Fish Nutrition, Feeds and Feeding Practices
What the exam tests
Nutrition and feeding questions cover nutrient requirements, feed ingredients, feed formulation, feeding rate and efficiency. You should be able to calculate FCR and feed cost and to choose supplementary or complete feeds for carps and catfish.
Core rules
- Protein requirements are higher for fry and catfish than for grow-out carps; typical carp grow-out feeds contain about 25 to 30 percent protein.
- Energy, vitamins and minerals must be balanced; excess protein is costly and increases ammonia.
- Common ingredients include rice bran, mustard oil cake, fish meal, soybean meal, maize and mineral mixture.
- Feed conversion ratio (FCR) = feed given divided by fish weight gain. Lower is better.
- Feed 2 to 5 percent of body weight daily, split into smaller meals; adjust for size, temperature and natural food.
- Store feed cool and dry to prevent mould and rancidity.
Worked example
A farmer uses 100 kg feed and harvests 50 kg extra fish. FCR = 100 / 50 = 2.0. If feed costs Rs 30 per kg, feed cost per kg of fish gain = 2.0 x 30 = Rs 60. Reasoning: FCR links feed input to gain; multiplying by feed price gives the feed cost per unit gain.
Traps
Do not treat a high FCR as good. Do not ignore natural food in semi-intensive ponds. Do not feed raw soybean without heat treatment. Do not overfeed; uneaten feed fouls water.
Key facts
SGR measures growth rate. Floating pellets allow observation of feeding. Feed records are essential for economics.