Replacement of fish oil by poultry oil and canola oil in yellowtail kingfish (Seriola lalandi) at optimal and suboptimal temperatures

Abstract

Fish oil has been replaced by alternative oils to reduce the cost of aquaculture diets, but fish growth may be compromised when fish are fed these oils at suboptimal temperatures. A 5-week feeding trial was conducted to examine the interactive effects of water temperature and the partial or total replacement of fish oil with poultry oil and canola oil on the performance of yellowtail kingfish (YTK, Seriola lalandi), in the early stages of the production cycle. Practical diets were identical in composition, except the dietary lipid component was supplemented with 100% lipid as either poultry oil (PO), canola oil (CO), a blend of fish oil and poultry oil (FO/PO; 50:50) or a blend of fish oil and canola oil (FO/CO; 50:50). A control diet was included and the dietary lipid component contained 100% fish oil (FO). Fish fed the CO diet at 18°C had inferior growth performance, feed efficiency and nutrient retention, and showed higher incidences of green liver and lower plasma cholesterol levels than those fed the other diets. Whole body proximate composition was influenced by water temperature, but not diet, except moisture content which was highest in fish fed CO. The fatty acid composition of fillet lipid correlated with the PO and CO inclusion, in that the proportions of 18:1n-9, 18:2n-6 and 18:3n-6 all increased with increasing dietary PO and CO. The concentrations of 20:5n-3, 22:6n-3 and 20:4n-6 in the fillet lipid were reduced with increasing contents of dietary PO and CO. Our results confirmed that 100% poultry oil and 50% canola oil can replace fish oil in diets without reducing growth, but 100% canola oil results in poor fish growth compared with the FO control, regardless of water temperature. These findings are useful in dietary formulation to reduce feed costs without compromising yellowtail kingfish growth.