فصلنامه تغذیه آبزیان
سال هفتم شماره 3 (پیاپی 17، پاییز 1400)

An investigation was carried out to find the effects of different Smizyme phytase levels on growth indices, body composition and nutrient digestibility of farmed Siberian sturgeon, Acipenser baerii. One hundred and eighty fish (average weight 1.19 ± 0.017 kg) were distributed in nine concrete tanks (20 fish in each tank; area = 4 m2; depth = 80 cm) and divided to 3 treatments (F0, F1000 and F2000). Fish were fed for 62 days. Results showed that physaem addition in 2000 IU (F2000) to sturgeon commercial diet (38% protein and 12.5% crude fat) leads to significant increase in final weight, daily growth rate, specific growth rate and the decreased feed conversion ratio compared to the other two groups (p<0.05). Significant raises in protein and dry matter digestibility were observed in the enzyme-fed fish compared to control diet (p<0.05). However, no significant difference in fat digestibility was observed between experimental treatments (p>0.05). Body protein was declined in F1000 and F2000, while body lipid was elevated in F2000 (p<0.05). The highest body carbohydrates was observed in F1000 (p<0.05), while no significant difference was observed in the fish body moisture fed with different diets (p>0.05). Based on the results obtained from growth indices and digestibility coefficient, we suggest adding 2000 IU/kg Smizyme phytase in the fish diet.

This study aimed to investigate the effects of casein blood substitute feed on the growth, survival and reproduction of Hirudo orientalis. At first, 100 leeches with an average weight of 3 g were reproduced. The growth indices of 200 leeches (with an initial weight of 0.038 ± 0.012 g) were measured during 10 months and also reproductive characteristics of 50 leeches during the 8th to 10th months. Leeches were fed at 30-day intervals under two treatments: using fresh blood (T1) or blood substitute feed (T2). During the rearing period, the growth of blood-fed leeches (T1) was significantly (p<0.05) faster than the blood substitutes-fed group (T2). In the 10th month, the two groups exhibited an 18% weight difference with each other. Although the amount of weight, length, diameter and number of cocoons produced in T1 were higher than T2, however the differences were not statistically significant (p<0.05). Survival rate was higher in T1 during growth and reproduction. Fertility was diagnosed in almost all adults in T1 (98%) and in most leeches of T2 (91%). The number of infants in T1 was significantly (p<0.05) higher than T2. It can be concluded that casein blood substitute feed causes less growth, reproduction and survival rate compared to fresh blood (p<0.05) in H. orientalis. However, due to health and breeding problems, using fresh blood in the reproduction and breeding time intervals of the leeches on the one hand, and the proximity of the results of the two treatments on the other hand, it can be concluded that the blood substitute feed reduces production costs, facilitates feeding of leeches and producing hygienic leeches, hence.

This study was performed to investigate the interaction effects of astaxanthin and beta-carotene pigments in white and red lights on growth performance and coloration of swordtail, Xiphophorus helleri. A total of 180 swordtail with an average weight of 1.4 ± 0.1 g with three diets containing 150 mg/kg astaxanthin, 150 mg/kg beta-carotene and a diet without additive pigment and treatments in contrast to white and red lights with light intensity of 1200 lux was fed in 6 treatments and 3 replications for 8 weeks. Finally, growth indices including body weight gain, specific growth rate, feed conversion ratio and survival rate were determined. In order to determine the number of changes in color intensity and sharpness, Hue and Chroma coefficients were determined after shooting and analyzing the obtained colors using coefficients a and b with Photoshop software in the fourth and eighth weeks. The results revealed that there was no interaction between diets and ambient light, but fish raised in white light were superior in terms of all growth and survival indices (p<0.05). These results also exhibited that the effects of color sharpness (Hue) and red color index (Chroma) were greater in diets containing pigments exposed to white light.

