فصلنامه تغذیه آبزیان
سال پنجم شماره 1 (پیاپی 9، بهار و تابستان 1398)

Effects of diets containing microwave-irradiated canola meal were evaluated on growth, nutrition performance, carcass composition and digestibility of nutrients in Huso huso fry with 31.18 ± 1.43 g in initial weight during 8-week experiment in a factorial design 4 × 2 with 8 treatments, each with 3 replications. Treatments included T1: %20 canola meal without irradiation; T2, T3 and T4: 20% irradiated-canola meal at 800 watts for 5, 10 and 15 min respectively; T5: 40% canola meal without irradiation; T6, T7, and T8: %40 800 watt – radiated canola meal at 5, 10 and 15 min respectively. At the end of the experiment, according to the results, the effects of diet containing microwave-irradiated canola meal on the final weight, weight gain, specific growth factor, feed conversion ratio and daily growth in H. huso fry were significant (p<0.05). The highest final weight, percentage of weight gain, daily growth and specific growth rate were found in T4, while the lowest ones in T5 (p<0.05). Food conversion ratio increased significantly in T5 compared to the other treatments (p<0.05). The results of analysis of variance exhibited that the effects of both canola meal rate (%) and irradiation time and also their interactions caused significant differences in the growth indices except for the coefficient of conversion (p<0.05), but only irradiation time displayed significant effect on food conversion ratio (p <0.05). During the experiment, survival rate was 100%. Microwave-irradiated canola meal diet did not significantly affect the protein and fat contents of the fish carcasses (p>0.05), but showed significant effect on the carcass ash content (p<0.05). According to these results, by increasing irradiation time, the protein digestibility increased (p<0.05). Microwave-irradiated canola meal exhibited no significant effects on fat digestibility and dry matter content (p>0.05). So, it can be added to the diet up to 40% without any unfavorable effect on protein digestibility and growth rate.

Selenium is a trace element important for the normal growth and physiological functions in aquatic animals. In this experiment, its effects on the immune and hematological indices were studied in rainbow trout, Oncorhynchus mykiss (Walbaum, 1792) at different stages for 60 days. The experiment was carried out on 3 life stages (egg, alevin, fry), exposed to 0 (control), 0.5, 1 and 1.5 mg/L selenium nanoparticles each with 3 repetitions once penetrating with sodium hypochlorite. The results exhibited that the highest lysozyme level was observed in the fish exposed to 1 mg/L nano selenium in the alevin stage (p<0.05), while the lowest was reported in the control group. Immunoglobulin levels in the alevin stage at 1 and 1.5 mg/L nanoparticles were significantly higher than the control group and also than the other experimental treatments (p<0.05). The highest numbers of white blood cells were found at treatments exposed to 1.5 and 1 mg/L in the alevin stage, while the cell number in the control group was significantly lower than in the other treatments (p<0.05). Besides, the numbers of red blood cells in all treatments during the alevin stage were significantly higher than in the control group (p<0.05). The highest hemoglobin and hematocrit levels were observed in the treatments during alevin stage, while the lowest levels were found in the control group, such that the differences were significant (p<0.05). In total, exposing to 1 mg/L selenium nanoparticles in the alevin stage is the best concentration during the exact life time for rainbow trout growth and development.

This study was carried out to evaluate the effects of adding molasses (in water and diet) on growth performance, digestive enzyme activity and non-specific immunity of Cyprinus carpio in a biofloc system. Common carp (12.06± 0.35 g mean initial weight) were cultured in 3 treatments with triplicate for 7 weeks with daily addition of sugar beet molasses as carbon source to maintain the C/N ratio (1:15) which included: addition molasses to water (MW) and feed (MF) in biofloc system and clean water control without molasses addition (control). There was no statistically significant difference in water quality (ammonia and nitrate) between different experimental treatments. The growth and feed performance were significantly higher in the receiving molasses treatment than the control (P<0.05). The digestive enzymes of amylase, lipase and protease had a significant statistical difference between experimental treatments (P<0.05). Protease activity was significantly higher in MW and MF treatments than control. Plasma immunoglobulin and lysozyme levels of fish cultured were significantly higher in the biofloc system (MW and MF) than in the control, whereas plasma cortisol was significantly lower in receiving molasses treatment. Overall, the present findings suggested that molasses can be taken into account as functional feed additives for Cyprinus carpio.

