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Abstract
The study has used probiotics in water environment management of intensive whiteleg shrimp ponds with canvas in coastal water at the high-tech aquatic seed production area of Dac Loc Aqua. Co., Ltd. (hamlet 4, Xuan Hai commune, Song Cau town). Two experiments were conducted with different the used mode of probiotic: ponds using daily use of probiotics, 0.5 -1.0 g / m3 of water (equivalent to 2-4 kg / pond 4,800 m3 of water); ponds using probiotics periodically: The first month of farming, 7 days / times, the dose of 2.0 g / m3 of water; 2nd farming month, 5 days / times, dose 3.0 g / m3 of water; 3rd farming month, 3 days / times, dose 5.0 g / m3 of water. Probiotics have contained the main microoganisms strains: Bacteia Nitrosomonas sp.,
Nitrobacter sp. and the fungi Saccharomyces sp. Analysis of shrimp samples and ponds water showed that, in ponds using probiotics periodically, Vibrio density in shrimp (from 9,0 × 101 to 3,9 × 102CFU/g) and water samples (from 5,0 × 101 to 8,2 × 102CFU/ml) was lower, environmental parameters such as clarity, pH, DO, NH3 and NO2- were stable and is within the permitted level compared to ponds using daily use of probiotics. After 75-80 days, the yield of whiteleg shrimp harvested in ponds using probiotics periodically were 1.3 times higher than in ponds using daily use of probiotics; the feed conversion ratio (FCR) and the havervested whiteleg shrimp size (individual per kilogram) were also respectively lager (FCR=1.29 comparated to FCR=1.41; havervested whiteleg shrimp size = 64.3 inds./kg comparated to 81.5 inds./kg). The number of probiotics used in ponds using probiotics periodically are only 65.6% of the amount of inoculants used in ponds using daily use of probiotics. That has shown that the recurring probiotics use is more effective than daily use.
Key words: White leg shrimp, coastal water, probiotics