Training of Trainers - Library - Network of Aquaculture Centres in ...

content as compared to animal protein sources (60-80%). Further, plant proteins are known to contain imbalancedamino acid composition and contain several anti nutritional factors. Adoption of some of the treatment procedures likedrying, soaking and cooking is suggested in different cases based on the nature and intensity of the anti-nutritionalfactors present in the feed. These research efforts have contributed to improve the various plants and animal basedingredients. Interestingly recent research results now indicate that Pacific white shrimp can be grown almost entirelyon poultry byproduct meal or other plant sources by replacing completely fish meal. In the case of tiger shrimp too, itis shown that with just 10% marine protein source, it is possible to grow to the same productivity level by using otherplant and animal sources of protein. Tilapia and other herbivore fishes can be now be grown largely by using theplant protein sources.(B) Mixed feeding schedules:The concept of mixed feeding schedules was developed by Sena S. De Silva (1985), based on the observed dailyvariation in the digestibility of dry matter and protein in tilapia. Based on the observation, he postulated that fish donot require same level of protein everyday in the diet and feeding feeding alternately with optimal protein diet,followed by sub-optimal protein diet could help in reducing the protein input by several folds. Initial trials conductedwith tilapia demonstrated the benefit of feeding low and high protein at different intervals of time, instead of feedingonly high or optimal level of protein on a continuous basis. Experimental results indicate that it is possible to save 15-20 % protein input and much higher saving in terms of feed cost because of using proteins at two different levels.Most importantly, it also helps in the reduction of nitogen excretion (De Silva and Anderson, 1995). It should bementioned here that nitrogen is not only a costly in put, but also contributes considerably for the eutrophicationprocess with phosphorous. Alternate feeding theory has been now tested and confirmed its suitability not only inrespect of protein, but also fat and phosphorous. This theory is yet to be applied in shrimp and it appears that therewould be large savings in cost by applying this technique.(C) Periphyton based system:Farmers in Asia and Africa have been using different substrates to promote the growth of periphyton in rivers andlakes and thereby attract the fishes to these substrate enriched areas and harvest them by sudden encircling suchplaces with nets.The value of periphyton is increasingly recognized in fishes, which have the grazing habit. Likerohu, which appear to have the fringed lips most appropriate for grazing, is reported to grow rapidly in the periphytonrich water. Addition of substrates is reported to enhance the periphyton abundance. Tree branches, which could serveas shelter to shrimps and fishes and prevent thieves, would also promote good growth of fishes. Bamboo poles, jutesticks, bamboo mats, bamboo scrapings could be other alternatives to explore as substrates. These substratesprovide opportunity for the periphytic organisms to grow – fish like tilapia are known to grow rapidly by feeding onthese substrates. Biodegradable substrates like water hyacinth, sugarcane bagasse, rice straw could also be used.Addition of carbon by these substrates and proper enrichment with nitrogen would contribute for the growth ofheterotrophic organisms in the water column.(D) Fermentation of feed ingredients:Fermented products are known to be easily digestable and also enhance the quality of feed in terms of certainattributes. The technology has also been used to improve the quality of certain ingredients, which are not useful asquality feed ingredients, can be improved through fermentation process. Fermentation process would increase thepalatability as well as the nutrient availability to both fish and prawns. Experimental results conducted with fermentedsoybean flour in shrimp diet have been known to improve the growth as compared to non-fermented product. Forexample rice bran is the most widely used feed ingredient and it is rich in fibre and contains complex carbohydratesin various forms. Efforts are now made to improve the growth through fermentation process.(E) Biofloc technology:103