| Summary: | 碩士 === 國立宜蘭大學 === 動物科技學系碩士班 === 100 === The primarily ingredient of protein used in aquaculture is the fishmeal. However, the finite nature of valuable fishmeal, combined with increased overfishing and pollution in the oceans, has raised concerns regarding the alternative protein to replace fishmeal. Furthermore, for the sake of sustainable development of aquaculture, the industry should shift to a more environmental-friendly or organically produced operations. To meet the demands of rapidly expanding organic sectors (organic agriculture in general), any alternatives to substitute fishmeal are regarded as a priority. Earthworms contain sufficient protein to make them suitable as food for animals, as their amino acid profiles are similar to those of other chemical constituents in the body. Hence, earthworm possess a considerable potential for developing organic aquaculture which combine both vermiculture (earthworm culture) and aquaculture.
The present study aimed to evaluate using earthworms as the alternative source of protein or diets in aquaculture feeds. The most widely produced species of crustacean farming in Taiwan i.e. giant freshwater prawn (Macrobrachium rosenbergii) in freshwater aquaculture and white shrimp (Litopenaeus vannamei) in marine aquaculture respectively were chosen for the study. The experiments for the growth performance in giant freshwater prawn were conducted separately with the male and female groups due to their phenotypic difference between males and females (sexual dimorphism). The feeding regime for the male giant freshwater prawn fed three times a day at a daily feeding rate of 2.5% biomass as follows: all commercial shrimp pellets, all live earthworms, and once each day with pellets and earthworms feeding respectively. The results showed that no significant differences was found in SGR between the treatments (p> 0.05) at male groups, while the groups fed with earthworms possessed the least feeding effect (higher FCR 17.4±10.2). The trials for the female giant freshwater prawn only fed with commercial shrimp pellets and live earthworms respectively. Similarly no significant differences was found in SGR between the treatments fed with pellets and earthworms at female groups, while the groups fed with commercial pellets possessed a better FCR.
Four trials were conducted in the white shrimp groups fed at 5% biomass lasted for 8 to 14 weeks. The first trial for white shrimp fed twice daily with commercial shrimp pellets and live earthworms respectively. The second trial for white shrimp fed as follows: all commercial shrimp pellets, all live earthworms, and once each day fed with pellets and worms respectively in the morning or afternoon. The results of two trials showed that no significant differences were found in SGR between the treatments (p> 0.05), while the groups fed with commercial pellets possessed a better (lower) FCR than those fed with earthworms. The third trial was conducted in a three-dimensional aquarium system, fed with commercial shrimp pellets, live earthworms and frozen earthworms respectively. The result showed that SGR of fed frozen earthworms was the worst, while the groups fed with commercial pellets possessed a better (lower) FCR than those fed with earthworms. The fourth trial was conducted in four outdoor tanks to mimic the business model and two of them fed with commercial shrimp pellets and another two tanks fed frozen earthworms. Regardless of SGR or FCR, the groups fed with commercial pellets possessed better growth performance than those fed with earthworms (p< 0.05).
The sensory evaluation test were also taken in the end of the experiment respectively in the giant freshwater prawn and the second trial of white shrimp group as the consumer’s acceptance of shrimp meat fed on worm meat is crucial to its application. Although the sensory evaluation of the shrimp fed on worm meat was slightly worse, but compared with those fed commercial pellets, there were no significant differences on juicy and texture (p>0.05).
The preliminary study indicated that the earthworms can be a good candidate as an alternative aquaculture feeds in response to the environmental deterioration following by the shortage of fish meal supply in the future. Hence, the earthworm should deserve more attention and should also be given more emphasis on the related research.
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