Lipid and Fatty Acid Requirements of Tilapias

Tilapias have been shown to have a dietary requirement for linoleic (n-6) series fatty acids (FAs; 18:2[n-6] or 20:4[n-6]). The optimum dietary levels of n-6 previously reported were 0.5% for redbelly tilapia Tilapia zillii and 1.0% for Nile tilapia Oreochromis niloticus. Tilapias may also have a requirement for the linolenic (n-3) FA series (18:3[n-3], 20:5[n-3], or 22:6[n-3]), but the optimum dietary requirement levels for n-3 in various tilapia species have not been determined. The presence of high levels of either n-6 or n-3 may spare the requirement of the other, although n-6 appears to have a better growth-promoting effect than n-3. Tilapias possess the ability to desaturate and chain elongate 18:2(n-6) to 20:4(n-6) and 18:3(n-3) to 20:5(n-3) and 22:6(n-3). Plant oils that are rich in n-6, n-3, or both FA series (e.g., soybean oil, corn oil, sunflower oil, palm oil products, and linseed oil) have been reported to be good lipid sources for tilapia. Beef tallow and pork lard are poorly utilized by tilapia. However, these lipids can be used in combination with other lipid sources provided that the essential FA requirements are met. Information on the nutritional value of fish oil for tilapias is inconsistent. Some studies have shown that the nutritional value of fish oil is similar to that of plant oils, while others have reported poor performance of diets that contain fish oil. Fish oil provided good spawning performance for tilapia broodstock reared in brackish water, whereas soybean oil yielded good reproductive performance in freshwater. The sparing effect of dietary lipids on protein utilization has also been demonstrated. However, tilapias do not tolerate as high a dietary lipid level as do salmonids. A dietary lipid level of 5-12% has been suggested as optimum in diets for tilapias.