Abstract
BackgroundDue to the continuous demand for fish coupled with decline in capture fisheries, there is the need to increase aquaculture production to meet the demand. Aquaculture is faced with high cost of feeding since fish oil and fish meal are expensive. In view of this, there are calls to explore alternatives that are cheap and reliable.ObjectivesThis study on Oreochromis niloticus was conducted to evaluate the effects of replacing fish oil (FO) with palm oil (PO) at 0%, 25%, 50%, 75%, and 100% on muscle fatty acid and proximate composition as well as growth-related enzyme activities and mRNA expression.MethodsOreochromis niloticus were fed five experimental diets (33% crude protein and 10% crude lipid) for 8 weeks. Feed had variation in fish oil and palm oil contents. After the 8 weeks feeding trial, five fish were sampled from each tank (15 from each treatment) and euthanized using an excess dose of tricaine methane sulfonate (MS-222 at 200 mg/L). Fatty acid and enzyme activities were analyzed using standard protocols. Also, RT-qPCR was used to quantify the expression levels of selected growth-related genes.ResultsFish fed 25% PO recorded the least muscle protein content and was significantly lower than the group fed 100% PO. Paired box protein 7 (Pax-7) enzyme activity was significantly higher in the group fed 50% PO compared to the groups fed 25% PO and 100% PO, while caplain-3 (Capn-3) was significantly lower in the group fed 0% PO compared to all other groups. There was a significant difference among treatments with respect to mRNA expression of Pax-7 and Capn-3. Group fed 25% PO had significantly lower mRNA expression of Pax-7, while the group fed 75% PO recorded significantly higher mRNA expression of Capn-3 compared to groups fed 0% PO, 25% PO, and 100% PO. Pearson’s correlation analysis revealed that Igf-I and Igf-II mRNA expression have significant correlation with n-3 polyunsaturated fatty acids content in muscle.ConclusionThe results suggest muscle protein content could be modified if FO is replaced with PO. Also, mRNA expression of Pax-7 and Capn-3 is affected by replacing FO with PO.
Highlights
Dietary vegetable oils are used as feeding material to replace the fish oil due to their abundance and relatively cheaper prices
Paired box protein 7 (Pax-7) enzyme activity was significantly higher in the group fed 50% palm oil (PO) compared to the groups fed 25% PO and 100% PO, while caplain-3 (Capn-3) was significantly lower in the group fed 0% PO compared to all other groups
The results suggest muscle protein content could be modified if fish oil (FO) is replaced with PO
Summary
Dietary vegetable oils are used as feeding material to replace the fish oil due to their abundance and relatively cheaper prices. Muscle growth is controlled by several genetic factors such as growth hormone (GH), insulin-like growth factors (Igfs), and paired box proteins (Paxs) (Johnston et al 2008). GH stimulates muscle growth in fish by inducing proliferation of myogenin cells and muscle hyperplasia and/or hypertrophy. Pax-7 gene is a powerful regulator of muscle progenitors and satellite cells that contributes to the proliferation of myogenic cells during the secondary myogenesis in fish. All of these genes act as a positive regulator of muscle growth that promotes hyperplasic and/or hypertrophic muscular growth. There are calls to explore alternatives that are cheap and reliable
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