الفهرس | Only 14 pages are availabe for public view |
Abstract In Egypt, aquaculture is an increasingly important option in animal protein production. Recently, attention has been focused on aquaculture systems, since it has a great potential for achieving other sources of fish production. The Nile tilapia Oreochromis nilolicus, is the most widely cultured tilapia in the world, in particular is accepted to Egyptian consumers. While, the giant freshwater prawn, Macrobrachium rosenbergii, its culture has expanded rapidly not only within Asia but also in regions far remote from the natural distribution of the species. Acidifiers consist of organic acids and salts, they have been used for more than 30 years to reduce bacterial growth and mould in feed stuffs and thus preserve hygienic quality. Nowadays, it is adding to food of human and many animals. This study was undertaken to investigate were carried out to investigate the effect of dietary sodium lactate, calcium lactate and calcium propionate levels as acidifiers on growth, nutrient digestibility, proximate body composition, feed utilization and histological induces of Nile tilapia, Oreochromis niloticus and freshwater prawn, Macrobrachium rosenbergii. In the present study three experiments was conducted: Experiment I, was carried out to investigate the effect of dietary sodium lactate, calcium lactate and calcium propionate at a level of 0, 2, 3 and 4% of O. niloticus fingerlings for 124 days. Experiment II, was carried out to investigate the effect of dietary sodium lactate, calcium lactate and calcium propionate at a levels of 0, 2, 3 and 4% of M. rosenbergii PL for 75 days. Experiment III, was conducted to investigate the effect of dietary sodium lactate at levels of 0, 1, 1.5, 2, 3 and 4% of M. rosenbergii PL for 102 days. Nile tilapia fingerlings with an initial body weight of 10.98±2.63 g were obtained from Saft-Khalid hatchery, El-Behira Governorate, while, freshwater prawn juveniles with an initial body weight 1.54±1.11g and 0.30±0.18g for experiment I and II, respectively from Fish Hatchery, Mariut Company, Alexandria Governorate. Triplicate pens were randomly assigned to each treatment. All pens were supplied with freshwater from the Darawa Irrigation Branch, Kalubiya Governorate twice weekly. After the end of the rearing period the following results were obtained: 1. Experiment I: - The fish fed on diet supplement with 4% sodium lactate improved the growth performance, and the lowest one observed with 2% calcium lactate. - The highest value of the survival rate noticed for Nile tilapia fed on diet supplement with 4% calcium lactate and the lowest one was with 3% sodium lactate. - The best value of FR and FCR were observed with Nile tilapia fed on diet containing 3 and 4% calcium propionate respectively, while PER and EU recorded with 4% calcium lactate. - The highest values of EE and GE observed with fish fed on 3% sodium lactate, while CP recorded with 3% calcium lactate. - The apparent protein digestibility (APD) and lipid digestibility (ALD) improved with fish fed on all organic acid salts comparison with control. Whereas, the best result of APD was observed with diet containing 2% calcium lactate and ALP with 4% sodium lactate. - All treatments showed histological changes of the liver and pancreas of O. niloticus, but the alternation of tissues dilated with increase level gradually. Where, less histopathological changes observed at 2% such as cytoplasmatic vacuolation of hepatocytes, and some congestion of the portal vein in the pancreatic tissue. While, at 4% exhibited high histopathological lesions as pyknosis nuclei and necrosis. - No abnormalities were detected in the ovary tissue of Nile tilapia. But, the histological changes of the testis exhibited with all treatments, but the mild alternations observed for fish fed diet with 2 and 3% calcium lactate and 2% calcium propionate such as slight hemorrhage between seminiferous tubules. But more lesions of testicular tissues noticed with sodium lactate and calcium propionate especially at high level (3 and 4%) such as malformation of seminiferous tubules, degeneration of leydig cells and spermatogonia, increase hemorrhage and necrosis of spermatocytes. 2. Experiment II: - The growth performances improved for freshwater prawn fed on diet containing 2% calcium lactate and 3% calcium propionate. - The survival rate increased for M. rosenbergii fed on diet supplemented with 3% calcium propionate. - The best values of FCR and PER were observed for diet supplemented with 4% calcium lactate. - Dietary 4% sodium lactate decreased all growth performance, Survival rate and feed utilization. - The highest values of CP, EE and GE were observed for prawns fed diet supplemented with 4% calcium propionate. - The histological studies of hepatopancreas showed mild histological effect for prawn at 2 and 3% calcium propionate such as slight increase of R-cell vacuoles, slight decrease of B-cell numbers and mild shrinking of connective tissue. While, more lesion with calcium lactate was exhibited as malformation and swelling of B, R and Fcells. While, No destructions were detected in gonads. 3. Experiment III: - Dietary 1% sodium lactate improved all growth performance and feed utilization of freshwater prawn. - No clear trend was observed as the effects of different dietary Na-lactate levels on proximate body composition of prawn post-larvae, M. rosenbergii except for the higher values recorded for CP and GE at 2% sodium lactate. Also, the survival rate enhanced for prawns fed on 1.5% sodium lactate. - Dietary 4% sodium lactate improved the apparent protein digestibility (APD) and lipid digestibility (ALD). - A mild histopathological change of hepatopancreas for M. rosenbergii at 1% sodium lactate has such as some slough into the lumen, dense materials in vacuoles of Bcells and reduced of lipid vacuoles of R-cells. Whereas, the sections of the gonads exhibited intact at all treatments. The present study recommended that, the best organic acid salts used as acidifiers of O. niloticus is 2% calcium propionate, and of M. rosenbergii is 2 , 3% calcium propionate and 1% sodium lactate for the best biological results associated with the best histological results exhibited with the low levels. |