فصلنامه تغذیه آبزیان
سال هفتم شماره 4 (پیاپی 18، زمستان 1400)

Considering the global consumption of frogs and providing 95% of frogs' legs at the international level through fishing from the natural environment, environmental concerns have been given more attention. Therefore, with the aim of developing the artificial reproduction of frog, the effects of using different dietary- animal and plant proteins on metamorphism of frog (Rana ridibunda) were investigated. The experimental diets were: (i) a diet containing 100% animal protein, (ii) a diet containing 100% plant protein, (iii) a diet containing 50% plant and 50% animal proteins, (iv) a diet containing 30% plant and 70% animal proteins, and (v) a diet containing 70% plant and 30% animal proteins. The tadpole fed the experimental diets in a 90-day period. The individual weight was significantly different among the treatments during the experimental period (p<0.05). The highest weight loss occurred in the 10th week of rearing in the 3, 3 and 1 treatments, respectively. Maximum weight loss was observed in the treatment 5 in the 12 week and in the treatment 2 in the week 13. Given the individual weight, and also the metamorphism process and biomass of froglets, the diet containing 50% plant and 50% animal proteins nominated more capable diet for production of froglets (Rana ridibunda).

One of the most common methods of preserving fish worldwide, especially in coastal areas is sun-drying. In order to determine the quality of dried anchovy (Encrasicholina punctifer), 40 samples of dried fish by the traditional method and in sunlight were collected from the Qeshm Island. In the laboratory, proximate compositions, chemical quality indicators, and microbial quality were measured. The amounts of protein, fat, fiber, ash and moisture were 58.10, 6.11, 0.59, 18.69 and 16.02% based on a dry weight basis, respectively.  The peroxide value (PV) was 0.3 mEq O2/kg which was lower than the acceptable limit, while the total volatile basic nitrogen (TVBN) was 243.36 mg/100 g beyond the limit. Total viable counts (TVC) were 2.8 × 103 CFU/g was lower than the acceptable limit, while yeast and mold count (6.06 × 102 CFU/g) beyond the limit. Contaminations of dried anchovy by Escherichia coli, Staphylococcus aureus, coliform, Clostridium perfringens and reducing bacteria (Clostridiums) were positive. The most frequent prevalence was related to S. aureus by 52.17% and E. coli by 39.13%. In general, the dried anchovy exhibited a high protein and fat content, but low chemical quality. The bacterial spoilage was not occurred, but it was susceptible to spoilage by molds and yeasts. Maintaining quality of crude fish before drying, improving the quality of location and the method of drying process can decline the secondary contamination of the dried fish samples by pathogenic bacteria, leading to improve this high valuable nutritional product.

In this study, the effects of culture medium and oil enrichment on the growth and approximate analysis of microworm, Panagrellus redivivus were investigated. Three main ingredients (oat, potato, and wheat) and their mix in equal proportion, and two types of vegetable oil (sunflower and sesame) were used as cultivation medium. Therefore, 12 treatments in 6 replications including 4 culture mediums without oil, with sunflower oil, and with sesame oil were used. Oil was used as 3.4% of the total weight of the culture medium. After 12 to 14 days, harvesting was performed. Production and approximate analysis of microworms were recorded. The results showed that the amount of microworm production was the highest in mixed, potato, oat, and wheat treatments, respectively. Also, using oil exhibited a significant effect on the microworm fat and increased the total fat of the worm. The highest amount of oil was observed in the mixed-sunflower treatment, while the lowest in the wheat treatment without oil (p<0.05). On the other hand, by elevating in oil, the protein rate decreased (p<0.05). The type of culture medium displayed a significant effect on all measured amino acids except cysteine. However, the oil added to the culture medium only revealed a significant effect on some amino acids, i.e., arginine and tryptophan (p<0.05). In general, the composition of the culture medium and the addition of oil displayed a significant effect on the production and body composition of microworm exhibited that this nematode has a high enrichment capability.

