Fish Nutrition, Feed Formulation and Feeding Practices
Nutrients and requirements
Carp diets need 30-35% crude protein, catfish and shrimp 40% or more, plus 5-8% lipid, vitamins and minerals. Lysine and methionine are usually the limiting essential amino acids. Feed ingredient reference values you should carry into the exam: rice bran 8-12% protein, maize about 9%, mustard oil cake 30-35%, groundnut oil cake 40-45%, soybean meal 40-45%, fish meal 55-65%. Binders such as tapioca or guar gum hold pellets together in water.
Formulating a simple mash
The Pearson square blends two ingredients to a target protein. Anti-nutritional factors matter: trypsin inhibitor in raw soybean, glucosinolates in mustard cake, gossypol in cottonseed cake, and aflatoxin in badly stored groundnut cake. Feed must be stored dry and used within weeks.
Feeding practice
Feed 3-5% of body weight daily for fingerlings, falling to 2-3% for growers, split into two feeds at a fixed time and place so the fish learn to gather. Use a check tray to see whether feed is being cleared, and adjust the ration when mortality reduces the standing biomass. Grass carp are fed chopped aquatic weeds, often from a bamboo pole feeding frame.
Worked example
Make 30% protein feed from rice bran at 10% and fish meal at 60%. Pearson square: parts of fish meal = 30 - 10 = 20; parts of rice bran = 60 - 30 = 30. Total 50 parts, so fish meal = 20/50 = 40% and rice bran = 30/50 = 60%. Check: 0.4 x 60 + 0.6 x 10 = 24 + 6 = 30% protein. If 480 kg of this feed produces 300 kg of fish, FCR = 480/300 = 1.6, a good result for carp.
Traps that cost marks
- Inverting the Pearson square so the ingredient with the higher protein gets the larger share.
- Calculating FCR as feed divided by weight gain when weight gain is asked, or forgetting to subtract dead fish from biomass.