Research Article
El Araby DA and El-Arabey AA
Abstract
The aim of the present study to assess the use of ethanol extracts of Origanium vulgare as a growth and immunity promoter for Nile tilapia (Oreochromis niloticus L) fingerlings. Fish (Average 12.27 g) were randomly distributed into four treatments; three replicates each at a rate of 20 fish per 100– L aquarium. Fish were fed one of the tested diets containing similar crude protein (30%) and gross energy (4.40 kcal/g). In addition, 0.0, 0.5%, 1.0%, or 1.5% Origanium vulgare extract. Diets were given twice daily at a rate of 3% of live body weight, for six days a week during 10 weeks. After the feeding trial, fish of each treatment were challenged by pathogenic Pseudomonas aeruginosa and Pseudomonas flourscence, which was given by intraperitoneal (I/P) injection and they were kept under observation for 10 days to follow up any abnormal clinical signs and the daily mortality rate. The growth promoting influence of Origanium vulgare extract was observed on fish. The maximum growth was observed at 0.5 % Origanium vulgare extract as compared to the control. No significant differences in fish survival were reported among the experimental treatments, falling within the range of 93.3-100%. The control fish consumed less diet and gave a higher Feed conversion ratio (FCR), while fish fed diet supplemented with 0.5% Origanium vulgare extract demonstrated the highest protein efficiency ratio (PER), apparent protein utilization (APU), and energy utilization (EU). The supplementation of Origanium vulgare extract had no significant effect on the fish body composition (dry matter, crude protein, fat, and ash), mean which total protein, albumin, and globulin increased significantly to the highest values at 0.5% Origanium vulgare extract, as compared to the control. However, supplementation of Origanium vulgare extract did not significantly affect the albumin /globulin ratio (A/G). In conclusion, 0.5% Origanium vulgare extract in Nile tilapia diets increased the fish resistance to Pseudomonas aeruginosa and Pseudomonas flourscence, indicating the effective role of Origanium vulgare extract in disease prevention in tilapia culture. Moreover, the reduction in feed cost compared with the control diet showed 12.52% to produce one kg fish gain of treatment containing 0.5% extracted Origanum vulgare levels.