25 and 0.5 mg/L Cd for 30 days (equal to 0, 2.22 and 4.45 µmol Cd/l). The waterborne Cd exposure significantly increased hepatic Cd accumulation and impaired histological structure of the liver of P. merus. both low and high-dose waterborne Cd exposure induced oxidative stress in the liver of P. merus, through increases Malondialdehyde (MDA) and reactive oxide species (ROS) accumulation in the liver. The Cd-induced oxidative stress in liver may result from reduction of enzyme activities (superoxide dismutases (SOD), catalases (CAT), GSH-S-transferases (GST)) and transcriptional expression of antioxidant related genes (gpx1, gpx2, cata, gsta1, sod1). Furthermore, the present study showed that waterborne Cd exposure decreased the transcriptional factor (nrf2) expression, which might lead to the down-regulation of antioxidant gene expression. Transmission electron microscopy (TEM) observations demonstrated that waterborne Cd exposure induced autophagy in the liver of P. merus. Gene expression analysis showed that waterborne Cd exposure also induced mRNA expression of a set of genes (beclin1, ulk1, atg5, lc3a, atg4b, atg9a, and p62) involved in the autophagy process, indicating that the influence of Cd on autophagy involved transcription regulation of autophagy gene expression. Waterborne Cd exposure induced a sharp decrease in ATP content in the liver of P. merus. In addition, the expression of mitochondrial function genes (sdha, cox4i1, cox1, atp5f1, and mt-cyb) are significantly decreased in the liver of P. merus in Cd treated groups, manifesting the suppression of Cd on mitochondrial energy metabolism. Taken together, our experiments demonstrate that waterborne Cd exposure induced oxidative stress, autophagy and mitochondrial dysfunction in the liver of P. merus. These results may contribute to the understanding of mechanisms that hepatotoxicity of Cd in teleost.

Re-description of the gudgeon species Saurogobio gracilicaudatus Yao & Yang in Luo, Yue & Chen, 1977 (Teleostei: Cyprinidae) from the Chang-Jiang basin, South China, with a note on its generic classification.

Saurogobio gracilicaudatus, originally described from the middle Yangtze River (Chang-Jiang in Chinese) basin at Yichang and Guanghua (now Laohekou), Hubei Province, South China, is here re-described, with particular concern for oromandibular structures in the mouth. It is uniquely distinguishable from all other species of Saurogobio in having a rostral cap with a slightly crenulated median portion, lips covered with brush-like, conical papillae, and a lower lip with a small, smooth and protruded central pad anteriorly free and posteriorly confluent with lateral lobes. The generic classification of this species is also discussed on the basis of oromandibular structures, which are of taxonomic importance in generic classification of gudgeons.