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A prized aquaculture commodity, the tropical
abalone Haliotis asinina has a high market demand in both local
and export markets. Because of this, researchers are trying to come up
with diet formulations that could support greater growth while
minimizing feed cost.
Abalones are herbivores in their natural
habitats, feeding mostly on macroalgae like seaweeds. In the culture
environment, however, experiments from Taiwan have noted that abalone
juveniles fed formulated diets had 65% greater growth than those fed
solely with macroalgae. In addition, they were found to contain
relatively higher protein content than the seaweed-fed abalone.
Formulated feed must contain sufficient
nutrients like protein and amino acids to encourage growth of H.
asinina. Palatability, digestibility and the presence of the right
balance of amino acids are important considerations in choosing the
protein source to be incorporated in the artificial diet.
The study conducted by Myrna Bautista-Teruel
and colleagues of SEAFDEC/AQD focused on the development of practical
diets for the abalone, with emphasis on the determination of suitable
protein sources such as fish meal, defatted soybean meal and the
blue-green alga Spirulina sp. for incorporation in the formulated
diets.
In their tests, the proponents prepared four
practical diets. Diet 1 consisted of either fishmeal (FM), shrimp meal
(SM) and defatted soybean meal (DSM) as the main protein sources. Diet 2
was composed of FM and DSM, Diet 3 was made up of DSM and SP, and Diet 4
consisted of FM, SM, and SP at 27%. These were then fed to abalone
juveniles under controlled environments.
Eighty-four days later, results showed Diet
2-fed abalone to have the highest weight gain of 453.8%. However, the
results were not significantly higher than those fed with Diet 4. Diet 3
registered lower weight gain, growth rates and length gains in abalone.
The results showed that a feed protein from a combination of plant and
animal sources promoted better growth rates than those prepared from
plant origins alone. One of the reasons cited for this is that Diet 3
had low levels of the essential amino acid methionine, which are found
in larger amounts from animal sources.
Since the reliance on animal-based feed
diets alone could prove expensive, combining them with plant-based
protein sources could strike the perfect balance between sustained
growth rates and minimal cost.
Read more of this article from the journal
Aquaculture (2003) 219: 645-653.
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