Effect of ration level and dietary docosahexaenoic acid content on the requirements for long-chain polyunsaturated fatty acids by juvenile barramundi

Effect of ration level and dietary docosahexaenoic acid content on the requirements for long-chain polyunsaturated fatty acids by juvenile barramundi (Lates calcarifer), Aquaculture, 433, pp. 164-172. 1 Title: Effect of ration level and dietary eicosapentaenoic acid content on the requirements for docosahexaenoic acid by juvenile barramundi (Lates calcarifer). Abstract 27 Juvenile barramundi were fed one of six diets containing differing docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) levels. Fish were fed on a pair-fed feeding regime to eliminate variability in feed intake, with two diets fed to satiety to examine the effects of fixed or variable feed 30 rations on EFA requirements. Weight gain, feed intake, feed utilisation, and physical clinical signs were monitored. No effect of dietary DHA and EPA concentration, DHA:EPA ratio or total LC-PUFA level was observed on weight gain, growth rate, feed conversion ratio (FCR), survival or 33 physical clinical health signs. Satiety fed fish had higher feed intake, final weight, weight gain and growth rate compared to their respective restrictively fed treatments (P<0.05). No effect of ration level on the responses to DHA concentration was observed. Body fatty acid composition was affected 36 by diet, increasing dietary DHA resulted in higher body tissue DHA concentration, and a similar relationship was observed for EPA. Plasma haemoglobin increased with increasing DHA+EPA levels (P<0.05) while glutamate dehydrogenase increased for fish fed DHA+EPA in a 1:1 ratio, regardless 39 of total dietary LC-PUFA (P<0.05). Juvenile barramundi may be fed diets containing as low as 1 g kg-1 DHA without compromising growth or health status. 42 3 1.1 Introduction Traditionally, commercial aquaculture diets have relied on marine fishery oils for their lipid 45 component as they were readily available, competitive in price and contained the essential fatty acids required by fish (reviewed by Turchini et al., 2009). Increasing aquaculture production continues to place demands on static global wild fish resources, making their continued use unsustainable (Tacon 48 & Metian, 2008). To meet global aquaculture demands, a number of alternative lipid resources have been trialled including vegetable oils (such as palm oil, soybean oil, canola oil and rapeseed oil) and animal fats (such as lard, poultry oil and tallow; Turchini et al., 2009). However, all of these 51 alternative lipid sources are non-marine and lack long-chain polyunsatured fatty acids (LC-PUFA). Some freshwater species have little or no requirement for dietary LC-PUFA. However, the majority of 54 aquatic marine species have a …