FORMULATED FEEDS FOR ASIATIC CARPS

D.N. Swamy

1. INTRODUCTION

Feed is one of the major inputs in aquaculture and the success of fish farming depends to a very large extent on the provision of adequate quantities of nutritionally balanced feeds in a form in which fish can utilize. Even when the natural feed forms the main source of nutrition, supplemental feeding with artificial feed is necessary to obtain increased production in ponds as has been shown by Sinha (1979). Fish feeds have been developed in some countries, notably USA, Japan and Sweden for salmonid fishes, cat fishes, eels, carps and shrimps. In most cases, the formulations are propietary secrets and too expensive for use in developing countries. The high cost of some feed ingredients like fish meal has been a problem even in industrially advanced countries and so considerable research is now underway to find suitable substitutes in order to formulate cheaper feeds.

India produces enormous quantities of feed materials derived from crops. These include a wide variety of oil cakes, pulses, mill byproducts of seeds and grains. Also available are smaller quantities of byproducts from the meat, fish and dairy processing industries. Indian fish feed stuffs suitable for fish feed formulation are pods/seeds, leaves/fruits of certain plants, grains, oilcakes, cashew, coconut, gingelli, groundnut, guja, kapu, linseed, safflower, sunflower, soybean, toria, roots and tubers of sweet potato, cassava, cereals and cereal byproducts, broken rice, rice polish, sorghum, wheat bran, maize, etc. Feeds of animal origin are fish meal, prawn meal, meat meal, blood meal, bone meal, hydrodysed poultry feather meal, trash fish, silkworm pupae, aquatic weeds, along with miscellaneous feed stuffs viz., cane molasses, brewer's yeast. Almost all the feed stuffs consumed within the country are by the livestock and poultry industries, and these are also suitable for feeding the fish.

2 CONVENTIONAL ARTIFICIAL FEED FOR CARP

The artificial feed presently used in composite fish culture of carps comprises rice bran and groundnut oilcake in equal proportions by weight. These can be used only as supplementary feeds and the availability of natural protein in the form of plankton is essential. The shortcoming of those feeds in terms of quality becomes obvious when the plankton availability in the pond is poor. Studies conducted at this Centre were aimed at formulating fish feeds using cheaply available ingredients and for upgrading the quality of conventional feed used by pisciculturists.

3 PREPARATION OF BALANCED ARTIFICIAL FEED

3.1 Balancing crude protein level

In most animal diets, protein is the most expensive constituent and is usually the first nutrient that is assessed in diet formulation. The energy level of the diet is adjusted to the desired value by addition of high energy supplements. The “square method” is an easy way to determine the proper dietary proportions of high and low protein feed stuffs. For example, rice bran and groundnut oilcake are available as feed stuffs to prepare a diet for carps with 28 per cent crude protein. A square is constructed and the two feed stuffs are put on the two left hand corners along with the protein content of each. The desired protein level of the feed is placed in the middle of the square. Next the protein level of the feed is subtracted from that of the feed stuffs, placing the answer in the opposite corner from the feed stuffs ignoring positive or negative signs as shown below:

To make 28% curde protein feed, we must mix

If more than two feed stuffs are used in a feed, they may be grouped into basal feeds (CP 20%) and protein supplements (CP 20%) averaged within each group, and plugged into the square method (Crude protein level of fish meal 50%, rice bran 10% and groundnut oilcake 40%).

To make 30% protein diet, we must mix

Fish meal and groundnut oilcake will, however, be required to be mixed in equal proportions.

3.2 Carbohydrates

Carbohydrates are the cheapest and most abundant source of energy for animals. Plants are the major source of carbohydrates in fish feeds. Carbohydrates occur in three basic forms: sugar, starches and fibre. Sugars are highly soluble mono-and disaccharides such as glucose and sucrose. They are usually found in low levels in feed stuffs. The range of carbohydrate found in prepared fish feed for warm water fishes is 15 to 45%. Carbohydrates at levels up to about 25 per cent of the diet are effectively utilized by common carp (Garling and Wilson, 1977). The average crude fibre of the energy feed is about 6 per cent but individual feeds vary considerably in their crude fibre content. Fibre content of upto about 18 per cent in the feed has been shown as not to effect adversely growth in channel catfish (Lovel, 1971).