This study evaluated the effect of different levels of dietary rainbow trout by-product protein hydrolysate on hematological, immunological and biochemical serum parameters and antioxidant enzymes of juvenile Siberian sturgeon (Acipenser baerii). For this purpose, 300 fish with an average weight of 67 ± 3 g were distributed in 12 tanks and were fed for 56 days with different levels of by-product protein hydrolysate (PH) in 4 treatments including 0 (control), 5g (5PH), 10g (10PH) and 20g (20PH per kg of feed. The highest white blood cell count and hematocrit percentage were observed in the treatments of 10PH and 20PH which was significantly different from those fed with 5PH and control (p<0.05). The highest amount of the serum glucose and the lowest amount of triglyceride were obtained in 10PH and 20PH. Fish fed 10PH and 20PH exhibited lower levels of AST and ALP enzymes than the control group (p<0.05). Evaluation of serum immune indices showed that there was a significant difference in IgM, C3, ACH50 and serum respiratory burst activity of fish fed 10PH compared to other treatments (p<0.05). Also, lysozyme activity, total protein content, complement component C4 in fish fed with 10PH and 20PH displayed a significant difference with 5PH and control group (p<0.05). In this study, serum superoxide dismutase and catalase indices in 10PH and 20PH revealed a significant difference with other treatments (p<0.05), in addition to the activity of the glutathione peroxidase (p<0.05). Overall, effects of PH, especially 10PH on the examined indices in Siberian Sturgeon were positive and significant.

The present study was performed to examine the effects of probiotic addition to diet containing soybean meal (SBM) on growth and intestinal histomorphometry of rainbow trout. A total of 300 fry with mean initial weight of 20.05 ± 0.20 g were distributed to 12 tanks for 90 days. Experimental diets were included control (SBM 0 + probiotic 0), SBM 0 + probiotic 1, SBM 20% + probiotic 0, SBM 20% + probiotic 1, SBM 40% + probiotic 0 and SBM 40% + probiotic 1. On the 30th day, the highest body weight increasing rate (BWI %) and specific growth rate (SGR) were observed in diet containing SBM 0 (0 and probiotic 1) and SBM 20% + probiotic. On the 60th day, adding probiotic to SBM 0 and SBM 20% led to the highest BWI (p < 0.05). The lowest values of final weight, BWI (%) and SGR were achieved in SBM 40% without probiotic (p<0.05). Feed efficiency ratio was elevated in diets containing SBM 40% (p<0.05). On the 90th day, final weight, final length and SGR were highest in fish fed SBM 0 (0 and 1 probiotic) and SBM 20% containing probiotic (p<0.05). According to intestinal histomorphometry, on the 60th day, the highest villus height was found by supplementation of probiotic to SBM 0 (p<0.05). Epithelium thickness was significantly reduced by increasing SBM level to 40% (p<0.05). The greatest mucous thickness and goblet cells were observed  in SBM 0 (0 and 1 probiotic) and SBM 20% containing probiotic groups (p<0.05). According to results on the 90th day, villus height was significantly decreased by SBM level increasing (p<0.05). Epithelium thickness, mucous thickness and goblet cell in diet containing SBM 40% were lower than those in the other treatments (p<0.05). Considering present study, addition of probiotic to SBM 20% is beneficent to improve growth rate and intestinal histology.

The study was designed to evaluate the effects of spirulina algae and the acidifying impacts of citric acid on the variation of hematological and immune indices in common carp, Cyprinus carpio. The study was completely random in design with nine treatments, 3 replicates and the control, which included using basic diet without any additives. The treatments included T1: basic diet supplemented with 0.5% citric acid; T2: basic diet supplemented with 0.1% citric acid; T3: basic diet supplemented with 0.2% spirulina extract; T4: basic diet supplemented with 0.3% spirulina extract; T5: basic diet supplemented with 0.2% spirulina extract and 0.05% citric acid; T6: basic diet supplemented with 0.3% spirulina extract and 0.01% citric acid; T7: basic diet supplemented with 0.2% spirulina extract and 0.01% citric acid; and T8: basic diet supplemented with 0.3% spirulina extract and 0.05% citric acid. For this purpose, 270 juvenile carp fish (mean weight: 11.35 ± 1.21 g) were fed with the experimental diets for 8 weeks. At the end of the trials, the number of white blood cells (WBCs), red blood cells (RBCs), Hb, HCT, differential white cells (lymphocyte, eosinophil, neutrophil and monocytes) were measured. The mean volume of red blood cells (MHC), mean concentration of cellular hemoglobin (MEHC) and immune indices of fish blood including Lysozyme, GM, and immunoglobulin were also measured. The results indicated significant differences in certain blood factors (i.e., HCT, neutrophil and lymphocyte) between experimental diet groups and the control (p < 0.05). In addition, certain immune indices in the experimental groups were at healthier levels than those in the control (p < 0.05). Finally, the study showed that spirulina algae combined with citric acid acidifier could enhance the body immune system of juvenile carp fish.