USE OF PLANT LEAVES AS FISH MEAL
Compiled & shared by-DR RAJESH KUMAR SINGH ,JAMSHEDPUR,JHARKHAND, INDIA, 9431309542,rajeshsinghvet@gmail.com
With the rapid growth in the aquaculture sector in the recent years, the demand for quality fish feed is continuously increasing. Providing quality fish feed became a prime aim of every aquaculturist. Though fish feed devours around 50% of the production cost, yet it plays the pivotal role in the production and yield outcome .With the increase in demand, the price of feed increased simultaneously. One main reason for the rise in the cost price of fish feed is due to the rise in demand of fish meal which remains the core of the protein supply of the feed. So, the quest for possible alternative protein sources to replace (complete/partial) fish meal in the feed became paramount . As animal protein sources are mostly expensive and not easily available, plant sources are considered to be one possible alternative that can be used in fish feed without compromising the nutritional quality of the feed. Moreover, use of cheaper and locally available plant sources to substitute the expensive fish meals would mean reduction in the production cost and thereby enhance the profit.
The prime consideration of selecting a fish feed ingredients and formulation of the feed is the digestibility, palatability and acceptability by the fish, availability and cost of the ingredients. Incorporation of plant sources in fish feed generally has its limitation due to low protein content, presences of anti-nutritional factors such as alkaloids, glycosides, oxalic acids, phytates, protease inhibitors, haematoglutinin, saponegin, momosine, cyanoglycosides etc. and their imbalances in some essential amino acids, fatty acids and micronutrients.
Use of alternative plant protein sources in fish feed————-
Plant products contain huge amount protein, different amino acid and fatty acids which are not available in animal protein. Use of plant protein in fish feed industry has been tried for various commercial culture fish species as the formulation of feed is specific to species based on their specific requirements. The advantages lie not only in the availability and economic benefits but also that these plant products also have less amount of phosphate and nitrogen than animal protein, therefore, reducing the chances of eutrophication of pond. Vhanalakar, reported that plant source feedstuffs suitable for fish feed formulation are pods, seeds, leaves, fruits of certain plants, grains, oilcakes like linseed, safflower, sunflower, soybean, roots, cereals and cereal by-products, broken rice, rice polish, tubers of sweet potato, wheat bran, maize, cassava, sorghum, etc. In fish feed industry Grasses, vegetables, aquatic weeds, plant’s leaves, stems, seeds and seed extracts are commonly used . Leaf meals for fish feed are often derived from plants of terrestrial as well as of aquatic origins.
1.Moringa leaf meal————-
The fresh leaves of Moringa oleifera or ‘drumstick’ are a highly nutritious supplement to the diet of plant-eating fish such as tilapia, barbs, fancy carps etc. . They harbor rich protein, lipids, vitamins and minerals and hence the leaves, kernel and pods are often used in aquaculture feed industry. Makkar reported that the leaves of this plant contain 23% crude protein while Egwui et al., suggested that drying, soaking and grounding the leaf meals into powder could reduce the antinutritional factors. The leaf is free from antinutritional factors except for saponins and phenols .Fresh Moringa leaves provide additional protein, vitamins and amino acid such as methionine, cystine, tryptophan that can improve the growth and health of fish . To partially replace conventional diets Moringa leaves has been successfully used without compromising the growth performance of Nile tilapia . They also reported that the optimum inclusion level of 20% moringa leaves can be used in the formulation diet for catfish C. gariepinus. Afuang and co-workers (2003) also reported that solvent extracts of moringa leaves can replace 30% of fish meal in O. niloticus diets. However, in contrast, Hlophe and Moyo reported that adding moringa leaf meals to diet of Tilapia rendalli even at the 25 % inclusion level was expensive and resulted in compromised growth and health which may be due to the presence of tannins and polyphenols. To substitute 10% of dietary protein steam heated moringa leaf meal can be used without a reduction in growth performance in Nile tilapia fry.
2.Subabul leaf meal ————-
Leucaena leucocephala, commonly called as ipil-ipil is a fast growing and droughtresistant tropical leguminous plant that is often used in the animal feed industry . The leaf contains more than 20% crude protein (on a dry matter basis) and seed has α-carotene with rich amino acid profile . However, its use has been limited due to the presence of a toxic, nonprotein amino acid, mimosine which retards the growth of animal when consume in high quantity . However, Pantastico and Baldia (1979) reported improved growth performances in tilapia on inclusion of leucaena leaf meal in diet. Leucaena is a good feed ingredient for small fishes such as mollies, topminnows (Poecilia spp.) and freshwater prawn. The inclusion of 33 to 100% leucaena leaf meal in the diet of Oreochromis niloticus fingerlings enhanced fish growth in the cages . Incorporation of L. leucaena leaf meal in the diets of O. niloticus at 12.5% inclusion did not affect growth, however, at high levels of inclusion, 25% or more, the growth was adversely affected . Moreover, Sotolu also revealed that the seed has high nutrient content with good protein source that enhanced the growth and survival of Clarias gariepinus.
3.Sweet potato leaves———-
Ipomoea batatas, sweet potato is widely culture around the world and is also one of the most important food crops in tropical areas . The leaves have been used as forage for the cattle due to high protein and fibre content . Preston (2006) also reported that the crude protein contents ranging from 26.5 to 32.5% in leaves of sweet potato. Adewolu (2008), in his review, mentioned that the leaf meal of the plant has 26-33% crude protein, high amino acid, mineral and vitamin content. He also cited that the advantage of using this plant meal in fish feed is because this plant leaves can be harvested many times a year thereby making the availability easier and cheaper. The presence of anti-nutritional factors such as invertase and protease inhibitors can be removed by oven or sun-drying, boiling or steaming and grinding prior to inclusion in fish feeds thereby increasing the palatability . Experiments on Tilapia zilli resulted that sweet potato leaf meal could be included up to 15% level in diets without compromising the growth and feed efficiency.
