|
|
:
|
This study aimed to evaluate the effects of feeding with different types of live feeds (Chironomid larvae and Artemia biomass) on growth performance, survival rate, body composition, fatty and amino acids profile and activity level of digestive enzymes of Beluga sturgeon (Huso huso) larvae during short-time (21 days) and long-time (42 days) weaning to dry feed. Afterward, the fish were fed with frozen Chironomid larvae (CHFD-21), frozen Artemia biomass (ABFD-21), and a combination of them (MFD-21) for 21 and 42 days. The control group (C) received only dry feed throughout the feeding trial as 7 treatments and each in three replicates. At the end of each acclimatization period, growth performance, chemical composition of the whole fish body, fatty acid and amino acid profile of the body and determination of the activity level of digestive enzymes of Beluga larvae were evaluated. The results showed the final weight, weight gain, body weight gain increase and specific growth rate in CHFD-21 were significantly higher than other experimental groups and there was no significant difference between other treatments in terms of growth indices. Survival rate of beluga (Huso huso) in the control treatment (C) decreased significantly compared to other treatments (P < 0.05) and no mortality was observed in the group fed with frozen blood worm larvae (CHFD-21) (P < 0.05). Beluga larvae fed with frozen Chironomid larvae showed the lowest total fat and protein percentage. The amount of ash in the treatment fed with chironomid food was significantly higher than the other groups. According to the results, Beluga larvae fed with frozen Chironomida larvae showed the lowest total body fat and protein percentage. The amount of ash in the treatment fed with Chironomis food was significantly higher than the other groups. The results obtained from the present study showed that the composition of the carcass of Beluga sturgeon larvae in the nutritional treatments during the period of 21 days was less than 42 days. MFD-21 group showed a significant decrease in total PUFA fatty acids compared to CHFD-21 (P < 0.05), but this difference was not observed in the 42-day habituation treatments, and PUFA in larvae fed with concentrate food in each two strategies were more habituation than other treatments. The ratio of EPA/DHA in CHFD-21 group was significantly higher than other treatments and also higher than CHFD-42 and lower than feeding with concentrate food (P < 0.05). The total of essential amino acids and the ratio of essential to non-essential amino acids of the treatments in 21 and 42-day habituation did not have significant differences (P < 0.05) and the total of essential amino acids and the ratio of essential to non-essential amino acids in 21 days of habituation was more than 42 days. The highest and lowest activity of trypsin enzyme was observed at the end of the experiment (day 42), in CHFD on day 10 of the experiment and C on day 21 of the experiment, respectively. The results of lipase enzyme activity in 21 and 42-day habituation treatments at the end of the 21st day showed that lipase activity in CHFD was the highest in 21-day habituation and the lowest in 42-day habituation. Also, on the 21st day, there was no significant difference between feeding on Chironomide and feeding on concentrate food in 21-day habituation. The highest level of alpha-amylase activity was observed in ABFD (Artemia biomass) treatment at 21 days and the lowest level in MFD (mixed diet of Chironomida and Artemia biomass) at 42 days. Alkaline phosphatase activity at the end of the 21st day in the treatment fed with concentrate food was the highest in the 21-day habituation and the lowest in the 42-day habituation. In general, the consumption of Chironomid alone in the habituation of 21 and 42-day-old Beluga larvae to dry food, due to its role on the growth performance, survival and improvement of body composition and fatty acids and essential amino acids, did not show much difference, but due to the high cost of Chironomid and Also, if there is a quality larval concentrate food, it is recommended to use Chironomide's food for a period of 21 days.
|