Impact of fishmeal replacement with Arthrospira platensis on growth performance, body composition and digestive enzyme activities of the freshwater prawn, Macrobrachium rosenbergii

• The main aim of the present study is that the fishmeal was replaced in the aquatic animals feed with alternative protein source of Arthrospira platensis.
• The present study related previous researchers reported fishmeal replacement was 5–30% or partial level only. But, the present study report in the range of fishmeal was fully replaced by alternative source (Arthrospira platensis).
• The present study shows the fishmeal was replaced with the Arthrospira platensis up to the range of 50% level.
• The 50% replacement of fishmeal was replaced with Arthrospira platensis which significantly affect the growth and biochemical constituents of the freshwater prawn Macrobrachium rosenbergii postlarvae.
• So, the present study suggesting the fishmeal was replaced in feed formulation for Macrobrachium culture with Arthrospira platensis meal up to the range of 50%.

In this study, we assessed the suitable level of replacement of fishmeal with a blue green microalga, Arthrospira platensis in feed for the post larvae (PL) of the freshwater prawn, Macrobrachium rosenbergii by evaluating the growth performance, prawn proximate composition, feed utilization parameters and the activity of digestive enzymes. The prawns were fed 5 different diets: a control diet and 4 different diets containing A. platensis at various levels such as 25%, 50%, 75%, 100%. These diets were fed to the PL for 90 days in triplicates. The growth performance in terms of weight gain, specific growth rate and feed efficiency ratio were found significantly (P < 0.05) higher in the prawns fed with the 50% of A. platensis feed fed group. At this level of 50% replacement, the prawn proximate composition, such as total protein, amino acids, carbohydrates and lipid contents were significantly (P < 0.05) higher than the control. Similarly, feed utilization parameters, such as feeding rate, absorption rate and conversion rate were significantly (P < 0.05) higher than the control. Added to that, the activity of the digestive enzymes such as protease, amylase and lipase showed the same trend at the level of 50% replacement. The hierarchy of the growth performance in prawns corresponds to 50 > 25 > 75 > 100% replacement of fishmeal with A. platensis. These results concluded that a partial replacement of the fishmeal with A. platensis at the level of 50% is beneficial for the growth of prawn M. rosenbergii.