February 15-18, 2009 Washington State Convention Center Seattle ...

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LIPID AND FATTY ACID REQUIREMENTS OF TILAPIA
Chhorn Lim and Mediha Yildirim-Aksoy
Aquatic Animal Health Research Laboratory
USDA-ARS, MSA
Auburn, AL USA
Chhorn.lim@ars.usda.gov
Dietary lipids are an important source of highly digestible energy and are the only source of essential fatty acids required for
normal growth and development. They are also carriers and assist in the absorption of fat-soluble nutrients, such as sterols and
fat-soluble vitamins, serve as a source of phospholipids and participate in the synthesis of hormones, prostaglandins and other
metabolically active compounds. Tilapia have been reported to have a dietary requirement for linoleic (n-6) series of fatty acids.
The optimum dietary levels of n-6 (18:2 n-6 or 20: 4 n-6) have been estimated to be 0.5 and 1% for redbelly tilapia (Tilapia
zillii) and Nile tilapia (Oreochromis niloticus), respectively. This information for other species has not been determined, but it
has been suggested that blue tilapia (O. aureus) have a relatively high requirement for n-6 fatty acid. Tilapia may also have a
requirement for linolenic (n-3) series of fatty acids. However, the optimum dietary requirement level for n-3 has 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
better growth promoting effect than n-3. Tilapia appear to 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.
Research evaluating various sources of dietary lipids showed that plant oils rich in n-6 and/or n-3 series of fatty acids, such as
soybean oil, corn oil, sunflower oil, palm oil products and linseed oil are good lipid sources for tilapia. Beef tallow is a poorly
utilized by tilapia when used as the sole lipid source. However, it can be used in combination with other lipid sources providing
that their essential fatty acid requirements are met. Information on the nutritional value of fish oil for tilapia is inconsistent.
Some studies have shown that the nutritional value of fish oil is similar to that of plant oils, while others reported poor performance
of fish oil-containing diets. Fish oil provided good spawning performance for tilapia broodstock reared in saline water,
while in freshwater, good reproductive performance was obtained with plant oil (soybean oil). The sparing effect of dietary
lipids on protein utilization has also been demonstrated. However, tilapia do not tolerate as high a dietary lipid level as do salmonids.
A dietary lipid level of 5 to 12% has been suggested to be optimum for tilapia.
The discrepancy between the results of various studies could be due to various factors such as species, fish sex and size, previous
dietary history, source and levels of dietary lipid, composition and nutrient content of experimental diets, feeding duration
and practices, and environmental conditions (salinity, temperature, etc.).