Studies on Fish feed Formulation of Indian Major Carps from Aquatic Macrophytes, Lemna minor and Eichhornia crassipes

In the present study, highest SGR (Specific Growth Rate) was obtained in 20% in Lemna minor and 10% in Echhornia crassipes. The leaves of aquatic plants had considerable amount of crude protein and crude lipid, which improves the growth of fingerlings of fish upto a certain levels of inclusions, thereby reducing the feed cost. The slow growth performance might be due to absence of natural feed in the laboratory culture. The leaf meals inclusion has much advantage in growth performance of fish. However these leaf meals need processing to lower their fibre content, which to be used as fish feed.


INTRODUCTION
Artificial feed plays an important role in semi intensive fish culture, where it is required to maintain a high density of fish than the natural fertility of water can support (Jhingran, 1991). Feed is undoubtedly the single largest operating cost in intensive fish culture especially using cat fish, which needs high protein (Otubusin et al. 2007). Proteins are major organic material in fish tissue constituting 65%-75% of dry weight (De Silva, 1989). Lipids constitute 6.28% of fish diet. Lipids for fish are important source of energy and help in transportation of fat soluble vitamins and steroids. Essential fatty acids promote normal larval development, fish growth and reproduction (Mishra and Mukhopadhaya, 1996). Fish feed generally constitute 60%-70% of operational cost in intensive and semi intensive aquaculture systems (Singh et al., 2006). To increase protein retention from the diet, the quality and mixture of different proteins and the inclusion of partly pre-digested proteins have shown good results (Calheires, 2003, FAO, 2004, Lunger et al., 2007.

MATERIALS AND METHODS
Feed Ingredients: Fish meal, ground nut oil cake, rice bran, soybean meal were collected from local market. The two aquatic weeds used in the feed, Lemna minor and Eichhornia crassipes were collected from local water bodies.
Feed Additives: Sunflower oil, Cod liver oil and Vitamin mineral premix. Cod liver oil and vitamin were collected from local medicine store. For vitamin mineral premix Ambiplex, Brihans lab, Pune and Argimin, Glaxo India Ltd., Mumbai was used. Sunflower oil was collected from local grocery store.
Equipments Used: Mixer grinder, Sieve, Balance, Pelletizer Preparation Method: The feed ingredients other than leaf meal were collected from local market and sundried. They were grounded thoroughly and passed through fine meshed sieve to ensure homogeneity. Lemna minor and Eichhornia crassipes plants were collected from local water bodies. Leaves were collected in case of Eichhornia and sundried. Dried leaves were grounded thoroughly and sieved to obtain fine powder. Powdered ingredients were subjected to proximate analysis following procedures of AOAC (2000).

Proximate Analysis
Moisture: Weighed amount of sample (W1) was placed in the oven for 12 hours at 105˚C. The dried sample again kept in oven until constant weight (W2) was obtained. The loss weight was recorded.

RESULTS AND DISCUSSION
Proximate analysis of feed ingredients such as fish meal, soybean meal, GNOC, leaf meals were made (Table-1). Crude protein (% CP) of fishmeal was 63.02, ground nut oil cake was 42.5 and soybean meal was 35.3 and rice bran 12.3. The leaves of two aquatic macrophytes contains 20.3%, crude protein (Lemna minor) and 13.5% (Echheronia crassipes) respectively. Crude lipid (CL %) content of the fishmeal was 11.3%, followed by rice bran and GNOC which were 10% each and soybean contained 20% CL. The two leaves used had CL content of 4.3% and 2.6% in Lemna and Eichhornia respectively. Ash content was highest in fishmeal (22.75%) followed by Eichhornia leafmeal (21.7%) and was lowest in Lemna minor(13.5%). Ricebran had 8.5% ash and soybean had 5% ash.     Most conventional ingredients used in fish feed are fishmeal, soybean meal, groundnut oil cake etc which in developing countries are scarce and costly to farmers (Fasakinet al., 1999) causing hardship of gaining due profit from aquaculture. Fishmeal is often used in aqua feeds as they are essential source of amino acids, vitamins and minerals and they generally enhance palatability (Davies and Arnold, 2000). However, nearly all researchers agree that an alternative ingredient should be used in aqua feed industry in place of fishmeal, whose supplies are limited although demand for it is expected to rise (Yilmaz et al., 2005).
Considerable attention has been devoted to replacement of fishmeal with plant protein sources such as soybean meal (Oliva Teleset al., 1994), groundnut oilcake (Davies and Ezenwa, 2010), muccuna seed meal (Sidduraju and Becker, 2001), winged bean (Fagbenero, 1999) and various legumes (Hossain et al., 2001). Now day's serious efforts are made towards use of non conventional feed sources as ingredients in fishfeed (Ali et al., 2006). Utilization of aquatic macrophytes commonly occurring in freshwater bodies can serve two benefits at a time. 1. These may be used as alternative ingredients for making farm based aquafeeds, and 2. Their use as ingredients in making fishfeed can reduce their wastage and minimise cost of fishfeed production along with supply of sufficient nourishment to fish without affecting the ambient environment (Mandal et al., 2010). With high abundance as well as excessive proliferation, aquatic macrophytes are easily available in fresh water ecosystem (Mandal et al., 2010). However their utilization as fishfeed component is not much remarkable despite their unique nutrient status (Mandal et al., 2010). Lemna minor is found to be the most promising one, 40% of which is blended with commercial feed has exhibited significant performance (Elsafai, 2004) advocated inclusion of 20-40% duckweed in fish diet on dry weight basis as it had better digestibility Coefficient than any other commercial plant material used. Stetlikova and Adamek (2004) opined that Elodea Canadensis as having higher concentration of phosphorus, potassium and ash than that of Myriophyllum spicatum, Potamogeton pectinatus and Spirodella polyrrhiza and reasonably the most preferred plant to Nile tilapia than others. Tender leaves of Myriophyllum spicatum were more preferable to tilapia because young leaves contained higher concentration of protein and mineral than does older leaves (Begon et al., 1997)

CONCLUSION
It is concluded that inclusion of Lemna meal into commercial diets would not significiantly affect feed quality and that duckweed meal may be a suitable protein source for practicial diets of channel catfish. The use of leafmeal as a possible fishmeal substitute is receiving increasing attention by fish nutritionists throughout world to 5 reduce feed cost (Bairagi et al., 2004). It is however important that the selectedplant sources do not conflict with the interests of human food security or their domestic animals (Amisah et al., 2009). Inclusion of such aquatic macrophytes as food and feed may serve dual purpose, i.e., bringing more plant derived foodstuff for aquaculture and making aquaculture more cost effective for farmers. Therefore, a combined effort comprising plant taxonomists, nutritionists, physiologists and fish culturists is warranted for making use of untapped potential of these macrophytes as feed for fish.