3.3 Fats

Fats and oils are sources of high energy in the prepared fish feeds, 85 to 90 per cent of which are digestible. About 5% soyabean oil meets the fat requirements of common carp. While fats are good energy sources, they should not be present at excessive levels in the diet because this can lead to high levels of fat deposition in the visceral cavity and in the flosh.

3.4 Vitamins

Vitamins are organic compounds required in trace amounts in the function of most forms of life. In extensive culture and low density intensive culture, natural foods are often abundant enough to provide essential vitamins. In intensive, high density culture such as in heavily stocked ponds or in cages, natural food availability is limited. So, vitamins must be supplied in the supplementary diet as premix to achieve normal fish growth. Generally in fish feed preparation, 0.1 per cent vitamin premix has to be added. Both water-soluble and fat soluble vitamins are required for healthy growth of mrigal fry and fingerlings (Singh and Sinha, 1981; Swamy, 1981 & 1983).

3.5 Minerals

Carps require large amounts of calcium and phosphorus for growth and development. Most of the fish appear to be able to absorb enough calcium from the water through the gills. In fish feed preparation, calcium and phosphorus are added in the form of dicalcium phosphate (1.5%) sodium chloride (0.3%) and trace elements premix (0.1%).

Japanese workers have indicated a requirement of 0.03% calcium and 0.6 to 0.7% phosphorus in the diet for proper growth in common carp.

4 DEVELOPMENT OF PRACTICAL DIET

The prime consideration in the development of practical diets are the local availability of ingredients and their cost. It is better to improve qualitatively the feed extensively used in aquaculture through fortifications.

4.1 Feed Formulation

The aspects to be considered in feed formulation are: (1) nutritional requirements, (2) processing and milling, (3) inherent qualities of feedstuffs including antinutrient factors, (4) other related factors such as binders, etc. Among the more critical nutritional considerations are those placed on the amino acids. The amino acid requirements are expressed as a percentage of total protein. However, the amino acid restriction should be expressed as a percentage of feed. For example, the minimum Lysine requirement for a 30% protein feed should be 1.53% of the feed as compared to 1.84% Lysine in a 36% protein feed. In a least-cost approach, it is not necessary to restrict the total protein content level if the appropriate minimum level of amino acids are set. Other nutritional limitations involve the energy and phosphorus requirements. Vitamins and trace mineral requirements are not considered as restrictions, since complete vitamin premixes and trace mineral premixes are added in fixed amounts in a formulation.

4.2 Larval Diets

Larval diets should meet the nutritional requirements and at the same time be available in such particles for acceptability by hatchlings. Development of suitable larval diets using local feed materials is an important aspect in aquaculture. Encapsulated diet of the desired particle size can be developed from whole eggs (Chow, 1978). Growth response of the hatchlings to egg yolk alone was less than those that were fed with life natural food. This may be due to the protein energy imbalance as also deficiency in some vitamins and minerals.

A freeze-dried preparation of the micro-encapsulated whole egg diet fortified with minerals and vitamins was done for the first time at Fish Nutrition and Feed Technology Laboratory and tested in relation to traditional cakebran mixture, plankton and plankton + traditional feed for the Asiatic carps. To the contents of the poultry eggs are added vitamins and trace elements. These are mixed thoroughly in a mixer. Sodium benzoate is added as a preservative. This is subject to heat treatment in a steam bath. The resultant jelly is freeze-dried and powdered. Each particle has the same composition as the whole egg with 46.8% protein.

4.3 Formulation of Experimental Diets for Fry and Fingerlings

Supplementary feed provided to carps in polyculture at present is a mixture of groundnut oilcake and rice bran in equal proportions by weight. An initial effort in diet development at the FARTC, therefore, was to seek an improvement in the feed value without radically changing the nature and cost of diet mixture now popular among farmers. To determine if such an improvement could be obtained by supplementing the mixture with minerals and vitamins, three diets were formulated, based on groundnut oilcake and rice bran. Two of these diets also contained vitamin and mineral supplements (Table I & II).

