Growth and survival of post-larvae of giant freshwater prawn (Macrobrachiumrosenbergii) reared using feeds formulated with different sources of protein.

Abstract

Semi-intensive aquaculture of giant freshwater prawn, Macrobrachium rosenbergii (de Man) in Sri Lanka is limited mainly due to unavailabilty of suitable commercial feeds. At present, the widely used commecial feed is poultry feed starter-I, which is of low nutritive value. Present study was therefore carried out to develop a suitable feed using currently unutilized material as the protein source namely, cattle intestines disacrded from slaughter houses, mussel meat discarded after removing shells for lime and poultry industries, and trash fish discarded at landing sites. Post-larvae of M. rosenbergii having an initial weight of 44-78 mg were stocked in glass tanks measuring 60 cm x 30 cm x 30 cm at a stocking density of 50 individuals per tank and fed with formulated experimental feeds and the poultry feed starter-I as the control diet. Feeding experiments were carried out in triplicate in two culture cycles of 90 days each. Specific growth rates of post-larvae when fed with experimental feeds formulated with mussel, trash fish and cattle intestines as the protein source were 2.08, 2.07 and 2.03 in the first culture cycle and 2.25, 2.27 and 2.33 in the second culture cycle respectively. These were significantly higher than those observed when fed with the control diet which were 1.36 and 1.39 in the first and second culture cycles respectively (p < 0.05). Higher specific growth rates resulted in significantly higher weight gains in post-larvae fed with experimental feeds (458-898 mg) than in those fed with the control diet (217-318 mg) (p<0.05). Survival rates of post-larvae fed with experimental feeds (42-52%) were significantly higher than those of the post-larvae fed with the control diet (16-24%) whereas food conversion ratios of the former (2.47-3.22) were significantly lower than those of the latter (4.90-5.02) (p < 0.05). Present study indicates that lower amounts of feeds formulated using mussel meat, trash fish or cattle intestines as the protein source yield better growth and survival rates of M. rosenbergii post-larvae than the currently used poultry feed starter-I. Since discarded material are used as the protein source, the cost of feed will also be low resulting in high profits.