Fish Nutrition and Feed Management
Natural and supplementary feed
Natural food (phyto- and zooplankton, benthos) is produced by fertilization; supplementary feed supplies energy and protein when natural food is insufficient. Common ingredients include rice bran, wheat bran, mustard oil cake, groundnut oil cake, soyabean meal, fish meal, and mineral-vitamin mix. Carp feeds are usually 25-30% crude protein; shrimp feeds are higher.
Formulation and feeding
Balance protein, energy, fibre and minerals; use locally available ingredients; avoid stale oil cakes. Feed 3-5% of body weight daily for fingerlings, less for adults, split into two or three feeds. Use check trays to adjust. On-farm preparation requires drying, grinding, mixing and binding; sinking or floating pellets suit different species.
Worked example
Feed used = 600 kg; initial biomass = 50 kg; final biomass = 350 kg. Gain = 300 kg. FCR = 600/300 = 2.0. If feed costs ₹30/kg, feed cost per kg gain = 2.0 x 30 = ₹60. Reasoning: FCR uses live-weight gain, not final biomass, and feed cost per kg gain is FCR times feed price.
Traps
- Dividing feed by final biomass instead of gain.
- Counting natural food as free when calculating economic FCR.
- Overfeeding, which raises ammonia and FCR.
- Using high-protein feed for adults without considering cost.
- Ignoring check-tray residue.