Influence of fishmeal-replaced diet on nutrient digestibility, digestive enzyme activity, and whole-body fatty acid profile of Indian major carp, Cirrhinus mrigala

Abstract

Background The aquaculture sector is the biggest consumer of fishmeal and the demand of this ingredient is higher than the production. The replacement of fishmeal from aquafeed is a current research thrust. The replacement of fishmeal has been possible with plant ingredients in many fish species, however, possesses some limitations in terms of low digestibility and inadequate nutrient profile. Results Complete replacement of fishmeal in the diets of Cirrihinus mrigala was studied using specially designed nutrient digestibility system. Two feeds were prepared, one with fishmeal as one of the ingredients (control feed) and another with complete plant ingredients (test feed). Initially, forty C. mrigala fingerlings with average weight of 10.88 ± 0.17 g were stocked in six tanks. Fish were fed up to satiation twice daily (10:00 and 16:30 h) for a period of 45 days. After 1 week of acclimatization, fecal samples were collected for 45 days. At the end of the experiment, no significant differences (P > 0.05) were observed for somatic and serum parameters in two treatments. The digestibility coefficient of dry matter, protein, lipid and energy, and three digestive enzymes; amylase, proteases, and lipase did not differ significantly (P > 0.05) between the treatments. The whole body proximate compositions were similar between the treatments. The test diet (containing linseed oil) fed group exhibited higher proportions of whole body linolenic acid (ALA, 18:3n-3). However, eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) did not vary in both studied treatments. Conclusion The information obtained from this study revealed that fishmeal can be completely replaced from the diet of C. mrigala without affecting their growth and nutrient digestibility and fatty acid composition.