In the present study, the effects of sodium butyrate as a dietary supplement on growth performance, survival rate and carcass composition of beluga, Huso huso were evaluated. After acclimatizing to the rearing conditions feeding with the basal diet for a week, five experimental diets containing 0, 0.1, 0.2, 0.3, 0.4 and 0.5% (T0, T0.1, T0.2, T0.3, T0.4 and T0.5) sodium butyrate were examined on 360 juvenile beluga (average weight 15 ± 0.59 g) for 8 weeks. The studied fish were randomly transferred to 18 experimental 3200-L tanks and a dewatering volume of 1000 L (20 fish per tank). At the end of the trial, growth indices (final weight, weight gain, weight gain percentage, condition factor, specific growth rate, protein efficiency ratio), survival rate (%) and carcass composition were measured. The results showed that sodium butyrate supplementation influenced the growth performance, survival rate and carcass composition of the examined fish. The best growth performance and survival rate were observed in T0.3 (p<0.05). In addition, feed conversion ratio and feed efficiency in T0.3 were significantly better than the control group (p<0.05). Carcass protein of fish in T0.3 was significantly higher, while carcass fat was significantly lower than the control group (p<0.05). Overall, this study showed that 0.3% sodium butyrate supplement in the diet can enhance the growth performance, survival rate and carcass composition in juvenile beluga.

Information on the aquaculture of rainbow trout Oncorhynchus mykiss in brackish water, especially in the Caspian Sea, is very limited. In this study, the growth performance and feeding efficiency of rainbow trout in an enclosed environment (5 floating cages) in an offshore farm (5 km distance from the beach) in the southern Caspian Sea region were investigated. This study was performed in Mehrangostar Caspian Sea farm in the Tuskatok area of Nowshahr City, Mazandaran Province, Iran. The fish were introduced to the cages with a density of 21 fish/m3 and also biomass of 3.33 kg/m3 and weight of 110 to 180 g. The duration of the rearing period and the average survival rate of fish were 123-158 days and 95.8 ± 0.5%, respectively.  In addition, the feed conversion ratio and protein efficiency ratio were 0.94 ± 0.01 and 2.66 ± 0.01, respectively. In this brackish farm, the fish average daily growth rate and the average specific growth rate were 3.3 ± 0.9 g/day and 1.07 ± 0.01%/day. Moreover, the average weight of fish yield was 16 kg/m3. The results showed that the growth trend of rainbow trout in the brackish water of the Caspian Sea in floating cages was suitable. Therefore, the introduction of rainbow trout to floating cages in the southern Caspian Sea by different weights, density of 3.33 kg/m3 and also by managing the harvest of 15 kg/m3 in different times or in a whole single catch is quite possible.

The effects of dietary nucleotide supplementation on growth performance, some serum biochemical parameters, and muscle proximate composition of 240 stellate sturgeons with an average weight of 206.03 g were evaluated during 52 days. Four levels of nucleotide (0, 1, 2, and 3 g/kg diet; T0-T3) were used in three replications. Body weight and length were measured on days 0, 26, and 52 of the experiment in order to evaluate growth performance. Some serum biochemical parameters and muscle proximate composition were also measured at the end of the experiment. The results showed that nucleotide supplementation influenced the growth performance and enhanced some serum biochemical compounds in stellate sturgeon. Body weight, weight gain, and specific growth rate in 26th day were significantly higher in T2 than in T0. At the end of the experiment, these parameters were also higher in all treatments than in control group (p<0.05). However, there was no significant difference between the T1, T2, and T3 groups (p>0.05). The total serum protein and glucose levels were not significantly different (p>0.05) in T1-T3 than in T0 at the end of the experiment. Serum triglyceride and cholesterol levels were higher in the T2 and T3 than in T0 (p<0.05). The results of comparing the mean percentage of protein, fat, moisture, and ash in muscle tissue showed no significant difference at the end of the experiment (p>0.05). Based on the results, using 2 g dietary nucleotide supplement per kg is recommended in the stellate sturgeon farming conditions.