Growth, survival, and body composition of cage-cultured Nile Tilapia Oreochromis niloticus fed pelleted and unpelleted distillers grains with solubles in polyculture with freshwater prawn Macrobrachium rosenbergii

A 12-wk feeding trial was conducted in cages with juvenile Nile tilapia Ore ochromis niloticus to evaluate distillers grains with solubles (DDGS) as a direct feed, the effects of pelleting on its utilization, and the compatibi lity of caged tilapia and prawns in polyculture. Nine 1.0-m(3) cages were s tocked with 200 juvenile (26 +/- 0.9 g) tilapia. Cages were suspended in a 0.2-ha pond stocked with juvenile freshwater prawns Macrobrachium rosenberg ii at 40,000/ha. Three replicate cages were randomly assigned to each dieta ry treatment. In one dietary treatment DDGS was fed as an unpelleted loose grain ration (26% protein). In a second dietary treatment fish were fed DDG S that had been steam-pelleted (23% protein). Fish in a third dietary treat ment were fed a commercial catfish diet (31% protein) for comparison. After 12 wk, individual weight, individual length, and specific growth rate were significantly higher (P < 0.05) and feed conversion ratio was significantl y lower (P < 0.05) for fish fed the commercial catfish diet than for fish f ed either unpelleted or pelleted DDGS. Specific growth rate was significant ly higher (P < 0.05) for fish fed pelleted DDGS than for fish fed unpellete d DDGS. Survival did not differ significantly (P > 0.05) among treatments ( >95%). Although growth was increased in fish fed the commercial diet, their cost of production ($0.66/kg gain) was significantly higher (P < 0.05) tha n in fish fed unpelleted and pelleted DDGS ($0.26/kg gain and $0.37/kg gain , respectively). The costs of gain in fish fed unpelleted DDGS was signific antly lower (P < 0.05) than in fish fed the pelleted DDGS. Prawn production was 1,449 kg/ha and addition of tilapia in polyculture increased total pon d productivity approximately 81%. These data suggest that DDGS provides eco nomical growth in tilapia when fed as a direct feed and that polyculture of tilapia may improve overall pond efficiency in freshwater prawn production ponds, even at temperate latitudes.