World Aquaculture Magazine -December 2021

WWW.WA S .ORG • WORLD AQUACULTURE • DECEMBER 2021 53 Energy can be provided by lipids, carbohydrates and proteins, but the goal is to adequately formulate diets to facilitate energy assimilation by fish and to spare amino acids from proteins and essential fatty acids from lipids at a competitive price. Another challenge is to formulate diets rich in essential nutrients for Nile tilapia because fish will reduce feed intake at cold suboptimal conditions. Dietary lipids play important roles in energy provision, are source of essential fatty acids and regulate lipid metabolism and other physiological processes associated with the maintenance of fish health (Tocher 2003). Nutritional requirements of Nile tilapia have been studied extensively and are well understood. However, although dietary protein-to-energy ratio or amino acid profile information are widely known and valorized by fish producers, lipids and specifically ( C O N T I N U E D O N P A G E 5 4 ) tilapia production in subtropical regions. Studies carried out by the Fish Nutrition Lab (LABNUTRI) at the Federal University of Santa Catarina (UFSC, Brazil) since 2012 have demonstrated that proper lipid nutrition will improve the thermal tolerance of Nile tilapia in subtropical regions and has the potential to maintain growth during winter, decrease production costs and improve fillet quality. Lipid and Fatty Acids in Fish Nutrition The energy metabolism and feed intake of fish at cold temperatures is reduced (Zhou et al. 2019), but at the same time physiological processes are driven to accumulate body lipids, resulting in high levels of available energy during cold periods (Zhou et al. 2019). Therefore, increasing the concentration and digestibility of energy in commercial diets may improve cold tolerance in Nile tilapia. a. FIGURE 3. Nile tilapia farming in Brazil encompasses earthen ponds (a, mainly in Paraná state) as well as cage (b, mainly in São Paulo state) rearing systems. Feeding practices include manual (c) or automatic (d) feeders. Juveniles are reared in biofloc systems at high densities in Paraná state (e). b. c. d. e.