4.Mulberry leaf meal ————
Morus alba or mulberry leaves which are grown for silkworm industry is often used in fish feed formulations due to high protein content and mineral elements . The limitation of its use is due to deficiencies in essential amino acids, the presence of anti-nutritional factors and complex carbohydrates (NRC, 1993). Bairagi et al., (2002) recommended that fermentation could be a simple and cheap way to reduce the anti-nutritional factors in it. Mondal et al. reported that mulberry leaf meal could be a potential protein source in the diet of Labeo bata. Cruz and Laudencia used mulberry leaf meal for Nile tilapia resulting enhanced growth and lower FCR at 60% inclusion in combination with 40% rice bran. Bag et al., (2012) also reported this leaf meal incorporation in stinging catfish diet enhanced growth and survival, higher acceptance by fish and improved immunity against common disease.
5.Azolla———-
Mosquito plant or Azolla is an aquatic freefloating fern that has the ability to fix and assimilate atmospheric nitrogen. It grows rapidly and has the potential to double its weight in 2-3 days. It is also often referred to as “super plant” due to its high nutrient content such as essential amino acids, vitamins (vitamin A, vitamin B12 and BetaCarotene), growth promoter intermediaries and minerals like calcium, phosphorous, potassium, ferrous, copper, magnesium etc. Azolla contains high protein (19-31%) and low lignin which makes it a desirable ingredient in animal feed industry (Sheeno and Sahu, 2006). Azolla pinnata has been reported to be a potential protein source in fish feed industry (Micha et al., 1988). However, some researchers reported that feeding fresh or dried Azolla directly to the fish may result in poor growth (Antoine et al. gave an account of improved feed utilization in Tilapia mossambica and increased growth in Rohu, Nile tilapia, Common carp, Silver carp and Mrigal when Azolla is incorporated in the diet of the fish. Higher inclusion of Azolla protein concentrate beyond 50% reduced the protein utilization capacity in the diet of Labeo rohita fry (Sheeno and Sahu, 2006). Some researchers are in the view that Azolla powder should be used to replace only upto 25% fishmeal in tilapia (El-Sayeed, 1992), in Etroplus suratensis (Joseph et al., 1994), 45% in Cirrhinus mrigala fry (Gangdhar et al., 2014), 42% in Oreochromis niloticus fry (Santiago et al., 1988), respectively.
6.Water hyacinth
Water hyacinth, Eichhornia crassipes is a rapid growing, herbaceous, free-floating aquatic plant native to amazon basin. This plant is known to be “the world’s worst aquatic weed” due to their invasive nature and the culture of it is restricted in some part of the world. Lareo and Bressani (1982) reported that fresh and composted water hyacinth is used as feed for various animals. They reported 38% protein content in the dry matter of the leaves and 17-26% minerals. Use of water hyacinth as feedstuffs for fish diets for large scale was not recommended by many researchers unless the hyacinths are composted or fermented (Liang and Lovell, 1971; Wersal and Madsen, 2012). El-Sayed (2003) reported that fermented water hyacinth can be incorporated into the diet of Nile tilapia upto 25% inclusion level. He suggested fermentation to enhance the palatability and better utilization by the fish. Edwards and his co-workers (1985) also recommended composting of water hyacinth before incorporating into fish diet. They reported that composted water hyacinth can be used to replace fishmeal upto 75% replacement for diet of Nile tilapia. Saint-Paul et al (1981) revealed that inclusion of water hyacinth meal (dried and grounded) upto 18.9% inclusion level does not compromise the growth and survival of Matrincha fish. They, however, suggested that high-level inclusion may not be recommended as the presence of tannin in the plant interferes the protein digestibility.
7.Duckweeds
Duckweeds or water lens is a floating aquatic plant that grows luxuriantly in freshwater bodies in the tropical and subtropical areas (Majid, 1986). It consists of four genera viz. Lemna, Spirodela, Wolfilla and Wolffiella. Duckweeds (dry matter) contains 15-43% crude protein, 5-30% fibres, 5% lipids and often used in animal feed industry (Leng et al., 1995; Cheng and Stomp, 2009; Mohapatra and Patra, 2013). They also suggested use of duckweed in fish diet due to presence of high protein, trace minerals, K and P and pigments, particularly carotene and xanthophyll. Fresh duckweed has been successfully used as feedstuffs for common carp, Thai sharputi, raj puti, silver carp, mrigal and tilapia (Leng et al., 1995; Kabir et al., 2009). Mohapatra and Patra (2013) experimented on inclusion of duckweed in the diet of common carp. They arrived that fishmeal may not be replaceable by duckweed meal but can be used to supplement the diet upto 15% inclusion level to reduce the cost without compromising the growth. Das and Ray (1989) reported that dried duckweed (Lemna polyrhiza) could be potentially used as a feed ingredient for Labeo rohita fingerlings without affecting the growth and survival of the fish. Yilmaz et al., (2005) recommended fermentation of lemna leaf meal for fish feed formulation. They also reported that duckweed can substitute upto 20% of commercial fish meal in the feed of common carp. Fasakin et. al.,1999 outline that incorporation of solar-dried duckweed (Spirodela polyrrhiza) upto 30% fish meal replacement in diet of Nile tilapia enhance good growth and is cost effective. Mbagwu et al., (1990) reported that enhanced growth and survival of mango tilapia fingerlings fed with diet containing 10% duckweed (Lemna paucicostata)
