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Five isolipidic experimental diets (32% crude protein) were formulated to contain 3% fish oil (FO) and virgin coconut oil (3VCO) as sole lipids or blends of FO + VCO in ratios of 75:25% (0.75VCO), 50:50% (1.5VCO) and 25:75% (2.25VCO). Triplicate groups of O. niloticus were fed one of five diets to apparent satiation, twice daily for 8 weeks. It was observed that fish fed diet 3VCO exhibited the best performance with respect to feed intake (492.1 g), final weight (214.60 g) and weight gain (154.90 g). Significant effects of dietary fatty acid profile were reflected in fish fed the diets in whole body, muscle and liver C12:0 and C14:0. However, eicosapentaenoic (EPA, 20:5n-3) and docosahexaenoic (DHA, 22:6n-3) were significantly different (P ! 0.05) compared to their respective diets while liver n-3: n-6 ratio significantly increased and recorded low levels in whole body and muscle. Statistically, least values of mortality were recorded as VCO levels were elevated when fish were subjected to Streptococcus iniae infection while plasma metabolite indicators among treatments were not altered. The inclusion of VCO at 3% in the diet gave excellent performance, indicating that it could wholly replace FO and as such represents a better alternative lipid source for feeding O. niloticus.

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This study was conducted to investigate the effects of replacing dietary fish oil (FO) with palm oil (PO) in juvenile Nile tilapia, Oreochromis niloticus (9.34± 0.02g initial weight) with emphasis on growth performance, digestive enzyme activities as well as serum biochemical parameters. Also, lysozyme activity (LYZ), respiratory burst (RB), superoxide dismutase (SOD), catalase (CAT) and resistance to Streptococcus iniae were investigated. Fish were stocked in 15 rectangular fiber glass tanks (150× 60× 40 cm) at 40 fish per tank with water maintained at 210 litres. Fish were fed five isonitrogenous (33% crude protein) and isolipidic (10% lipid) diets with PO included at 0% (0% PO), 25% (25% PO), 50% (50%PO), 75% (75% PO) and 100% (100% PO) for 8 weeks. The findings demonstrated that growth, and feed utilization was not compromised when PO was used in place of FO either partially or totally. Except for protease activity which was not significantly altered, lipase and amylase activities were significantly altered when FO was replaced with PO. There were no significant differences among treatments for CAT, SOD and LYZ. Serum malondialdehyde (MDA) in fish fed 100% PO was significantly lower than all other groups whiles total antioxidant capacity (TAC) of fish fed 0% PO was significantly higher than all other groups. Fish fed 0% PO, 25% PO and 50% PO had glutathione reductase (GR) significantly higher than fish fed 75% PO and 100% PO. RB in fish fed 0% PO were significantly lower than fish fed 75% PO and 100% PO. Also, fish fed 0% PO had significantly lower total protein (TP) compared with groups fed 50% PO and 75% PO. Fish fed diets with PO had similar resistance ability to Streptococcus iniae as those fed diets with FO. However, the liver function was likely to be compromised due to the increase in aspartate amino transferase (AST) and alkaline phosphatas (ALP) along increasing PO inclusion levels. AST, total protein, triacylglycerol (TAG) and low-density lipoprotein cholesterol (LDL-C) were significantly higher (p<0.05) in groups fed higher levels of PO. This study therefore concludes that feeding tilapia fingerlings with diets containing PO affects antioxidant and innate immune parameters negatively due to the reduction in LYS, TAC, GR, MDA, CAT, SOD and GSHpx.

This study was aimed at elucidating the effects of replacing fish oil (FO) with palm oil (PO) on tissue fatty acid composition, lipogenic enzyme activities and mRNA expression of genes related to lipid metabolism in Nile tilapia, Oreochromis niloticus (6.72± 0.14g). An eight week feeding trial was conducted using five isonitrogenous and isolipidic diets containing 0% PO, 25% PO, 50% PO, 75% PO and 100% PO. PO supplementation led to a significant increase in total saturated fatty acid (SFA), total mono unsaturated fatty acids (MUFA) and 18: 2n-6, whiles DHA, EPA, total n-3 as well as 20: 2n-6 were reduced significantly in the liver (P＜0.05). With the exception of glycerol-3-phosphate acyltransferase (GPAT) enzyme activity, supplementing tilapia diet with PO significantly increased fatty acid synthesase (FAS), acetyl-CoA carboxylase (ACC), steroyl-CoA desaturase 1 (SCD1), ATP citrate lyase (ACYL), carnitine palmitoyltransferase Ia (CPTIa) and carnitine palmitoyltransferase Ib (CPT Ib) (P＜0.05). In addition, significant/positive correlations were observed among dietary PO and/or liver tissue FA with FAS, ACC, SCD1 and ACYL mRNA expression while a negative correlation was recorded for CPTI mRNA expression. Generally, inclusion of PO in tilapia diets resulted in lipid accumulation in the liver and altered the key gene expression of lipid metabolism.