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XIV. Nutrition and artificial feeding

1. Nutritional requirements of cultivated fish and shellfish

Essential nutrients - proteins (essential amino acids), fats, carbohydrates, vitamins and minerals; animal protein versus vegetable protein; importance of dietary calcium level in fish nutrition; differences in nutritional requirements during different life stages and in different systems of culture; maintenance ration and growth ration; feeding experiments to determine optimal levels of nutrient requirements - controlled experiments and pond feeding experiments.

2. Sources of nutrients

Naturally produced food in ponds, extra food produced through fertilization and supplementary feeding; complete artificial feeds.

3. Effects of feeding

Effects of deficiencies in diet on growth, health and survival; effect of diet on the yield of marketable product from the fed animal - dressing percentage and percentage of edible flesh in live animal and dressed carcass; effects of diet on the composition of gain in respect of protein and fat; effect of diet in causing off-flavours.

4. Evaluation of feeds

4.1 Conversion rates and digestibility of feeds

Methods of assessment; factors affecting conversion rate (composition of food, size of fed animal; frequency of feeding; water quality; temperature, etc.); conversion rates of commonly used feeds; gross energy and percentage of available energy in various types of feed materials; relation of available energy to fibre contents of feed; coefficients of digestion; use of indicators in digestibility studies; biological value of proteins.

4.2 Feed analysis

For determining (i) dry matter, ash, protein, lipids and fibre, and (ii) gross energy, minerals (calcium and phosphorus) and vitamins.

4.3 Analysis of faecal matter

4.4 Estimation of total excretion

4.5 Estimation of growth due to natural food and total growth

4.6 Analysis of fish

For determining dressing percentage, composition of gain and presence or absence of off-flavours.

5. Artificial feeds

5.1 Importance of artificial feeding in intensive aquaculture and its advantages; supplemental feeding; complete feeding; effects of environmental factors (temperature, water quality, crowding, etc.) on feeding.

5.2 Criteria for choice of feeds

Acceptability, digestibility, nutritional value, digestion coefficient, conversion rate, availability, cost, etc.

5.3 Different kinds of artificial feeds

(a) Vegetable feeds; agricultural wastes including oil cakes and mill residues, plants, pulses, cereals, tubers, kitchen waste, etc.

(b) Feeds of animal origin: slaughterhouse refuse, fishery byproducts including trash fish and fish meals, etc.

(c) Compounded feeds:

(i) Advantages and need for compounded feeds, including medicated feeds in aquaculture.

(ii) Feed formulation: feed formulation in relation to species to be fed, feeding habits, age and size of animal, system of culture and availability or otherwise of natural food; general composition of compounded feeds (proteins, fats, carbohydrates, cellulose, minerals, vitamins, binders and water); ingredients commonly used; survey of locally available ingredients and their nutritional value; protein sources - animal proteins versus plant proteins or other cheap sources of protein; factors determining feed and ingredient characteristics (protein, fat, fibre, texture, density, colour and carbohydrate); addition of medicaments for combating diseases.

(iii) Feed manufacture - feed mills and their design; component parts of a feed mill bin, pellet mill, cooler, crumble rolls, sifter and elevator. Production flow: importance of steam conditioning in pellet mill operation; consistency, water stability, texture and particle size; binders used; different forms of compounded feeds (hand pellets, expanded pellets, crumbles, blocks and agglomerates); factors determining pelleting rate and pellet quality (protein, fat, fibre and density); use of pelletability chart; packaging; storage and conservation.

6. Feeding procedure

6.1 Method of feeding

Fresh feed: feeding enclosures for floating feed; feeding baskets/trays for soaked feed; feeding at selected points or broadcasting.

Dry feeds: mechanical dispensers - automatic feeders (fixed or mobile) and demand feeders.

6.2 Feeding schedule

Daily ration in relation to water temperature, size of fish and type of feed; adjustments in feeding schedules to suit temperature and feeding conditions.

7. Economic aspects of different types of artificial feeds and feeding


Formulation and preparation of feeds for selected fish based on locally available ingredients; observation of animal feed manufacture in a feed mill; feeding experiments to study digestibility and conversion rate of selected feeds.

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