فصلنامه تغذیه آبزیان
سال هفتم شماره 1 (پیاپی 15، بهار 1400)

Caspian brown trout is one of the valuable, commercial, anadromous, and endemic species of the Caspian Sea, which has noteworthy the attention of many scientists. This study was carried out using Caspian brown trout fingerlings (n = 300) with an initial average weight of 42 g for two months. In this study, different amounts of carrot powder (total carotenoids) were added to fish diets including a control group and five treatments i.e. 0 (control), 50 (T1), 100 (T2), 150 (T3), 200 (T4) and 250 mg/kg (T5). The effects of different amounts of carotenoids were investigated on some blood parameters of fingerlings, including lysozyme, alkaline phosphatase, alanine aminotransferase, aminotransferase, glucose, total protein, and cortisol. According to the results, significant differences (p<0.05) were observed in the amounts of serum lysozyme between different treatments. Treatment 2 by an average of 51 ± 3.61 U/mL and control group by 40.67 ± 2.52 U/mL exhibited the highest and lowest levels of the enzyme, respectively. Based on the results, a significant difference (p<0.05) was observed between different levels of cortisol in the treatments, so that the highest and lowest cortisol levels in the control group and treatment 2 with 50 ± 7 and 26.67 ± 4.04 (ng/mL) was observed. In general, based on the results of this study, it was found that different levels of carotenoids in the diet of salmon brown trout can display a significant effect (p<0.05) on blood indices.

To investigate the effects of partial replacement of calf fat and canola oil instead of dietary fish oil on the growth performance and chemical composition of rainbow trout, 250 fish with an average weight of 22.2 ± 0.6 g and a density of 20 fish per 500-liter fiberglass tank were distributed and fed over a 90-day period. Experimental treatments (3 replicates each) were as follows: Treatment 1 (control = T1): adding 100% fish oil to the diet; Treatment 2 (T2): replacement of fish oil with 50% canola oil; Treatment 3 (T3): replacement of fish oil with 50% beef tallow fat; Treatment 4 (T4): replacement of fish oil with 25% beef tallow fat and 25% canola oil. According to the results, the highest rate of weight gain, biomass increase, survival rate and the lowest feed conversion ratio were observed in the control and T4. The lowest percentage of weight gain, specific growth rate, daily growth index and feed, protein and fat efficiency ratios were measured in T3. According to the results, the protein production and fat production values were the highest in T3, exhibiting significant differences with other experimental treatments. The results showed that the amount of moisture in T3 was significantly lower than in the other treatments. In addition, the amounts of fat in T3 and T4 were significantly higher than in the control and T2. The lowest percentage of protein was observed in T2. In conclusion, using a combination of animal fats with vegetable oils and fish oil has a much better effect compared to using each of them alone with fish oil. Therefore, treatment 4 (replacement of fish oil with 25% beef tallow fat and 25% canola oil) is recommended in terms of the studied parameters.

This study was conducted to evaluate the effect of dietary levels of lemon essential oil encapsulated in chitosan nanoparticles on hematological indices and antioxidant status of rainbow trout fry. Accordingly, the fish (4.74 ± 0.14 g in weight) were distributed in 12 fiberglass tanks with 20 fish per tank and were fed with different levels of lemon essential oil loaded in chitosan nanoparticles including control group with no additive (C0%), 0.5% (T0.5%), 0.75% (T0.75%) and 1% (T1%) for 8 weeks in triplicates. The results showed that the highest number of RBC was in T0.75% compared to T0.5% and C0% (p<0.05). The maximum hemoglobin value was observed in T1% and T0.75% compared to the other experimental groups (p<0.05). In addition, in terms of the blood indices, MCH index showed a significant increase in T1% and T0.75% compared to the other treatments. The maximum WBC and lymphocytes were observed in T1% compared to the other experimental groups (p<0.05). Serum antioxidant enzymes showed the highest catalase activity and glutathione peroxidase in T1% compared to the other groups (p<0.05). Furthermore, superoxide dismutase activity elevated significantly only in T1% compared to C0% (p<0.05). However, the oral administration of 0.75% and 1% of lemon peel essential encapsulated with nanochitosan resulted in a significant elevation in the serum malondialdehyde compared to T0.5% and C0% (p<0.05). Overall, the results of this study showed that the addition of lemon essential oil encapsulated in chitosan nanoparticles, especially at 1%, can enhance the hematological indices and antioxidant defense system of rainbow trout.

