Nutritive value of copra cake meal fermented with Rhizopus spp. and its use as a protein source in practical diets for rabbitfish (Siganus javus)

ABSTRACT

The aims of this study were to evaluate fermentation of copra cake meal with Rhizopus spp. to enhance its nutritive value and to determine the optimum supplementation levels of the fermented meal on the growth performance and feed utilization of the rabbitfish, Siganus javus. Copra cake meal was fermented with Rhizopus spp. and included in four iso-nitrogenous diets at 0, 150, 300, and 450 g/kg. Rabbitfish (88.3 ± 1.7 g initial body mass) were fed with the test diets at 2.5%–3.0% of biomass/d for 12 weeks. After fermentation, the crude protein content of copra cake increased significantly (P < 0.05) from 218 ± 16 g/kg (mean ± SD) to 293 ± 4 g/kg, while lipid decreased from around 127 ± 4 g/kg to 60 ± 11 g/kg. Total amino acid content of copra cake meal increased after fermentation from 176 ± 12 g/kg to 207 ± 18 g/kg. Based on the third-order (cubic) polynomial regression, inclusion of fermented copra cake meal (FCCM) in test diets had significant (P < 0.05) effects on all parameters observed except for feed intake and survival rate. Fish fed the FCCM0 and FCCM150 diets had a similar protein retention (PR) but significantly differed (P < 0.05) from the diets containing higher FCCM inclusion rates. The breakpoint of two regressions fitted to specific growth rate (SGR) determined that the optimum inclusion rate is 137 g FCCM /kg diet, and at this level, protein from soybean meal can be included at approximately 315 g/kg diet for grow-out of rabbitfish, S. javus, in floating net cages.

KEYWORDS:

• Amino acid
• feed formulation
• floating net cage
• rabbitfish

Acknowledgments

This publication is an output of ACIAR project FIS/2007/124 “Diversification of Small-Holder Coastal Aquaculture in Indonesia.” We also thank Dr. Mike Rimmer (University of Sydney) for editing the manuscript and Dr. Lideman (Brackishwater Aquaculture Development Centre Takalar, Ministry of Marine Affairs and Fisheries, Indonesia) for assisting with the statistical analysis.

Funding

We thank the Australian Centre for International Agricultural Research (ACIAR) for funding this research activity through projects FIS/2007/124 and FIS/2011/038.

Additional information

Funding

We thank the Australian Centre for International Agricultural Research (ACIAR) for funding this research activity through projects FIS/2007/124 and FIS/2011/038.