The present study was designed to investigate the effect of Spirulina platensis (SP) supplemented diets on the growth performance, digestive enzymes, hepatic antioxidants and innate immunity biomarkers in juvenile grass carp (Ctenopharyngodon idella). Two hundred and forty grass carp juveniles (average weight 4.81 ± 0.13 g) were divided into four treatment groups in triplicates (20 fish/replicate) and fed with diets containing 0, 1, 5, and 10% Spirulina for 90 days. A significant increase in growth (p < 0.05) was observed in fish fed with diets having 1 and 5% Spirulina. Intestinal protease and lipase activities increased significantly (p < 0.01) in fish fed with a diet having 5% Spirulina while intestinal amylase activity increased significantly (p < 0.01) in fish fed with diets having 1, 5, and 10% Spirulina. Hepatic lipid peroxidation decreased significantly (p < 0.05) in fish fed with a 1 and 5% Spirulina supplemented diet. The activity of catalase, glutathione-S-transferase, and glutathione levels increased significantly (p < 0.05) in the livers of fish fed with 1% Spirulina supplemented diets while no significant difference (p > 0.05) was observed for hepatic superoxide dismutase levels when compared to the control. Significant increases in the skin mucus protease (p < 0.05), antiprotease (p < 0.01), lysozyme (p < 0.001), and peroxidase (p < 0.05) activities were observed in fish fed with 5% Spirulina-supplemented diets. Gene expression analysis of head kidney showed that fish fed with a 1% Spirulina diet had significantly (p < 0.01) higher expression of tnf-α, il-8, and inf-γ. In conclusion, the present study suggested that the inclusion of 5% Spirulina platensis in the diet of grass carp has positive effects on growth, digestive enzymes, antioxidants, and innate immunity.

The present study aimed to produce a monosex population of all male Nile tilapia (Oreochromis spp.) using 17α-methyl testosterone and common carp testes (as a source of natural androgen). Trial was conducted into two consecutive phases, the first was fry (4-5 days old)administration with negative control (without hormone) and positive control (with hormone) feed viz., MT1:60mg/kg, MT2:70mg/kg (17α-MT), carp testis CT1:70% and CT2:80% for 30 days to reverse the sex of male fish and the second phase was nursing the fingerlings for two months on control diet (32% Crude protein).Results revealed a significant growth rate (P<0.05) in the control group where final weight (4.8±0.34ab) and weight gained was recorded as 0.66±0.03ac. In proximate chemical composition of body meat, CT2 treatment showed maximum retention of crude protein, crude fat, and ash whereas dry matter showed maximum retention in MT2 and CT1 treatments. Morphological and histological examination revealed significant difference (p<0.05) in phenotypic males of Nile tilapia fed with the highest percent in MT-treated diet (MT2) of 95±0.58a while MT1, CT2 and CT1 had males of 85±6.0b, 70±5.0b and 65±6.5b, respectively. It was concluded that synthetic androgen (17αMT) was more effective for masculinization but natural androgen scan be an alternative method to produce male tilapia population in an environment-friendly manner as they are inexpensive, eco-friendly, and radially available. These results suggested that synthetic and natural androgen supplementation in the diet plays a significant role in improving growth performance and body composition.