Effects of fiber in supplemental feeds on milkfish (Chanos chanos Forsskal) production in brackishwater ponds

The study explores the nutritive value of fiber in supplemental feeds for milkfish. The feeding rates were adjusted so that all treatments involved equal protein-N load (6 g·kg-1 fish/day), and varying energy and fiber loads. Rice hull provided the bulk of dietary fiber. Fresh chicken manure, containing 16% protein, served as control. Four 800-m2 earthen ponds divided into four compartments were used. Milkfish juveniles (29 g) were stocked at 7,000·ha-1. After three months of culture, milkfish growth and production and protein efficiency ratio were significantly higher (α = 0.05) in fed ponds than in manured ponds. Average yield and manure conversion ratio in manured ponds were 436 kg·ha-1 and 14.5, respectively. There was no significant difference in yields (600-624 kg·ha-1) between feed treatments. Fish exposed to low protein/33% fiber diet had a worse feed conversion ratio (5.8) than those exposed to high protein/15 or 24% fiber diets (3.6). The results indicate that energy was not limiting in the high fiber (24%) treatment compared to low fiber (15%), but additional fiber (33%) did not further improve growth; and fiber in low protein diets was utilized further as a direct or indirect source of energy. Thus, a low protein/high fiber diet can be an economical way of increasing milkfish production in brackishwater ponds