The present study was conducted to evaluate the effect of probiotic bacteria Pediocucus acidilactici encapsulated with alginate and resistant starch (Hi maize) coated by chitosan, on growth indices, intestinal flora and carcass composition of rainbow trout (Oncorhynchus mykiss). Rainbow trout fingerling with an average weight of 18.41 ± 0.32 g were fed with diets including: encapsulated probiotic, free probiotic, diet containing capsules free of bacteria (positive control) and control diet containing no probiotics for 60 days. The results exhibited that there were no significant differences in growth rate, weight gain, specific growth rate and feed conversion ratio in different groups. The highest number of lactic acid bacteria was found in the fish received the encapsulated bacteria while the lowest was in the control group (p<0.05). Maximum carcass protein and fat contents were observed in encapsulated bacteria treatment and maximum carcass ash was in control group (p<0.05). Totally, the results suggest that encapsulated P. acidilactici improves the growth performance, body composition and bacterial flora of rainbow trout.

The present study was conducted to evaluate the effects of different levels of dietary protein and lipid on the expression of genes involved in immunity (lysozyme and TNF- 1α) and appetite (Ghrelin) in zebrafish, Danio rerio. So that, 9 diets with 3 protein levels (25, 30 and 35%) and 3 lipid levels (4, 8 and 12%) were prepared. One hundred and thirty five fish, 5 in each group, with an average weight of 1.23 ± 0.02 (g) were randomly distributed into 27 aquaria (20-liter) and fed 3 times daily during 4 months. A factorial experimental design was used for this study. The results revealed that the growth parameters (final weight, body weight gain, body weight gain percentage, specific growth rate and feed conversion ratio) and expression of immune and appetite genes increased significantly by increasing dietary protein levels in the treatment fed with 35% protein (p<0.05(. Increasing dietary lipid increased lysozyme expression and growth indices in fish fed with 12% lipid compared to other treatments; increased ghrelin gene expression in 12% compared to 4% significantly (p<0.05) and also insignificant increased TNF-1α expression (p>0.05). The combined effects of protein and lipid increased the lysozyme, TNF- 1α and ghrelin gene expression (p<0.05). The highest gene expression among all genes was observed in the diets containing 35% protein and 12% lipid. These findings revealed that dietary protein and lipid can enhance the function of immune system and appetite in zebrafish.

In this study, replacement of carrot powder with synthetic astaxanthin (SA) in the rainbow trout diet was examined by some growth parameters (final weight, specific growth rate, condition factor, protein efficiency ratio (FCR), food conversion ratio and daily food intake) and blood indices (cortisol, glucose, total protein, alkaline phosphatase, alanine aminotransferase, asparate aminotransferase and lysozyme). For this purpose, 6 diets including control (no replacement), diet with 100% astaxanthin (at 100 mg/kg of diet) and four diets with partial and total replacement of SA by carrot powder (25, 50, 75 and 100%) were prepared. Growth performance indicated that replacement of SA by carrot powder caused effect on the weight gain and specific growth rate (p<0.05). With the increase of carrot powder in the fish diet, weight gain increased and FCR more reduced. The best results were obtained in the treatment that carrot powder replaced over 75% in the diet. Therefore, replacement of SA with carrot powder is fully possible in the rainbow trout diet.

