WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2014 67 medicines as immunostimulants of fishes (Sakai 1999, Shao et al. 2004, Vasudeva et al. 2006). Immunostimulants can be given alone to induce in vitro and in vivo responses (Jian and Wu 2004, Innocent et al. 2012). Plant-derived substances incorporated into standard fish feeds may elicit a specific humoral response and then enhance host defense mechanisms (Campanjen et al. 2006, Innocent et al. 2012). Total and differential leucocyte counts are important indices of non-specific defense activities in fish (Pedro et al. 2005) because leucocytes are centrally involved in phagocytic and immune responses to parasitic, bacterial and viral invasions (Houstan 1990). Thus, significant increase in the TLC, neutrophils and monocytes in striped snakehead fingerlings fed the diet with the herbal supplemented can be attributed to the non-specific immune response and increase in lymphocytes, which may be a specific pathogen-induced immune response. Using herbal additives such as P. niruri in feed may reduce the risk of disease outbreaks in aquaculture (Sakai 1999, Shao et al. 2004, Vasudeva et al. 2006, Haniffa and Kavitha 2012). Acknowledgments Authors acknowledge the financial assistance received from ICAR-NAIP Sub Project entitled, “A Value Chain on Murrel Production in Tamil Nadu and Orissa” (F.No.1(5)/2007-NAIP dt. 22 Aug. 2008). We are grateful to Rev. Dr. A. Joseph S.J., Principal and Consortium Leader, St. Xavier’s College (Autonomous), Palayamkottai, for providing the necessary facilities. We thank B. Kavitha Bharathi and P. Jeya Sheela and Bilal Ahmad Paray for contributions to the study and preparation of the manuscript. TABLE 2. Growth response of striped snakehead fingerlings fed a diet supplemented with P. niruri. Parameter Control diet Experimental diet Initial length (cm) 4.9 ± 0.4 4.9 ± 0.4 Final length (cm) 7.9 ± 0.4 9.3 ± 0.3 Initial weight (g) 1.0 ± 0.2 1.0 ± 0.2 Final weight (g) 3.9 ± 0.7 6.2 ± 0.5 Weight gain (g) 2.9 5.2 SGR 2.6 3.6 Condition factor 0.76 0.78 TABLE 3. Effect of P. niruri administered diet on hematological changes in striped snakehead. Blood parameter Control diet Experimental diet Hemoglobin (g/dl) 11.5 ± 0.2 12.1 ± 0.1 Hematocrit (%) 36.3 ± 3.0 36.4 ± 4.2 MCV (fl) 11.3 8.5 MCH (pg) 3.57 2.81 MCHC (g/dl) 31.6 33.2 RBCS (106/mm3) 2.61 ± 0.34 2.68 ± 0.04 WBCS (103/mm3) 40.0 ± 3.1 45.6 ± 0.8 Lymphocytes (%) 25.2 30.7 Neutrophils (%) 12.0 17.0 Monocytes (%) 10.4 13.9 Eosinophils (%) 6.0 8.3 FIGURE 2. Weight gain of striped snakhead fingerlings fed a diet supplemented with P. niruri. blood was used for the analyses of blood variables except Differential Leucocyte Count. Total Erythrocyte Counts (TEC) and Total Leucocyte Counts (TLC) were estimated using hemocytometer with improved Neubaurer ruling chamber. Hemoglobin content was measured following cyanohemoglobin method using Drabkins fluid. For differential leukocyte count, six blood smears for each fish were prepared from fresh blood, air-dried, stained with LeishmanGiemsa’s stain and fixed in methanol. In each sample, three visual fields at 1000× were identified for the leukocyte count (Harikrishnan et al. 2003) and the proportion of neutrophils (NEU), eosinophils (EOS), lymphocytes (LYM) and monocytes (MON) was determined. The derived blood indices of mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) were calculated using standard formulae suggested by Dacie and Lewis (2001). Administration of P. niruri in the diet resulted in elevated WBCs and hemoglobin compared to blood of fish fed the control diet. The proportion of lymphocytes, neutrophils, monocytes and eosinophils in fish fed the diet supplemented with P. niruri was greater than those of fish fed the control diet (Table 3). Discussion In this study, the growth of striped snakehead fingerlings fed a diet containing P. niruri was greater than that of fish fed the control diet without the herbal additive. Ahilan et al. (2010) reported that the addition of P. niruri enhanced the growth of goldfish Carassius auratus. The herb promotes cellular lipid and fatty acid utilization and protein accumulation, resulting in better growth performance in fishes (Ji et al. 2007, Haniffa and Kavitha 2012). In aquaculture, there are reports on the use of herbal (CONTINUED ON PAGE 68)
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