Quantity evaluation and identification of pathogenic bacteria in water pond and cultivated Cyprinid fish enrichment by natural (cow dong) and chemical fertilizer

The aim of this study was comparison the effect of cow dung as organic fertilizer and chemical fertilizer on microbial flora, fish and human pathogenic bacteria and physico-chemical parameters of cyprinus fish pond water. The water samples were collected from two ponds, pond 1 was fertilized by cow dung and pond 2 was fertilized by chemical fertilizer, respectively from May to October 2011. . The aerobic and anaerobic bacteria were enumerated in TSA by serial dilution of the sample, followed by conventional pure plate method. Coliforms bacteria were similarly isolated on Chrom agarTM ECC. Moreover, the water samples were used to analysis of BOD, dissolved oxygen, conductivity, transparency, total alkalinity, total dissolved solid, total hardness, total nitrogen and total phosphorous. Temperature and pH were measured by thermometer and portable pH meter in place of ponds. For isolating of fish and human pathogenic bacteria, thirty six fish were collected from pond 1 from July to October and then sampled from their liver and kidney and inoculated in blood agar. The mean of total count of bacteria and total coliform count in cow dung sample were 4 × 104 ± 1200 and 4700 ± 300 CFUmL^-1 respectively. The mean of water total count bacteria of pond 1 were significantly higher than the water of pond 2. The water total count bacteria of pond 1 were significantly increased in August, but water total count of pond 2 was not shown significant variation from May to October. The results showed that Pseudomonas, Klebsiella, Enterobacter, Yersinia and E.coli were isolated from water of pond 1 but just Pseudomonas and E.coli were isolated from water of pond 2. Moreover, the human pathogenic bacteria shuc as Shigella and Salmonella were not isolated from of water and fish samples from pond 1. In this study, the bacteria growths were negative in all of the inoculated plate from fish liver and kidney. The total hardness, total phosphorus, total dissolved solid and conductivity of the pond 1 water were significantly higher than the pond 2 water. But the BOD, dissolved oxygen and transparency of the pond 2 were significantly higher than the pond 1 water. There were no significant differences in the total nitrogen, total alkalinity and pH between water of pond 1 and 2. In recent years, the chemical fertilizer has been used in cyprinus fish pond but many studies have showed that they were high risked as environmental pollution. Thus, the use of livestock manure especially cow dung could be a suitable alternative. The results showed the use of cow dung increased the bacterial population and diversity. Increasing of bacteria population caused increased total phosphorus that plays an important role in bloom of plankton because we found decreasing transparency and planktons are an important food for cyprinus fish. In despite of isolation of fish and human pathogenic bacteria from water, the bacteria growths were negative in all of the inoculated plate from fish liver and kidney. In summary, it seems the cow dung is a suitable alternative for fertilizing of cyprinus fish pond water if a microbial and physico-chemical monitoring of fish and pond water were continuously arranged.