Mrigal (Cirrhinus mrigala), a carp endemic to Indo-Gangetic river systems, is one of the three Indian major carp species cultivated widely in Southeast Asian countries.
On a global
scale aquaculture is the fastest growing animal protein sector. However, many
fish require fish proteins in their diets and the availability is limited.
Nutritionists on a continuous basis are searching for alternatives to replace
the animal protein with plant protein. Indian researchers investigated the
possibilities of alfalfa meal in fish diets.
By S.A.
Vhanalakar and D.V. Muley, Maharashtra, India
Alfalfa
might be an interesting fishmeal substitute in fish feeds.
Fish meal
represents an ideal nutritional source of dietary protein and lipid for fish.
It is the most important protein source for the aquaculture industry because of
its high biological value, but this is a limited food resource and there is
serious concern about the long-term availability of this feed stuff for use in
fish diets.
The aquaculture industry depends worldwide on the availability of
low cost, high quality feed.
Over several decades, fish nutritionists have
evaluated alternative sources of plant origin protein in fish diets as partial
or total fishmeal replacement.
Good
nutrition in animal production systems is essential to economically produce a
healthy, high quality product.
In fish farming, nutrition is critical because
feed represents 40-50% of the production costs.
Fish nutrition has advanced
dramatically in recent years with the development of new, balanced commercial
diets that promote optimal fish growth and health.
The development of new
species-specific diet formulations supports the fish farming industry as it
expands to satisfy increasing demand for affordable, safe, and high-quality
products.
For
commercial culture of fish, the formulation of a low-cost balanced diet using
locally available agro-industry byproducts is needed. Recently fishmeal has
become the most expensive protein ingredient in aquaculture feeds.
Many
developing countries have realised that, in the long run, they will be unable
to afford fishmeal as a major protein source in aquafeeds.
Currently one of the
challenges that fish nutritionist face is to partially or totally replace
fishmeal with less expensive, non-traditional animal or plant protein sources.
Many studies have shown considerable success in partially replacing fishmeal
with soybean meal and other soybean products in the diet of various fish
species.
Research interest has been focused on different leaf meals as protein
sources in fish feed.
Fish nutritionists have evaluated alternative sources of
plant origin protein in fish diets as partial or total fishmeal replacement.
Alfalfa
meal
Alfalfa
(Medicago sativa) is a flowering plant in the pea family (Fabaceae), cultivated
as an important forage crop. In the United Kingdom, Australia and New Zealand
it is known as Lucerne and as Lucerne grass in south Asia.
Alfalfa is widely
grown throughout the world as forage for cattle due to its high protein
content.
In early Chinese medicines, physicians used young alfalfa leaves to
treat disorders related to the digestive tract and the kidneys.
Ayurvedic
physicians used the leaves for treating poor digestion. In an experiment, fresh
leaves of alfalfa plant were used in the formulation of fish feed.
Dried leaves
of alfafa in powder form were used for preparing fish feed. It was tested in
the diet of a freshwater fish, Cirrhinus mrigala (Mrigal carp) under laboratory
conditions.
The feeding experiment was carried out for three months.
The
various experimental diets contained different combinations of dry alfalfa leaf
meal, mixed with groundnut oil cake, rice bran, guar gum binder and a mineral
vitamin mixture
(Table 1).
Ingredients were mixed thoroughly in a kitchen mixer till a
homogenous mass was obtained.
With the help of a mincer, pellets were prepared,
which were immediately sun dried.
After drying, the pellets were hand broken up
into convenient pellet sizes and frozen until before feeding.
In this
experiment the alfalfa was incorporated at various percentage levels to check
the effectiveness as a fish feed ingredient. Medcago sativa solely does not
have the capacity to replace the traditional fish meal.
Therefore it is used as
a supplementary fish feed ingredient along with the traditional ingredients;
but the incorporation level of traditional ingredients like groundnut oilcake,
rice bran etc. was kept at a lower inclusion level.
Growth
performance on alfalfa diet
The growth
performance of Mrigal carp on the alfalfa diet is presented in Figure 1.
The
present study confirmed that Mrigal carp is able to utilise the plant based
formulated diet.
An inclusion level of up to 30% in the practical diet for
Mrigal carp fingerlings had no adverse effects on growth, feed utilisation
efficiencies or body composition of the fish.
From the present work it is
concluded that, Medicago sativa may be a promising source of plant protein;
used for partial replacement of fishmeal in the formulated fish feed.
It will
definitely help small scale fish farmers to cut costs on traditional fish feed.
S.A.
Vhanalakar works at the Department of Zoology, Karmaveer Hire Arts, Science,
Commerce and Education College. D.V. Muley works at the Department of Zoology
of the Shivaji University, both located in Maharashtra, India.
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