Effect of different dietary lipid sources on growth performance and nutrient utilization of + Nile tilapia (Oreochromis niloticus) fingerlings.

A feeding trial was carried out to investigate the use of plant oils in the feeding of Oreochromis niloticus fingerlings. Four iso-nitrogenous (30% crude protein) and iso-calorific (17 MJ kg-1 gross energy) diets including a fish oil control were formulated to contain 8%. A basal diet containing 100% FO was completely replaced by Soya oil, groundnut oil, and palm oil. A total of 120 O. niloticus fingerlings (1.20 ± 0.03 g, mean ± SE) were randomly allocated the diets after 7-day acclimation. There were 10 fish tank-1. Fish were hand-fed to apparent satiation twice for 63 days. The result obtained from the trial show that dietary supplementation of lipids significantly influenced growth performance and nutrient utilization of O. niloticus (P<0.05). The fish fed PO had the least weight gain (WG), final weight, protein efficiency ratio and highest compared to FO, SO and GO from d 7-28 (P><0.05). At d 35 the fish fed SO had the highest WG (P><0.05); no significant difference (P>0.05) in WG of fish fed FO, GO and PO diets was observed. The best weekly overall growth at the end of d 56 was in FO group; fish fed PO diet had the least WG, followed by GO. At d 63, WG of fish fed FO diets declined, while fish fed SO and PO diets showed a trend towards increase in growth. Result of ANOVA showed that there were significant differences (P<0.05) in FW (F=11.406, P=0.003), WG (F=11.428, P=0.003), FCR (F=7.274, P=0.011), and PER (F= 10.803, P=0.003) among the diets. At the end of the trial, the best growth in fish was recorded for FO group; however, there were no significant differences (P>0.05) in mean values of FW (P= 0.781), WG (P=0.999), SGR (P=0.991), PER (P=0.997), and FCR (P=0.879) between FO and SO-supplemented diets. The least WG was observed in fish fed PO diet followed by GO. Survival was 100% for all treatments. Whole body moisture and crude protein was least in PO group. FO had the highest (P<0.05) protein compared to all vegetable oils (VOs). However, whole-body protein of fish fed FO and SO were not significantly different (P>0.05). SO had the highest (P<0.5) lipid compared to FO, GO and PO. In conclusion, SO alone and a bend of PO and GO can be used as a alternative to FO without affecting growth performance of O. niloticus.

Water quality parameters analysed were within the requirement for Nile tilapia. While the partial replacement of FO with VOs did not affect growth and feed utilization in some fish species, in other species the total replacement of dietary FO with VOs significantly impacted negatively on growth and fillet quality resulting in growth retardation, abdominal and hepatic fat deposition.

Finally, experiments should be conducted to evaluate protein retention, nutrient utilisation and growth of Nile tilapia from fry to marketable size to evaluate the use of VOs in pond environment. The use of finishing diets in which FO is supplemented and fed to fish receiving VOs as wash-out should be evaluated to ensure the appropriate amount of EPA, DHA, and n-3/n-6 ratio are present in the final product for human health and well-being.

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