Effects of antimicrobial peptides on growth,morphology of foregut villi and related genes mRNA expression in the common carp (Cyprinus carpio)

A 60‐day feeding trial was conducted to examine the effects of different levels (0, 100, 200, 400 and 600 mg/kg) of antimicrobial peptides on growth, protease activity of foregut, the morphology of foregut villi and related genes mRNA expression level in the common carp (Cyprinus carpio). The results showed that the feed of antimicrobial peptides promote common carp growth, and the optimal dosage of antimicrobial peptides is 200–333 mg/kg in the common carp feed. The protease activity of 200 and 400 mg/kg groups were significantly higher than the control and other groups (p < 0.05). The foregut villus height with 100, 200 and 400 mg/kg antimicrobial peptide groups were significantly higher than control group (p < 0.05). The crypt depth of 200 and 400 mg/kg antimicrobial peptide groups were significantly lower than control group (p < 0.05). The ratio of villus height and crypt depth of 100, 200 and 400 mg/kg antimicrobial peptide groups were significantly higher than control group (p < 0.05). The ratio with 600 mg/kg group was significantly lower than the control group (p < 0.05). The IGF‐I gene expression level of 200 mg/kg and 400 mg/kg groups were significantly higher than the control group and 600 mg/kg group (p < 0.05). The IL‐1β gene expression level of 100 mg/kg and 200 mg/kg groups were significantly higher than the control group (p < 0.05). These results indicated up‐regulation of growth and immune related genes in antimicrobial peptides fed common carp. Correlation analysis showed that IGF‐I mRNA and IL‐1β mRNA were positively correlated with SGR. IL‐1β mRNA and FCR were significantly negative correlated. It indicated that growth and immune gene common regulated the growth of the carp under antimicrobial peptides intervention. In conclusion, antimicrobial peptides can improve growth and related genes mRNA expression in the common carp. Further studies using molecular biological technique or immunologic methods are required to conclude that antimicrobial peptides are beneficial in common carp.     

Cellular and humoral immune responses of Senegalese sole,Solea senegalensis (Kaup), following challenge with two Photobacterium damselae subsp. piscicida strains from different geographical origins

The present study aimed to investigate leucocyte responses to inflammation as well as some innate immune parameters of Senegalese sole, Solea senegalensis, following challenge with two strains of Photobacterium damselae subsp. piscicida belonging to the European and Japanese clones described for this bacterium. Pathogenicity assays were performed to assess the virulence of each Photobacterium damselae subsp. piscicida strain for sole. Subsequently, fish were intraperitoneally injected with phosphate‐buffered saline (control) or two concentrations (2 × 10² and 2 × 10⁶ CFU mL^?1) of each bacterial strain and sampled after 6 and 24 h. Results showed that the European isolate induces a higher degree of response than the Japanese strain. While blood neutrophilia and monocytosis correlated well with the increase in neutrophil and macrophage numbers in the peritoneal cavity, fish infected with the European isolate presented higher peritoneal cell numbers than fish challenged with the Japanese strain. In addition, alternative complement pathway activity and respiratory burst of head kidney leucocytes increased significantly in fish infected with the European isolate. The enhanced innate immune response displayed by Senegalese sole challenged with the European isolate is probably due to the higher degree of virulence presented by this Photobacterium damselae subsp. piscicida strain.     

Effects of dietary carbohydrate/lipid ratios on growth performance,body composition and glucose metabolism of fingerling blunt snout bream Megalobrama amblycephala

This study aimed to investigate the optimum dietary carbohydrate/lipid (CHO/L) ratio for fingerling blunt snout bream Megalobrama amblycephala (average initial weight: 6.61 ± 0.03 g). Six isonitrogenous and isoenergetic diets were formulated to contain various CHO/L ratios ranging from 1.62 to 24.20. Each diet was tested in four replicates for 10 weeks. Specific growth rate (SGR), feed conversion ratio and nitrogen and energy retention all improved significantly (P < 0.05) as dietary CHO/L ratios decreased from 24.20 to 5.64 but showed little difference (P > 0.05) as dietary CHO/L ratios ranged from 2.45 to 5.64. Hepatosomatic index increased significantly (P < 0.05) as dietary CHO/L ratios increased, whereas intraperitoneal fat ratio showed an opposite trend (P < 0.05). Opposite to moisture content, lipid content of whole body and carcass all increased significantly (P < 0.05) as dietary CHO/L ratios decreased. Liver lipid content showed little difference (P > 0.05) among all the treatments, while liver glycogen content increased significantly (P < 0.05) with increasing CHO/L ratios. High dietary carbohydrate enhanced the activities of liver hexokinase, pyruvate kinase and glucose‐6‐phosphate dehydrogenase but did not induce hyperglycaemia. Based on the second‐order polynomial regression analysis of SGR, the optimal dietary carbohydrate and lipid contents for fingerling blunt snout bream were 291.7 and 81.4 g kg⁻¹, respectively, with a corresponding dietary CHO/L ratio of 3.58.     

Tail Muscle Free Amino Acid Concentration of Pacific White Shrimp,Litopenaeus vannamei,Fed Diets Containing Protein‐bound versus Crystalline Amino Acids

Tail muscle tissue free amino acids (FAA) concentration is reported for subadult (4.3 g) Litopenaeus vannamei fed diets containing only protein‐bound amino acids, crystalline lysine as a supplement to protein‐bound lysine, and only crystalline amino acids (CAA). FAA were determined in shrimp at 0.00, 0.25, 0.5, 1, 2, 4, and 8 h postfeeding. Highest total tissue concentrations of essential amino acids and individual amino acids were typically observed 4 h postfeeding for shrimp fed intact and crystalline lysine‐supplemented feeds. Those shrimp offered diets containing only CAA showed no tissue maxima. Similar uptake patterns for lysine shown by shrimp fed the intact and crystalline lysine‐supplemented diet indicate the potential use of small amounts of crystalline lysine in shrimp feeds.     

Effect of Stocking Density on the Growth,Survival, and Behavior of Postpuerulus Western Rock Lobster,Panulirus cygnus (George) (Decapoda: Palinuridae)

The effect of four stocking densities (30, 60, 100, and 150 lobsters/m²) on the growth and survival of Panulirus cygnus postpueruli was determined over a 112‐d grow‐out trial. Agonistic behavior at each experimental density was recorded using infrared filming. Survival and growth decreased with increasing density, although this trend was only significant between the lowest (30/m²) and the highest densities (150/m²) (P < 0.05) at the conclusion of the grow‐out trial. Density had no significant effect on apparent feed intake but significantly affected food conversion ratios (FCR) across all four densities, with FCR being best at 30/m² and worst at 150/m². The number and frequency of agonistic encounters per tank differed significantly with density, with agonistic encounters being highest at 150/m² and lowest at 30/m². Agonistic encounters coincided with the crepuscular foraging pattern of postpueruli. The reduction in survival and growth of postpueruli at the highest density (150/m²) can be attributed to the significant increase in the number of agonistic encounters. This study supports that P. cygnus postpueruli should be stocked at densities less than 100/m² in order to minimize the negative effect of density on growth and survival.