The Siberian sturgeon is a suitable species for using in aquaculture industry. The purpose of this study was to investigate the effect of glutamine on intestinal digestive enzymes and histological structure of intestine in Siberian sturgeon and to determine the optimal amount of glutamine in rearing conditions. This study was performed on 126 fish with a mean weight of 45.71 ± 7.56 g in six treatments (control, 5, 10, 15, 20 and 30 g glutamine /kg feed) and three replicates during 8 weeks in Shahid Dr. Beheshti Sturgeon Restoration and Genetic Conservation Center in Sangar, Rasht. Fish intestine was prepared for study the digestive enzymes activity and Arabic gum-olive oil emulsion, azocasein 2.5% and starch were used as substrate to measure lipase, protease and amylase enzymes, respectively. For examination of villus length and intestinal epithelium, 1 cm of intestinal tissue was fixed in Bouin's solution. The samples were then dehydrated, clarified, paraffin-embedded and molded. After sectioning tissue, staining was performed by eosin-hematoxylin method. The results showed that amylase, protease and lipase were significantly different between treatments (p<0.05). The highest amount of amylase and lipase levels was observed in treatment of 30 g glutamine and the highest amount of protease was in treatment of 20 g glutamine. Also, the size of intestinal villi length and intestinal epithelium were significantly different among treatments (p<0.05). The highest intestinal villi length was observed in treatment of 20 g glutamine and the highest intestinal epithelium was seen in treatment of 30 g glutamine. Because of the highest secretion of amylase, protease and lipase enzymes and the highest villus length and intestinal epithelium in treatments of 20 and 30 g glutamine, these levels could have a positive effect on the structure of intestinal physiology and the digestive enzymes in this fish.

This study was designed to investigate the effects of different levels of betaine including zero (control), 0.5, 1 and 2% on growth performance and carcass chemical composition of Stellate sturgeon (Acipenser stellatus) fingerlings. Experiment was performed with 4 treatments with 3 replications. One hundred and eighty Stellate sturgeon fingerlings with an average weight of 32 ± 4 g )± standard deviation( were randomly fed in 12 fiberglass tanks (500 L capacity) for 60 days. Fish were hand-fed based on appetite 3 times per day. Diets were used in this experiment contained different levels of betaine concentration 0 (control), 0.5, 1 and 2%. The results showed that there was no significant difference between different treatments on weight gain, specific growth rate, condition factor and feed conversion ratio )p>0.05(, but different levels of betaine resulted significant differenc on body compositions (p<0.05). The body protein in 2% betaine showed significant increase in comparsion with control. The body lipid in 2% betaine showed significant decrease in comparsion with control and treatment that was fed with 0.5% betaine. The body moisture in 2% betaine and treatment that was fed with 1% betaine showed decrease in comparsion with control treatment. There was no significant difference in body ash in different treatments. The present study reveals that the use of betaine, although not having a significant positive effect on growth performance, but would improve the carcass chemical composition in the Stellate sturgeon.

This study aimed to evaluate the effects of different levels of microencapsulated antioxidant supplementation (Nano-selenium, Vitamins E and C) on growth performance, body composition and some blood biochemical indices in rainbow trout, Oncorhynchus</em> mykiss</em>. Fish with an average weight of 9.07 ± 0.36 g were distributed into 12 tanks and divided into four experimental groups: treatment 1 (N-Se; 0.1, E; 30 and C; 100 mg/kg), treatment 2 (N-Se; 0.2, E; 60 and C; 200 mg/kg), treatment 3 (N-Se; 0.3, E; 90 and C; 300 mg/kg) and commercial diet as control. The results exhibited that the fish fed with diets containing additional microencapsulated antioxidant supplementation induced higher final growth, weight gain, the protein and lipid efficiency ratios, while had no different in feed conversion ratio. The body composition such as protein and lipid did not exhibit significant differences between the treatments. The serum lysozyme activity and superoxide dismutase enzyme were significantly elevated in fish fed with supplemented diet compared to the control. The alanine aminotransferase and alkaline phosphatase significantly increased in the three treatments whereas aspartate aminotransferase reduced in fish fed with antioxidant supplementation compared to the control. The present results indicated the beneficent effects of microencapsulated Nano Se and vitamins E and C on growth rate and immune response in rainbow trout.