Other test diets were also formulated to determine if improvement in feed efficiency could be obtained by substituting groundnut oilcake with seasame oilcake (Table II), the latter being richer in methonine, the essential amino acid generally lacking in vegetable proteins but present at high level in fish meal. The possibility of substituting rice bran with salseed cake was also studied (Table-I).

Furthermore, the possibilities of incorporating aquatic weeds like Salvinia and Hydrilla along with GCC + RB + Bone meal are being examined for grass carp (Table IV).

These formulated feeds were tested for their efficacies in terms of digestibility and growth on fry and fingerlings of rohu, mrigal and common carp.

It was the practice to combine the ingredients and provide a mixture which resulted in disproportionate availability of various components of feed to the cultured fishes. As such, FARTC embarked on pelleting these feed compositions so as to make available all the constituent items to the fishes since pellatization keeps them bound. This also bestowed the advantage of keeping together the vitamins and mineral supplements added for fortification of the feeds which otherwise were apt to be lost in water. Sinking type of pellets were prepared in laboratory model California Pellet Mill.

4.4 Formulated Feed For Brood Stock

Since provision of proper food under artificial conditions is known not only to accelerate growth but also the sexual maturity in common carp, an effort was made to compound a diet for brood stock of Asiatic carps (Table III).

Studies with the feed with 30% protein made of groundnut oilcake and rice bran with fortification and provided at 3% of the body weight of the prospective spawners of Asiatic carps revealed that fishes fed with formulated feed registered better gonadal development compared to the fishes fed with conventional feed. In the case of rohu and silver carp, higher percentage of success in induced breeding was achieved in fishes fed with formulated feed. In catla, grass carp and mrigal also similar results were observed, though tried in limited sets.

4.5 Preparation of Experimental Diets

The experimental diets described above were prepared in the following manner. Rice bran or wheat bran was cooked initially in water added at 120 per cent of the total weight of the diet mixture. The remaining components were first mixed properly and then blended into the hot pasty slurry to form a dough. This was then extruded into pellets by means of a meat mincer fitted with a 3 mm die. The extruded pellets contained about 55 per cent moisture and this can be used as moist type feed. For storage of the prepared feed, the pellets were spread out over a fine screen and dried in the sun. The dried pellets, which contained about 11 per cent moisture, was found to have good water stability (upto 90 minutes) and shelf-life of more than two months when kept in closed containers. Following the installation of the laboratory model pellet mill (USA) during 1982 at the FARTC, the pellets were prepared in the mill using 2 mm die.

5 FEED PROCESSING

5.1 Moist Feed

Moist feeds for aquaculture to start with were from a single ingredient, such as, trash fish for carnivores, crop and vegetable wastes for herbivores. More recent acceptance of the balanced-diet concept gave rise to more complex feeds consisting of two or more main ingredient components together with vitamin and mineral supplements. Though feeds with a high moisture content are generally more rapidly accepted by fish, they have low waterstability. These feeds also lack the commercial attributes of dry diets, such as ease of handling and long shelf-life.

Moist feeds are prepared by adding moisture (approximately 33%) and a hydrocellcidal binding agent carboxymethyl-cellulose, gelatin) or fresh tissue with the dry ingredients and extruding moist pellet-like particles. Advantages of moist feeds are that a pelleting machine is not needed, a food grinder will suffice, many fish species find soft diets more palatable than dry hard diets and that heating and drying which cause nutrient losses, are avoided. Disadvantages are that wet feeds are susceptible to microorganism spoilage unless some preservation measures are followed. The oxygen sensitive nutrients like ascorbic acid are subject to deterioration unless the wet diet is kept frozen (NRC, 1983).

5.2 Pelleted Feed

Pressure applied during pelletization compresses the feed ingredients resulting in the production of dense pellets that would sink rapidly in water. Extrusion, a process through which the feed material is moistured, processed, expanded and dried, produces low density feed particles that float in water. But, cost of production of the latter is higher. Pelleting, on the other hand, is less expensive and the feeds generally cost 10 to 15% less than extruded fish feeds (Feed manufacturing technology, 1976).

