Investigations on the nutrient and antinutrient content of typical plants used as fish feed in small scale aquaculture in the mountainous regions of Northern Vietnam

The aquaculture system of the Black Thai farmers in the upland of Northern Vietnam mostly depends on green leaves which they use as major feed input to the ponds. A study was conducted to assess the quality of two groups of plant residues used as fish feed (principally for grass carp) in Northern Vietnam. The first group was constituted of residues commonly fed to fish, such as cassava (Manihot esculenta), banana (Musa nana), and bamboo (Bambusa vulgaris) leaves, and the second group included residues occasionally fed to fish by farmers, such as barnyard grass (Echinochloa erusgalli), mixed weeds from paddy fields, Elephant grass (Pennisetum purpureum), mulberry (Morus), maize (Zea mays), sweet potato (Ipomoea batatas), peanut (Arachis hypogaea); cassava tubercles and crop residues such as rice bran, cassava peels. In the first group of plant material analysed any possible temporal changes in their nutrient, energy and antinutrient contents during the course of the year were evaluated, whereas in the second group the nutrient, energy and antinutrient content were determined, without any evaluation of their temporal changes. No significant temporal changes were observed in the proximate composition, energy and antinutrient contents of banana leaves during the course of the year. Significant (P<0.05) temporal changes were observed in the proximate composition of cassava and bamboo leaves as well as in the content of some antinutrient of cassava leaves. Results of proximate analysis indicated the high potential of some of these plant materials such as cassava and mulberry leaves as fish feed because of their higher protein and energy content. However, the protein and energy content of these leaves were generally very low when compared to that of the common standard fish feed. Thus, these plant feedstuffs alone may not be sufficient to cover the requirements for rapid growth in cultured grass carp. The data presented here could be used for formulating cost-effective and balanced animal feeds for the use of small-scale farmers in rural areas in Northern Vietnam.