PROCEEDINGS | International Workshop on Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia 2014  Potential of Cowpea (Vigna unguiculata L.) Meal as an Alternative Protein Source in Diets for Giant Freshwater Prawn (Macrobrachium rosenbergii, de Man 1879) Frolan A. Aya a* , Maria Lourdes Cuvin-Aralar a and Relicardo M. Coloso b a Binangonan Freshwater Station, Southeast Asian Fisheries Development Center, Aquaculture Department, Binangonan, Rizal 1940 Philippines b Tigbauan Main Station, Southeast Asian Fisheries Development Center, Aquaculture Department, Tigbauan 5021, Iloilo, Philippines * faya@seafdec.org.ph Abstract Growth trials were conducted to evaluate cowpea Vigna unguiculata (L.) meal as a potential protein source in diets for giant freshwater prawn, Macrobrachium rosenbergii (de Man 1879), reared in tank and lake-based cages. Five isonitrogenous (approximately 37% crude protein) and isocaloric diets were formulated where fsh meal (FM) protein was replaced with 0%, 15%, 30%, 45% and 60% cowpea meal protein (or CP0, CP15, CP30, CP45, and CP60, respectively). Results of an 8-week tank trial showed that the fnal body weight (FBW), percent weight gain, specifc growth rate (SGR) and survival of prawns were not signifcantly infuenced by dietary treatments (P > 0.05), although the highest values, except for survival, were observed with CP45. In a lake- based cage trial that lasted for 16 weeks, prawns fed CP30 and CP45 had signifcantly higher FBW (13.1 and 14.4 g, respectively) compared to other treatment groups (P < 0.05). SGR (4.52–5.00%/ day), survival rates (53-77%), yield (98.5-116.5 g m-2) and feed conversion ratio (FCR; 2.0-2.7) were not afected by increasing levels of cowpea meal in the diets. Based on these results, cowpea meal can be considered as an alternative protein source in diets for M. rosenbergii. Keywords: Vigna unguiculata, giant freshwater prawn, growth, Laguna de Bay Introduction Te giant freshwater prawn (Macrobrachium rosenbergii de Man) is an economically important species for aquaculture in Asian countries such as China, India, Tailand and Malaysia. It is a promising alternative to black tiger shrimp (Penaeus monodon) due to its high market value and relatively low susceptibility to diseases. Presently, in the Philippines, farming of M. rosenbergii in natural inland water bodies such as lakes and reservoirs could be a sustainable option for the growth of aquaculture in lake-shore fsh farming communities (Cuvin-Aralar et al., 2007), similar to other well-known species such as bighead carp Aristichthys nobilis, milkfsh Chanos chanos and Nile tilapia Oreochromis niloticus. Farming of this species requires a nutritionally-balanced diet for optimal growth and survival. However, the rising cost of feed hinders proftability of production due to the use of