Different carbon sources influences the growth and digestive enzyme activity of grey mullet (Mugilcephalus) in biofloc based nursery rearing system.

Abstract

Aim:To assess the impact of different carbon sources on growth performance of grey mullet, Mugil cephalus fry in biofloc based culture system during nursery rearing phase. Methodology:The experimental trial was carried out for 60 days using three carbon sources, cassava, jaggery and barley in triplicate following a Completely Randomized Design. The carbon nitrogen ratio (C:N) in the systems were maintained at 15:1. Grey mullet fry (0.91g) were stocked @ of 1 fry -1 10 l and were fed with pelleted feed (35% crude protein) @ 4% of fish body weight thrice daily. Results:Significantly higher (P<0.05) growth performance, in terms -1 of Specfic Growth Rate (3.78 % day ) with lower Feed Conversion Ratio (1.35) were found in barley based biofloc group. Similarly, enhanced digestive enzyme activity in terms of amylase (8.78 Unit -1 -1 -1 -1 mg protein min ), lipase (2.77 Unit mg protein min ) and protease -1 -1 (4.22 Unit mg protein min ) were found in barley based biofloc group. Non- specific immune parameters such as lysozyme, respiratory burst activity and myeloperoxidase activity were significantly higher in barley based treatment group followed by jaggery and cassava based treatment groups. Likewise, stress indicators in serum and antioxidant status in liver were found to be lower in barley based treatment compared to cassava and jaggery based treatment groups. Interpretation: Rearing of Mugil cephalus in biofloc culture system is practicable; however, the carbon source required for biofloc production could be barley, compared to cassava and jaggery, in order to achieve maximum growth and to reduce the stress