Abstract
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.
Highlights
Dietary lipid cannot be replaced by other nutrients because it plays important biological functions, and serve as a major source of essential fatty acid and provide energy [1]
The final body weight (FBW) and body weight gain (BWG) in fish fed 50% Palm oil (PO) diet was significantly higher than in 25% PO but was non-significantly different from other groups (P
The higher growth rate coupled with lower Feed conversion ratio (FCR) recorded in fish fed 50% suggested that 50% PO inclusion could maintain normal physiological functions for O. niloticus
Summary
Dietary lipid cannot be replaced by other nutrients because it plays important biological functions, and serve as a major source of essential fatty acid and provide energy [1]. Fish oil has traditionally been used as the major lipid component in fish feed [2] to provide essential polyunsaturated fatty acid (PUFA), especially highly unsaturated fatty acid (HUFA) [3]. Vegetable oils (VO) are potential and suitable candidates to replace fish oils in aquaculture feeds [5] because they have relatively considerable output, acceptable price, relatively low organic contaminant status and relatively high content of unsaturated fatty acids. Lysozyme is a lytic protein that is important in the non-specific defense system. Serum proteins are the most important compounds in the serum, with albumin and globulin being the major serum proteins [9] and are used to predict the general well-being of organisms including fish
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