Histopathologic lesions of juvenile tilapia (Oreochromis niloticus) seen in the addition of effective microorganisms (EM) to swine effluent with varying levels of biological oxygen demand (BOD)

A ten-day experiment was conducted to determine the grass and histopathologic changes in the gills, liver and spleen of juvenile tilapia (Oreochromis niloticus) subjected to swine effluents of varying degrees of biological oxygen demand (BOD) with and without effective microorganisms (EM). All effluent samples showed zero dissolved oxygen levels. Mean BOD and TKN among and between the control and the treated groups showed no significant variations. The temperature and pH measurements fall within the normal range and showed no significant differences. Longer mean survival time was noted in the treated groups. Mean lesion scores for gill congestion was significantly higher in the control groups. Correlation analysis showed very strong associations with both TKN and BOD. Gross lesions noted in the liver include congestion, fatty degeneration and liquefactive necrosis all of which had significantly higher mean lesion scores in the control groups. Inverse associations were noted between both BOD and TKN and the occurrences of such lesions. Meanwhile, the spleen in all groups appeared normal. Histologically, lesions noted in the gills include congestion, hemorrhage, and exfoliation of the gill epithelium, presence of inflammatory cells, necrosis, lamellar aneurysms, basal and lamellar hyperplasia and clubbing of the primary lamellae. Comparison between control and treated groups showed occurrence of hemorrhage and congestion to be significantly high in the treated groups. Correlations of these lesions with TKN were mostly strong. For BOD, correlation was more varied which ranges from inversed to strong linear associations. Lesions noted in the liver include fatty degeneration congestion, edema, necrosis, presence of inflammatory infiltrates and biliary stasis. Comparison of mean lesion scores showed that congestion and necrosis in the control groups were significantly higher. Correlation with TKN and these lesions were mostly strong in both the control treated groups. Correlation with BOD was likewise varied. Lesions noted in the spleen include hemosiderosis, presence of inflammatory infiltrates and necrosis. Mean lesion score for the presence of hemosiderosis and necrosis was noted to be significantly high in the control groups. Correlation with TKN and BOD showed inverse associations. The result of the study show the strong influences of high BOD and high TKN in the occurrences of acute mortalities and development of pathologic lesions in juvenile tilapia. BOD and TKN values obtained indicate positive linear relationships with levels of putrescible organic waste and negative linear relationship with dissolved oxygen levels. While the dissolved oxygen levels remained zero in all groups, lowered BOD levels were observed among the treated groups. This suggests the potential of using EM in alleviating pollution and the improvement of waste water quality.