In this study, the effects of mixture of dietary nano-selenium, vitamin C and E on growth indices, liver enzymes and nonspecific immune response of juvenile Huso huso were investigated. One hundred and twenty individuals juvenile Huso huso with average weight of 77.77 ± 2.3 g were fed with four diets including treatment A (TA by adding 0.1, 30 and 100 mg/kg), treatment B (TB by 0.2, 60 and 200 mg/kg), treatment C (TC by 0.3, 90 and 300 mg/kg) and control group (without adding nano-selenium, vitamin C and E) for 10 weeks. At the end of the rearing period, blood samples were taken from fish to evaluate liver enzymes and immune system indices. No significant differences were observed in growth indices, feed conversion ratio and protein efficiency ratio (p>0.05). The lowest activities of ALT and AST were found in TA and TB (p>0.05). However, IgM and ACH50 levels were significantly higher in TB and TA than in control group, respectively (p<0.05). The results of this study indicated that the addition of a mixture of nano-selenium, vitamin C and E in TA and TB enhanced nonspecific immune system in juvenile Huso huso.

The effects of feeding strategies on cytological and biochemical indices in juvenile Russian sturgeon were studied. For this, 180 Russian sturgeons (77 ± 0.33 g) were stocked in three treatments with 20 fish in each tank and three replicates. Different feeding strategies including starvation, restricted feeding and feeding to satiation were assessed. At the beginning, middle and at the end of experiment, blood samples were collected to assay the blood indices. The results showed that at the end of the experimental period, starvation caused a significant decrease in the number of white blood cells (WBC) and mean corpuscular volume (MCV; p<0.05), while significant elevations were observed in the red blood cell count (RBC), hemoglobin (Hb) and mean corpuscular hemoglobin concentration (MCHC) compared to the other sampling times (p<0.05). The results also showed that there is significant difference between starvation and the other groups in case of WBC, RBC and Hct (p<0.05) after 8 weeks, while no significant differences were found among treatments in terms of Hb, MCV, MCH and MCHC (p>0.05). Moreover, the results exhibited that starvation leads to a significant decrease in the plasma glucose and total protein, while a significant increase in cholesterol and triglycerides compared to the other treatments (p<0.05). This study displayed some adverse effects of starvation on hematological and biochemical indices of Russian sturgeon, so that most of hematological and biochemical indices in starvation were significantly different from the other groups. Therefore, this study indicates that Russian sturgeon is unable to acclimate to long-term starvation period and adverse effects of starvation will increase over time.

To evaluate the effects of dietary flaxseed meal on biochemical parameters and plasma enzymes in Siberian sturgeon Acipenser baerii, 32 individuals, 955.06 ± 53.38 g in average weight were selected and randomly distributed in eight 500-L tanks and fed with different levels of dietary flaxseed meal including 0 (control), 50 (F50), 100 (F100) and 150 (F150) g kg-1 diet for 180 days. Biochemical indices and plasma enzymes were determined on the 30th and 180th days. The fish in control group showed significantly higher glucose and cholesterol levels than the other groups. Flaxseed meal exhibited no significant difference in triglyceride, however, triglyceride reduced in all of the flaxseed meal treatments on the 180th day compared to the 30th day. Calcium, total protein, albumin and globulin levels displayed no significant difference in all treatments, while the albumin:globulin ratio increased in control on 180th day compared to 30th day. Alkaline phosphatase activity decreased in F100 and F150 on 180th day. Aspartate aminotransferase decreased in F150 on 30th day and in all the flaxseed meal treatments on 180th day. The highest and lowest levels of lactate dehydrogenase and alanine aminotransferase activities were found in control and F150 on 180th day, respectively. Results of this study indicate that it is possible to use flaxseed meal in the diet of Siberian sturgeon during the growth period up to 15% without negative effect on plasma enzymes and biochemical parameters.