The finite supply of fish meal and increasing prices spurred the aqua nutritionists to experiment with several nutritional alternatives to be able to lower fishmeal inclusion levels. However, replacement of fish meal resulted in imbalances in nutrient profile, palatability issues and also reduced immune competency. Therefore, the search for new alternatives having functional nutrients in the health of shrimp has acquired significant importance. Krill meal has quality protein containing balanced amino acid profile, higher phospholipids, EPA and DHA, cholesterol and carotenoids, which are considered as functional nutrients in the diets of shrimp. The present study aimed to assess the potential of krill meal as a functional ingredient in feeds of the shrimp, P.vannamei under two different levels of fish meal inclusion.
An eight-week feeding experiment was conducted to investigate the functional effect of dietary krill meal in diets with moderate (12%) and low (6%) fishmeal concentrations for Penaeus vannamei. Eight iso_nitrogenous and isolipidic diets were formulated to contain 36% crude protein and 5.5% crude lipid. Krill meal was included at 0, 2, 4 and 6%, in both levels of fishmeal included diets. Shrimp with a starting body weight of 0.55 ± 0.02 g were stocked at 22 animals per tank of 350 l capacity and fed three times daily. The influence of krill meal inclusion on various growth performance were assessed ices and the functional effects were studied through biochemical analysis of shrimp, quantification of immune gene expression, hepatopancreas histopathology and hematological indices.
Results revealed that dietary krill meal and fish meal inclusion levels significantly increased growth performance (P < 0.05). Shrimp fed 6% krill meal diet had the highest final body weight of 11.61 g, weight gain of 11.05 g, weight gain % of 1969.38%, specific growth rate of 5.41%/d and yield of 229.42 g/tank. Dietary change did not affect feed conversion ratio, protein efficiency ratio and apparent protein utilization (P > 0.05). Survival was significantly increased in the groups containing 6 and 4% krill meal diets compared to 0% krill meal diet (P < 0.05). Inclusion levels of krill meal showed non-significant differences in post-fed body composition except for crude lipid and crude fibre content. krill meal inclusion levels showed significant variation in the all n-3 fatty acids only. Immune-related gene expression was significantly (P < 0.05) upregulated in the shrimp fed high fishmeal diets (12%) for all the analyzed genes ProPO, PPAE, SP,BGBP,SOD, and HC. The dietary change led to a significant difference in both histology and hematology parameters (P < 0.05). The results inferred that krill meal could be used as a potential functional ingredient in Penaeus vannamei.