Comparative digestion efficiencies in conventional, genetically improved and genetically male Nile tilapia, Oreochromis niloticus (L.).

摘要

Apparent digestibility of dry matter, protein, lipid and energy of a fishmeal-based feed (41% crude protein, 9% crude lipid and 19 kJ g-1 gross energy) was compared in genetically improved farmed tilapia (GIFT), genetically male Nile tilapia (GMNT) and conventional Nile tilapia (CNT) (Oreochromis niloticus). The experimental fish were reared individually under standardized conditions in a recirculation system at 27+or-0.1 degrees C for 10 weeks. Titanium dioxide (TiO2) was used as a marker. Faeces of individual fish were collected daily by siphoning and stored at -18 degrees C before analysis. No significant differences (P<0.05) were observed in the digestibility coefficients of feed dry matter (78.2+or-3.4%, 77.7+or-4.4% and 76.4+or-3.7%), protein (87.9+or-3.0%, 88.4+or-2.8% and 88.0+or-3.3%), lipid (90.0+or-2.5%, 91.0+or-2.1% and 89.4+or-3.0%) and energy (90.4+or-1.9%, 90.7+or-2.0% and 89.4+or-2.3%) in GIFT, GMNT and CNT respectively. At the end of the experiment, there were no significant differences (P<0.05) in average percentage growth (82.2+or-7.2, 87.3+or-7.7 and 74.7+or-4.1 respectively for GIFT, GMNT and CNT), growth rates or feed utilization efficiencies between the three tilapia groups. We conclude that the higher growth claimed for improved GIFT and GMNT as compared with CNT, if ever existing, cannot be attributed to higher nutrients or energy digestibility..