Effects of carbohydrate supplementation on water quality, microbial dynamics and growth performance of giant tiger prawn (Penaeus monodon)

Biofloc technology based 45-day indoor growth trial was conducted to evaluate the effect of carbohydrate (CHO), molasses supplementation on two developmental stages viz, juvenile (J) and sub-adult (SA) of Penaeus monodon in zero-water exchange system. P. monodon juveniles (1.56 +/- A 0.04 g) and sub-adults (14.32 +/- A 0.22 g) were stocked in fibre-reinforced plastic tanks (1,000 L) with soil base. Carbohydrate supplementation significantly reduced (p < 0.05) the total ammonia nitrogen (TAN), nitrite-N (NO2-N) and nitrate-N (NO3-N) over the time periods in sub-adult group. However, no significant difference in TAN and NO2-N was observed in juvenile-based treatments. Supplementation of carbohydrate significantly increased (p < 0.05) the water and soil total heterotrophic bacterial (THB) count in both juvenile and sub-adults. Despite increase in total Vibrio count (TVC), lower TVC/THB % was noticed in the water column of J + CHO (0.82) and SA + CHO (0.73) compared to control groups, J - CHO (1.48) and SA - CHO (1.21). Supplementation of carbohydrate increased the final body weight in J + CHO (6.51 +/- A 0.44 g) and SA + CHO (22.52 +/- A 0.98 g) compared with respective controls, J - CHO (5.05 +/- A 0.45 g) and SA - CHO (20.00 +/- A 0.33 g). Similarly, significantly lower (p < 0.05) feed conversion ratio and better protein efficiency ratio were recorded in carbohydrate-supplemented juvenile and sub-adults treatment groups. The present study demonstrates that supplementation of carbohydrate reduced the nitrogenous metabolites and significantly enhanced the growth performance of juvenile and sub-adult of P. monodon.