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Abalone, being herbivores, are known to feed
on seaweeds in the wild. However, seaweeds like Graciliariopsis
bailinae are economically important in themselves, being sources of
valuable agar. Seaweeds just can not be used as feed. Hence, locally
available plants may just be the right supplement or replacement for
expensive components in formulated feeds for abalone.
In the Philippines, the terrestrial plants
Carica papaya, Leucaena leucocephala, Moringa oliefera,
locally known by their less-daunting names papaya, ipil-ipil,
and malunggay, respectively, may be the ideal candidates for this
purpose. A freshwater fern, Azolla pinnata, is another potential
alternative, being incorporated in the diets of tilapia and carp to
promote their growth.
A study conducted by SEAFDEC/AQD’s Ofelia
Reyes and Armando Fermin tests this idea. About 13% of the total 27%
crude protein of formulated diets come from the plant meals. The
formulated diets were fed daily to juvenile abalones stocked in fifteen
60-liter fiberglass tanks at 2-3% of their body weights, while the
control feed consisting of fresh Graciliariopsis bailinae was
given daily at 30% of the total body weight.
After 120 days, the results were in:
specific growth rates of abalone fed M. oliefera and A.
pinnata were significantly higher than those fed L. leucocephala,
but not to those fed fresh G. bailinae. In terms of weight, diets
based on M. olifiera, A. pinnata and fresh G. bailinae
showed greater gains compared with the L. leucocephala-based
diet. Abalone fed M. oliefera also had a significantly higher
protein productive value (PPV) of 79.9, while the rest had values 57.3
or lower, with that of G. bailinae having the lowest value of
only 12.3.
Why the results? The higher growth rate of
M. oliefera- and A. pinnata-fed abalone could be due to
the physical characteristics of the leaves, having softer textures and
less fiber compared to the other leaf meals. M. oliefera is also
rich in the minerals calcium, iron and phosphorous, which could have
improved the nutritive value of the diet. On the other hand, L.
leucocephala contains the anti-nutritional factor mimosine, which
could still have been present in the diet. This explains why abalone fed
this treatment had the lowest weight and length gains.
Given that one of the main concerns in the
culture of abalone is the high cost of feed, it would not hurt if the
commonly-found M. oliefera and A. pinnata be used as one
of the ingredients of diets for abalone. Not only are they available
year-round, they also contain essential nutrients to support the growth
of H. asinina.
Read more from the journal Aquaculture Research (2003)
34: 593-599.
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