Exploring the potential of Averrhoa carambola extract for enhancing growth and immunity in Labeo rohita in hill aquaculture of North-east India

The growth, immunity and overall condition of fish in hill ecosystems remain suppressed due to prolonged cold climates. To address this issue, we assessed the effect of feeding fish (Labeo rohita; 6.41±0.34 g 6.17±0.34 cm) with a diet containing Averrhoa carambola var. sweet large extract as feed additive. The study was undertaken in 1 m3 cemented cisterns, with 30 fish per tank. They were fed daily with diets containing different concentrations of carambola extract (CE): 0% (control group), 2 and 4%, equivalent to 3% of their biomass. Water quality parameters were assessed fortnightly, while monthly evaluations measured fish growth attributes. Fish were sampled on 15th, 30th and 60th day of the feeding trial for analysis of growth and blood parameters. Results showed a significant increase in specific growth rate (SGR), with a 49.5% boost in the group fed with CE-incorporated feed. Survival rates ranged from 86.7 to 88.4% for fish fed with CE, compared to 78.4% for the control group. Fish fed with 4% CE displayed positive allometric growth. Blood analysis revealed increased RBC and WBC counts, higher haemoglobin and total protein levels, and decreased glucose and cholesterol content. Serum glutamic oxaloacetic transaminase (GOT) and glutamic puruvic transaminase (GPT) activity remained normal. The optimal results were observed with a 4% CE inclusion in the diet. In conclusion, including carambola extract in fish feed effectively improved fish growth, condition and immunity. These findings are valuable for enhancing aquaculture strategies in hill ecosystems Keywords: Blood parameters, Carambola, Condition factor, Fish feed, Growth rate, Hill ecosystems, Indian major carps