The effects of using plant ingredients in Senegalese sole (Solea senegalensis) diet on immune competence and intestine morphology and microbial ecology are still controversial. Probiotics or immunostimulants can potentially alter the intestinal microbiota in a way that protects fish against pathogens. The current study aimed to examine the intestine histology and microbiota and humoral innate immune response in juvenile sole fed diets with low (35 %) or high (72 %) content of plant protein (PP) ingredients supplemented with a multispecies probiotic bacteria or autolysed yeast. Fish fed the probiotic diet had lower growth performance. Lysozyme and complement activities were significantly higher in fish fed PP72 diets than in their counterparts fed PP35 diets after 17 and 38 days of feeding. At 2 days of feeding, fish fed unsupplemented PP72 showed larger intestine section area and longer villus than fish fed unsupplemented PP35. At 17 days of feeding, fish fed unsupplemented PP72 showed more goblet cells than the other dietary groups, except the group fed yeast supplemented PP35 diet. High dietary PP level, acutely stimulate fish innate immune defence of the fish after 2 and 17 days of feeding. However, this effect does not occur after 73 days of feeding, suggesting a habituation to dietary treatments and/or immunosuppression, with a reduction in the number of the goblet cells. Fish fed for 38 days with diets supplemented with autolysed yeast showed longer intestinal villus. The predominant bacteria found in sole intestine were Vibrio sp. and dietary probiotic supplementation caused a reduction in Vibrio content, regardless of the PP level.

Microwave processing and pelleting methods were assessed to improve aquafeed quality for sexreversed Nile tilapia. The 2 9 3 experimental feeds were prepared with and without microwave irradiation of ingredients prior to pelleting with either a meat mincer, extruder or steam conditioner followed by a meat mincer. Five feedstuff ingredients, including fish meal, meat and bone meal, soybean meal, broken rice and rice bran, were irradiated separately at optimal times, according to the thirdorder polynomial regression analysis between in vitro digestibility and microwave irradiation times (r = 0.681-0.942, P < 0.001, n = 42). The prepared feeds were studied for chemical compositions and responses in fish growth performance and feed utilization efficiency. The fish (1.57 AE 0.01 g initial weight) were fed ad libitum for 4 months. All proximate chemical compositions of experimental feeds, except protein, were influenced by microwave processing, pelleting methods or their interaction (P < 0.05). There were no significant effects from either parameter on water quality during the fish trial. Fish fed steamed microwave-irradiated feed, mechanically pelleted with a meat mincer, showed the highest growth performance (weight gain 18.91 AE 0.73 g and specific growth rate 2.15 AE 0.26% day À1 ) and feed utilization efficiency (feed conversion ratio 1.31 AE 0.05 g feed g gain À1 and protein efficiency ratio 2.27 AE 0.08 g gain g protein À1 ) compared with the other dietary groups. These findings indicate that microwave irradiation of feed ingredients prior to steam conditioning followed by mincing can improve aquafeed production quality.

Zinc is an essential trace mineral to fish and vital to various biological processes and function. The artificial diets offered to intensively cultivated fish must possess the zinc content required by the animal metabolism for health maintenance and high weight gain. However, essential elements must also be in an available form to be utilized by the organism. Thus, this study was designed to evaluate the effects of different zinc forms, including organic zinc (zinc amino acid complex) and inorganic zinc (zinc sulfate) as feed additives in diets on in vitro protein digestibility, growth performance, feed utilization, digestive enzyme activity, immune response and muscle quality of Asian seabass (Lates calcarifer). The study was assigned in CRD with 3 treatments and 3 replicates. Three groups of fish with mean weight 22.54 ± 0.80 g, were given a basal diet either unsupplemented (control) or supplemented with 50 mg Zn kg −1 , as zinc sulfate (ZnSO 4) or zinc amino acid complex (ZnAA). The fish were fed experimental diets 3.0% of their body weight per day, twice daily at 08.00 and 16.00 h, for 10 weeks. At the end of the experiment, no significant differences were observed on protein digestibility, survival, growth performance and feed utilization across the three dietary treatments (P>0.05). Fish fed ZnSO 4 diets exhibited a significant increase in the specific activities of total protease, pepsin and trypsin compared with ZnAA and the control (P<0.05). Hematocrit, lysozyme and superoxide dismutase activities of fish fed ZnAA diets were significantly higher compared with all other groups (P<0.05). However, no significant differences were observed for muscle quality and whole body composition (P>0.05). The results of the present work allowed us to conclude that there was no difference in the growth between the two zinc sources but ZnAA supplementation exhibited a higher immunity response in Asian seabass.

