Non-specific immune responses in juveniles of Indian major carps

Summary The non‐specific immune parameters are useful to determine the health status of fish and to evaluate the immunomodulatory substances for fish farming as markers of pollution and disease resistance. Some of the important parameters, viz. superoxide production by neutrophils through nitroblue tetrazolium (NBT) assay; haemagglutination (HA), haemolysin (HLY) and bacterial agglutination titres; myeloperoxidase (MPO), and lysozyme activities, and alternative complement levels in serum of the juveniles of three Indian major carp species (Cirrhinus mrigala, Catla catla and Labeo rohita) were measured to establish their physiological normal range. A wide variation among the individuals within a species in the ranges of the most of the immune parameters was recorded. Significantly higher levels in the mean values of HA, HLY, bacterial agglutination titres; superoxide production by neutrophils in nitroblue tetrazolium assay; serum MPO and lysozyme activities, i.e. 371.20, 4.60, 18.80, 0.40, 0.62 and 6.55 μg ml−1, respectively, were obtained in L. rohita except a much lower alternative haemolytic complement activity (29.06 units ml−1) compared with the other two species. In most of the parameters, L. rohita showed the highest value, possibly indicating its more natural resistance compared with the other two species.