Water used, heat provided and pressure applied during pelletization results in formation of homogenous particles of feed. Starch is gelatinized by steam or hot water used and this helps in binding ingredients. Generally, steam increases the moisture content to approximately 16 per cent and temperature to about 85° C.

Floating pellets, on the other hand, require higher levels of moisture, heat and pressure. The mash which contains 25 per cent moisture is compacted and heated to 135°C to 175°C under high pressure before the pressure is suddenly released.

In practical feed formulations, pellet size and acceptability are two important aspects in addition to nutrient level and cost. The considerations are different for each species of fish and will also depend on the type of pellets made. Digestibility of certain feed is enhanced by partial cooking (rice bran) thus raising the metaboliable energy (ME) value (Hardy, 1978). Heat treatment has been found to destroy trypsin inhibitors of soybean meal, thus increasing its nutritional value. Grinding increases the nutritional values of feeds by reducing the particle size and thereby increasing the surface area of ingested feed favouring better enzyme action.

The pelleting and crumbling process helps in compacting the feed ingredients, and increases nutrients density and bulk density. Minerals and trace elements present in the feeds are generally unaffected by processing (Walker, 1978).

Production of dry sinking type pelleted feed appears more practical for feed manufacture with proper selection of ingredients and employing manufacturing procedures designed for high quality pellet production. Thus the products possessing good water stability can be obtained. Use of artificial binders, in most cases, raises the cost of products to prohibitive levels and is avoided whenever possible.

Ingredients should be finely ground so that during the steam conditioning phase, maximum starch gelatinization takes place. This process brings out the adhesiveness of the starch molecule and at the same time increases its digestibility.

Apart from nutritional considerations, dry pelleted feeds have certain advantages like ready availability, long-shelf-life and easy dispensation, while the major disadvantage is of its high cost. Such products are usually made from “conventional” ingredients which have competitive use in the manufacture of feed for livestock. However, good quality compound feeds are usually more efficient and more cost effective than traditional type feed.

5.3 Pellet Binders

Various feed additives increase the durability of pellets, increase water-stability and reduce the amounts of fine particles during manufacture. Although certain feed ingredients and combinations of ingredients will permit the production of good quality pellets, binders are needed to pelletize many fish feeds. Among the most widely used binders are pulverized bentonites, lignosulfonates, hemicellulose, carboxymethylcellulose, and various cellulose derivatives. Wood et al (1954) showed that carboxymethylcellulose at 2 per cent in the diet of trout caused no growth depression.

6 ANTINUTRIENTS

Fish nutritionists and fish food manufacturers must be aware not only of the dietary nutrient requirements of various fish species but also of the antinutrients that might be associated with typical feed stuffs. Antinutritional factors may be natural component of the feedstuff such as gossypol and cyclopropenoic fatty acids in cotton seed meal, phytic acid of many vegetative products, thiaminase present in many raw fish products or the trypsin inhibitor of soybeans. They may also be the result of a natural type of contamination of raw materials such as the aflatoxins produced by the mold Aspergillus flavus which grows on feed stuffs under appropriate conditions of temperature and humidity (Friedman and Shibko, 1972). There are also various man-made contaminants such as the polychlorinated bipheryls pesticides, herbicides and hydrocarbons found in increasing levels in many feedstuffs.

6.1 Moulds and Mycotoxins

Alfatoxins, produced on some feeds by : Aspergillus flavus are not inactivated by normal pelleting procedures. Prevention of mould growth is the best means to avoid contamination. Removal and disposal of mould-damaged material is essential. Certain materials that are sometimes contaminated by aflatoxins such as corn, peanut meal, cotton seed meal, copra, and fish meal should be monitored routinely to check for the presence of aflatoxins.

7 REFERENCES

Chow, K.W. Microencapsulated egg diet for fish larvae. Fish Feed Technology Lecture, 9 Oct-15 Dec., 1978. 355–361 p.

Cowey, C.B. and J.R. Sargent. Fish nutrition. Advanced Mar. Biol. 1972, 10: 383–492.