Probiotic influence on fish immune response and digestive capacity is extensively discussed in aquaculture. In this experiment, a feeding trial was carried out for 100 days to evaluate the cross-effects of probiotic supplementation and rearing temperature (17, 20 and 23°C) in juvenile seabass (Dicentrarchus labrax). The experimental diet was supplemented with a commercial probiotic blend (Biomin AquaStar Growout) at 3 g/kg diet (5.23 × 10 8 CFU/kg diet), and tested against a non-supplemented diet (control).Growth performance and innate immune responses were analysed at 70 and 100 days of feeding, whereas digestive enzyme activities were determined at 100 days of feeding. At the end of the feeding trial, fish were subjected to a handling stress and cumulative mortality was recorded. Digestive enzyme activities were influenced by temperature, with α-amylase and lipase activities peaking at the higher temperature (23°C) and trypsin at the lower temperature (17°C). Immune parameters showed a significant temperature versus feeding duration effect, with complement system (ACH50) and peroxidase peaking at 70 and 100 days of feeding, respectively.Poststress cumulative mortality was higher at the lowest temperature (17°C), especially in fish fed the control diet. In conclusion, water temperature was the main variable affecting the studied parameters, whereas the dietary probiotic supplementation had influence on the chymotrypsin activity and survival rate in seabass reared at 17°C. K E Y W O R D SDicentrarchus labrax, digestive enzymes, innate immune, probiotics, temperature Finally, in this study, we aimed to determine the effects of dietary probiotic supplementation on growth performance (final body weight, feed conversion ratio, daily growth index and protein efficiency ratio), immune system response (ACH50, lysozyme and peroxidase), digestive enzyme activities (α-amylase, lipase, trypsin and chymotrypsin) and stress-caused cumulative mortality, in seabass reared at three temperatures (17, 20 and 23°C) for 100 days. | INTRODUCTION | MATERIALS AND METHODS All | Experimental designThe experimental system was composed of 18 tanks with 80-L capacity each connected to a single recirculation system (TMC | Animals and dietsSeabass juveniles (12.7 ± 0.4 g) were purchased from a hatchery company situated in Gravelines, France. After arrival to the fish rearing facility, seabass were kept in quarantine for 15 days. Then, they were transferred to the experimental recirculation system, individually weighed and equally distributed into 18 tanks (26 fish/ tank) at a density of 3.4 kg/m 3 .The basal diet formulation was used as control diet (Table 1) the duration of the feeding trial, as recommended by the producer.The CFU counts of the diets were performed before and after the trial.Diets were prepared according to the normatives ISO 6887-1:1999, ISO-7218:2007 and ISO 6498:2012 considering the guidelines for microbiological sample preparation of food and animal feeding stuffs.Thereafter, the quantification of bacteria ...

Since Asian sea bass is one of the economically most important fish, aquaculture conditions are constantly optimized. Evidence from feeding studies combined with the current understanding of the importance of zinc for growth and immune defense suggest that zinc supplementation may be a possible approach to optimize aquacultures of Asian sea bass. To investigate the effects of zinc deficiency and zinc supplementation, cells from Asian sea bass were incubated in culture medium with different zinc contents. The expression of genes, important for zinc homeostasis, redox metabolism, and growth hormones was analyzed using RT-PCR. Zinc deficiency induced the expression of certain zinc transporters (ZIP14, ZIP10, ZIP6, ZIP4, ZnT4, ZnT9) as well as of SOD1, IGF I and IGF II, while expression of ZnT1 and metallothionein (MT) was reduced. Zinc supplementation decreased the expression of ZIP10, while expression of ZnT1 and MT were elevated. No differences in the effects of zinc supplementation with zinc sulfate compared to supplementation with zinc amino acid complexes were observed. Thus, extracellular zinc conditions may govern the cellular zinc homeostasis, the redox metabolism and growth hormone expression in cells from Asian sea bass as reported for other fish species. Our data indicate that supplementing aquacultures with zinc may be recommended to avoid detriments of zinc deficiency.