Assessment of dry matter and protein digestibilities of selected raw ingredients by discus fish (Symphysodonaequifasciata) using in vivo and in vitro methods |
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| Authors: | ASC CHONG R HASHIM & AB ALI |
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| Institution: | Aquaculture Research Group, School of Biological Sciences, Universiti Sains Malaysia, Penang, Malaysia |
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| Abstract: | The reliability of several in vitro steps as compared with the conventional in vivo method to determine the dry matter and protein digestibilities of several raw ingredient by discus juveniles was assessed. In vitro studies were conducted based on a 12-h digestion method and measurement of pH drop involving four different substrate–enzyme mixtures, namely the Lazo single enzyme, Hsu multi-enzyme, Saterlee multi-enzyme and discus extract enzyme system. Results from both methods showed that fishmeal was highly digestible in terms of dry matter (67.22–87.52%) and protein (76.8–91.18%). With the exception of poultry offal meal, findings also indicate that discus digests dry matter in feedstuffs of animal origin (fish meal and beef heart) more efficiently compared with plant materials (soybean and wheat meal) with no obvious trend observed for protein digestibility in any of the ingredients tested. Apparent digestibility coefficients of not less than 40% suggest that all the ingredients tested were potential ingredients for development of formulated feed for discus culture. A comparison between the different in vitro enzyme systems tested showed that the Saterlee method, which used commercial mammalian and bacterial enzymes, was best in terms of its ability to differentiate the digestibilities of the various ingredients and correlation ( r 2=0.85–0.90) with the in vivo results. The use of a crude enzyme extract from discus digestive tract also provided values consistent with in vivo and Saterlee in vitro methods ( r 2=0.72–0.87), indicating the potential and need for further investigation to develop a more accurate in vitro assay based on discus digestive enzymes. |
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| Keywords: | digestibility discus dry matter protein |
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