Dupree and Sueed, 1966. Carbohydrate molecular size in progress in sport fisheries. Fisheries Research 1965. Bureau of Sport Fisheries and Wildlife Res. Pub. 38. pp. 129–130.

Garling and Wilson, 1977. Effects of dietary carbohydrate to lipid rations on growth and body composition of fingerling channel catfish Prog. Fish Cult. 39. 43–47.

Halver, J.E. The nutritional requirements of cultivated warmwater and cold water fish species. Advances in Aquaculture, FAO Tech. Conf. on Aquaculture, Kyoto, Japan, 1976. 574–579 p.

Halver, H.E. Fish Nutrition. New York Academic Press. 1972.

Halver, J.E. Formulating practical diets for fish. J. Fish. Res. Bd., Can. 33: 1032–1039. 1976.

Hardy, R. Fish Food Formulation. Fish Feed Technology Lecture, 9 Oct-15 Dec., 1978. p 233–237.

Hasting, W.H. Nutritional requirements and feed technology. Advances in Aquaculture. Paper presented at the FAO Tech. Conf. on Aquaculture, Kyoto, Japan, 1976 p568–573.

Lovell, R.T. Significant aspects of feed preparation for feeding catfish. In Georgia Nutrition Conference 1971: 101–107.

National Research Council. 1983. Nutritional requirements of warmwater fishes. National Academy Sciences, Washington, D.C.

Swamy, D.N. Feed formulation for carps. Lectures on Composite Fish Culture and its Extension in India for 1983–84 Session of the NACA Training. NACA/TR/83/7. FARTC Sept 1983.7p.

Swamy, D.N. and Hazra, A. 1981. Nutritional requirements for Indian major carps and their feed formulation. Summer Institute on farming system Integrating Agriculture, Livestock and Fish Culture held at CIFRI, Barrackpore, 1981.

Walker, G. Effects of processing on the nutritional value of feeds. Fish Feed Technology Lecture, 9 Oct-15 Dec, 1978. p 321–324.

Wolf, L.E. 1942. Fish Diet Diesease of Trout, a Vitamin Deficiency Produced by Diet Containing Raw Fish. N.Y. State Conserv. Dept. Fish. Res. Bull. 2.2–16.

Friedman, L. and S.I. Shibko. 1972. Non-nutrient Components of the diet pp. 221–226 in Fish Nutrition J.E. Halver, ed. New York: Academic Press. Feed Manufacturing Technology 1976.

Wood, E.M., P.J. Griffin, and S.F. Snieszko. 1954. Synthetic binding of trout diets prog. Fish Cult. 16: 19–24.

Sinha, V.R.P., 1979. On the contribution of Supplementary feeding in increasing fish production through Composite Fish Culture in India. Proc. World Symp. On Fin Fish Nutrition and Fish Feed Technology, Hamburg, West Germany 20–23 June 1978. Vol.II.

Singh, B.N. and V.R.P. Sinha, 1981. Observations on the nutrition of Indian major carp Cirrhinus mrigala (Ham) (Abstr.). All India Seminar on Fish Biology, Bihar University, Muzaffarpur, Nov. 26–28, 1981, p-21.

TABLE I

FORMULATED DIET FOR CARP FRY

Trace mineral mix made from: C₄SO₄.5H₂O, FeSO₄.7H₂O, MnSO₄.H₂O, Znc, Cocl2.6H₂O, KI and CaHPO₄ filler to provide the following (ppm total diet) C₄, 10: Fe 100; Mn 50; Zn 50; Co 0.05 and KI 10.

Vitamin Mixture to provide the following (Per kg total diet) vitamin A 5000IU, Vitamin D, 600 IU, Thiamino, 10 mg, riboflavin 20 mg, Pantothenic acid, 30 mg; niacin 50 mg and ascorbic acid 200 mg.

Table-II

FORMULATED DIET FOR CARP FINGERLINGS

TABLE III

FORMULATED DIET FOR BROOD STOCK

Additional vitamins added were vitamin E one tablet for 1 kg diet Vitamin C 200 mg for 1 kg diet.

TABLE IV

FORMULATED DIET FOR GRASS CARP FRY AND FINGERLINGS