فصلنامه تغذیه آبزیان
پیاپی 1 (بهار و تابستان 1394)

To evaluate the effects of thiamine (vitamin B1) on physiological changes and reproductive performance of Sterlet sturgeon (Acipenser ruthenus), 30 females (averaged 698 ± 15 g) were selected in maturity stage IV and were randomly distributed in six fiberglass tanks (1063.3 liters) with two treatments and three replicates. The first treatment was fed with a dry diet containing 10 mg/kg thiamine hydrochloride, while second one was fed with 1 g/kg amprolium hydrochloride as an anti-thiamine compound for five months. After this period, fish were induced for spawning by LHRH-A2. At the end of the experiment, the growth parameters showed no significant differences between treatments (P>0.05). In the first treatment (fed with thiamine), the levels of hematocrit and hemoglobin were significantly increased (P0.05). Germinal vesicle migration was measured in three stages (day 0, 75 and 150) which had a significant decrease in thiamine-fed treatment (P0.05) between the treatments, while a significant increase in testosterone were observed in thiamine-fed treatment (P0.05). According to the results, the presence of thiamine in the diet led to improvement in some physiological and reproductive indices in Sterlet sturgeon and it seems to be an essential vitamin in reproduction season for Sterlet broodstocks.

The development of proteolysis digestive enzymes from the stomach and pancreas were studied in Beluga, Huso huso from hatching up to 50th day post hatching (dph). Larvae were obtained from ShahidMarjaniSturgeonRearingCenter, Gorgan province, Iran. Sampling was carried out immediately after hatching, 7, 14, 19, 24, 29, 35, 42 and 50 dph. The results showed that at the onset of exogenous feeding, gastric glands were already functional, which was indicated by an increase in proteolitic activity of stomach. In contrast, proteolitic activity of pancreas decreased after the onset of exogenous feeding, showing the importance of these types of enzymes in the cleavage of yolk proteins during the endogenous feeding phase. The present study indicated that larvae of Beluga at the onset of exogenous feeding had an advanced digestive system to accept exogenous food and to digest the formulated diets.

To investigate the effect of dietary supplementation of L-carnitine on growth and carcass composition of Sobaity fry, an experiment was carried out on 240 pieces of Sobaity Seabream (Sparidentex hasta) averaged 3.01 ± 0.03 g in initial weight for 10 weeks. Experimental treatments consisted of four levels of 0, 500, 1000 and 1800 (control, L-C500, L-C1000 and L-C1800) mg L-carnitine per kg of diet, each with three replicates in a completely randomized design. During the experimental period, feeding was performed by hand and the fish were fed to satiation three times a day. At the end of the experimental period, bodycomposition including crude protein, crude fat, moisture and ash contents were analyzed. Significant differences in growth parameters such as final weight, FCR, SGR, PER, GR and BWI% was observed among treatments (P

In this study, the effects of probiotics bacilli on the feed efficiency and carcass quality in rainbow trout, Oncorhynchus mykiss, fries were studied using a commercial product Protexin Aquatech. A blend of five strains of probiotic bacilli (Basilus licheniformis, B. subtilis, B. polymyxa, B. laterosporus and B. circulans) was used through the supplementation of diets for 60 days. Fish fry with an average weight of 463 ± 32 mg were used. The experimental diets were supplemented with mixture of the five bacilli at concentrations of 1×106 (D1) 1×107 (D2) and 1×108 (D3), (CFU per 100 g food), and a control (probiotics-free diet). The feeding rate was varied between 5 and 8% of body weight. The results indicated that D2 treatment had significantly better growth and feed conversion ratio than the control group and D1 treatment. Results showed that in the experimental treatments, probiotics had a significant positive effect on protein efficiency ratio, lipid efficiency ratio and protein productive value compared to the control treatment (P

Aquatic animals are important resources for extraction of valuable compounds such as enzymes. In this study, lipase was extracted from the intestine of rainbow trout. Samples were defatted with acetone several times; ammonium sulphate (60%) was used for precipitation followed by ultrafiltration for concentrating the samples. The final purification of the enzyme was performed by passing of the samples through G-75 column chromatography. After extraction, effects of two inhibitors were investigated on the activity of the enzyme. The enzyme activity was assayed by p-nitrophenyl palmitate as a substrate. The results showed that Ethylenediaminetetraacetic acid and Phenylmethylsulfonyl fluoride had significant inhibitory effects on the lipase activity (P

Increasing production and utilization of silver nanoparticles can lead to their release into aquatic ecosystems and tend to toxic effects on aquatics. It is not yet clearly specified whether observed toxic effect following exposure of aquatic organisms to colloidal nano-silver is caused by silver nanoparticles contained in the colloid, by free silver ions, or by a combination of both. In this study, acute toxicity of "nanosilver colloid" (containing free ionic silver and silver nanoparticles) compared to the toxicity of "silver nanoparticles" separated from colloidal nanosilver (without free Ag ions) were investigated in zebra fish, Danio rerio. Acute toxicity tests were planned and performed according to standards of Organization for Economic Cooperation and Development. The results showed that No Observed Effect Concentrations (NOECs), Lowest Observed Effect Concentrations (LOECs), Maximum Acceptable Toxicant Concentrations (MATCs), and Median Lethal Concentrations (LC50s) of "nano-silver colloid" were 250, 240, 248.90, and 300.64 times less than those of "silver nanoparticles", respectively. Therefore, toxicity of colloidal nanosilver is mostly due to the free silver ions (Ag) rather than silver nanoparticles present in it. In general "nano-silver colloid" and "silver nanoparticles" are respectively classified as "highly toxic" and "toxic” chemicals for aquatics and the release of these substances into the environment should be prevented.