In recent years, the use of dietary supplements, especially synbiotics, in the diet of farmed fish has been considered due to its beneficial effects on fish health. In this study, the effects of different levels of symbiotic Biomin Imbo were examined on the antioxidant activities, digestive and bacterial flora in the intestine of Mugil cephalus</em>. One hundred and twenty grey mullet with a mean weight of 3.92 ± 0.43 g were reared in 60-liter aquaria for 60 days (10 fish in each aquarium) and the treatments were fed with diet containing symbiotic supplement at different levels including 0.5 (T0.5</sub>) , 1 (T1</sub>), 1.5 g (T1.5</sub>) synbiotic per kg of feed, while control contained no supplementation. Feeding was carried out manually. At the end of the experiment, the fish intestine was removed and antioxidant enzyme activities including superoxide dismutase, glutathione peroxidase and glutathione S-transferase as well as digestive enzyme levels including lipase, amylase, alkaline phosphatase, protease, pepsin, chymotrypsin along with microbial flora were assayed. According to the results, superoxide dismutase activity at T1</sub> and T1.5</sub> and glutathione S-transferase and glutathione reductase at T1</sub> were significantly increased compared to the control (p<0.05), whereas glutathione peroxidase activity did not exhibit any significant difference (p>0.05). The high levels of synbiotic displayed significant effects on all the digestive enzyme activities except for alkaline phosphatase and lipase (p<0.05). Total number of viable and lactic acid bacteria in T1</sub> and T1.5</sub> significantly increased compared to the control, while the number of coliforms in these treatments was significantly decreased (p<0.05). The findings of the present study exhibited that the diet containing 1 g synbiotic per kg of feed can be used as a suitable dietary supplement for grey mullet.

This study was conducted to assess the ontogeny of the olfactory and taste organs in Caspian Kutum, Rutilus kutum</em>, from hatching up to 23 days post hatching (DPH). So that, the larvae were randomly sampled daily from 1 to 23 DPH. After fixation in buffered formalin and glutaraldehyde, the histological sections were prepared, then the olfactory and taste organs were examined using light and electron microscopies. The results exhibited complete nasal formation and the increasing number and size of the taste buds in the oral cavity, lips, as well as around the mouth on 5 DPH. In addition, on 12 DPH, further development of the olfactory cells and taste buds were observed. This increasing trend was continued until 16 DPH. According to the results, the olfactory organ was completed earlier than the taste one, and the number of taste buds was higher on the upper lip. The maturation of the taste buds was observed at 20 DPH. The results revealed that the development of chemical sense organs is closely related to the development of Caspian Kutum’s gastrointestinal system.

Probiotic and prebiotic have many advantages and are employed as a method for aquaculture yield improvement. The main goal of the current study is to evaluate the effect of dietary Lactococcus</em> lactis </em>subsp. lactis</em> as well as chitin on growth performance, carcass composition and feed digestibility in common carp, Cyprinus carpio</em>. So that, 360 juvenile carps with mean initial weight of 12 ± 1.5 g were randomly distributed in 6 treatments based on adding different chitin levels including 0, 1, and 2% and probiotic including 0 and 2% (1×107</sup> CFU/g) to a basal diet and cultured for 8 weeks. At the end of the experiment, growth indices, survival rate, carcass composition and nutrient digestibility were measured. Maximum final weight, weight gain, feed conversion ratio, daily growth rate, feed efficiency and condition factor as well as the lowest FCR were observed in treatments fed with probiotic 2%, chitin 1% and probiotic 2% + chitin 1% (P<0.05). Dietary chitin and probiotic did not alter feed intake and total length in common carps (P>0.05). The experimental treatments did not influence the carcass composition and nutrient digestibility. In conclusion, it seems that adding 2% probiotic and 1% chitin can improve some growth indices in common carp, but can not affect carcass composition and nutrient digestibilty.