Nutrition Of Freshwater Prawns Grown In Ponds
Natural food items:
Zooplankton and oligochaete worms play a very important role in the nutrition of freshwater prawns grown in ponds. Even juveniles larger than 2g can utilize live zooplankton. Earthworm and insect larvae are also natural food items for the prawns. Enhancement of macroinvertebrate production in ponds is extremely important in the production of freshwater prawns as it would improve feed efficiency considerably. The use of good quality feeds, however, is important when biomass in the ponds increase as the animals grow. Moreover, more uniform production of large prawns is achieved when feeds are used.
Prawn head meal, chicken offal, clam meat, silk worm pupae, meat and bone meal, fish meal, crustacean meal, squid meal and mussel meat meal are some of the excellent ingredients used in prawn feed trials. Various cereal grains, oil seed cakes (ground nut oil cake, soybean cake, sunflower oil cake), rice bran and several other animal husbandry and agro by-products available have also been used as ingredients in test diets. Many of the ingredients are also used in the on-farm and
commercial feeds made in India.
Better growth, molting frequency and survival occurs by feeding animal proteins sources such as mussel meat meal, squid meal, shrimp meal, fishmeal and earthworm meal than plant protein sources such as various oil seed cakes. Best growth performance with least feed conversion ratio (FCR) and highest protein efficiency ratio can be achieved by feeding prawn meal as source of protein than either mussel meat meal or combination of prawn meal and mussel meat meal in a 1:1 ratio.
Meat and bone meal and squilla meal can be used as a replacement of fishmeal for the preparation of efficient practical diets of prawn. Distillers Dried Grains and Solubles (DDGS), an inexpensive ingredient, relatively high in protein (29%), is suitable for use in practical diets at up to 40% of the total formula. Fishmeal can be partially or totally replaced with soybean meal and distillers’ by-products in diets. In addition to the more conventional animal feed ingredients, many other materials (moist pressed brewers’ grains, corn silage, beef liver, orange flesh, peeled sweet potatoes, frozen peeled bananas, turnip greens and carrot tops) can suitably be used for inclusion in prawn diet.
A feed formula using locally available ingredients such as groundnut oil cake, fish meal, soybean meal, rice bran, and vitamin and mineral premix has been developed at CIFA, Bhubaneswar for commercial grow-out of freshwater prawns in ponds.
This formula is helpful for small and marginal farmers who do not use commercial feeds and instead prepare a farm made feeds using mixtures of rice bran, oil cakes and fish or crustacean meal. Chitin supplementation in prawn diet is beneficial for the formation of new shells during molting. Dry sugarcane yeast, Saccharum officinarum, a by-product of alcohol production from sugarcane, could be supplemented up to 20% in a 30% protein diet for grow-out stages.
Addition of several chemo attractants such as taurine, betaine, glycine and proline in diets enhances voluntary feed intake and growth of juveniles. Betaine added to the water has been shown to induce a burst of food searching behavior leading to further intake resulting in a 17% increase in prawn growth at juvenile stages.
Cadaverine at 0.2 % inclusion was the best attractant when compared to other biogenic amines such as putrescine, pheromones (crab urine and freshwater prawn green gland extracts) and squid extracts. However pheromones exhibited good results only with males indicating that these may be more suitable in all-male culture of prawns.
Freshwater prawn is omnivorous and coprophagous.
They have been shown to utilize natural food in preference to artificial feeds. Fertilization, therefore, plays an important nutritional role in pond culture of freshwater prawn. Generally no exogenous feed is required until the prawn biomass reach 18 g/m2 in the pond. Beyond this point natural productivity can no longer sustain growth and feed supply becomes mandatory as a direct source of nutrients. For grow-out culture of prawns feed are initially given at 5-8% of the body weight/day.
The feeding rate declines as the animals grow and reach about 1.5-2% bwd when the animals are about 20 g in size. Broodstock are fed with balanced artificial formulated pelleted feed at 3-5% of the body weight twice daily during morning and evening. Farmers generally feed the cultured prawn twice daily with feeds that contain protein levels ranging from 20 to 35%. However, the species grows well even with 15 % protein feeds in ponds with sufficient natural food.
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