Taurine: A Critical Nutrient for Future Fish Feeds
2015-05-04 16:52:07   copyfrom:thefishsite    hits:

The amino acid taurine is a crucial ingredient in the diet of many commercially important fish species, but the removal of fishmeal from diets may cause a deficiency, write Guillaume Salze and Allen Davis from Auburn University.
Taurine (2-aminoethanesulfonic acid) is an organic acid which was first described from ox bile. In recent years, a number of studies have demonstrated the essentiality of dietary taurine for commercially relevant species such as marine teleosts.
Taurine is involved in bile salt formation, membrane stability, immunomodulation, anti-oxidation and mitochondrial function, and calcium-signaling.
Consequently, the removal of taurine-rich dietary ingredients such as fishmeal may create a deficiency, of which symptoms include reduced growth and survival, increased susceptibility to diseases, and impaired larval development.
Although the supplementation of taurine will be necessary to further reduce the use of ingredients such as fishmeal, taurine is not currently approved by the FDA in the USA for fish feeds. Obtaining approval in the United States to utilize taurine in fish feeds could improve the environmental and economic sustainability of fish feeds.
Taurine exists naturally in animals including mammals, birds, fish, and aquatic invertebrates such as oysters and mussels. Although plants contain less than 1% of the taurine levels found in animals, the most taurine-rich plants are algae, followed by fungi and other terrestrial plants.
High taurine levels naturally occur in seafood and meat, and many vertebrates can synthesize taurine. On the other hand, certain animals, including species containing high levels of taurine, cannot metabolically synthesize taurine and require dietary sources for physiological processes.
Approximately 5000–6000 tons of taurine (synthetic and purified from natural sources) were produced in the world in 1993, and were divided at 50% for pet food manufacturing, and 50% for pharmaceutical applications.
An updated global production is difficult to estimate and would require a full market analysis. However, there is no doubt that today’s production is considerably higher than it was in 1993.
Currently, global taurine production is destined to three main uses: cat food, infant formulas and the beverage industry for “energy” drinks. According to manufacturers, taurine products are crystalline powders more than 98.5% pure and conform to standards of the United States, Japan, and Europe.
To our knowledge, all products are based on the 98.5% purity level, hence there is no food or feed grade taurine. Taurine can be produced either by extraction and purification from taurine-rich sources or by chemical synthesis.
The majority of taurine is produced by chemical synthesis because extraction is less efficient, more costly, and initial materials (e.g., bovine or ovine bile) are not available in sufficient amounts to meet the global market demand.
Novel methods include the genetic modification of prokaryote or eukaryote cells to increase taurine biosynthesis. However taurine produced by such methods is not currently available commercially.
April 2015

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