Leaching of taurine from commercial type aquaculture feeds

Leaching of soluble compounds from pelleted feeds is an issue for the aquaculture industry through increased environmental impact and reduced ingestion essential components. This study was undertaken to examine the leaching rates of taurine, a non-protein amino acid with critical physiological roles in teleosts. To this end we adapted a new liquid chromatography mass spectrometry (LC-MS) method for quantifying taurine. Twelve different feeds (4mm dia.) varying in protein source and taurine levels were examined. Fishmeal content ranged from 0.0% to 45.5% with taurine supplementation ranging from 0.0% to 5.0%. Taurine was extracted and quantified from individual pellets in triplicate at six time points (0, 1, 5, 10, 20 and 40min). Leaching rates ranged from 0.026 +/- 0.005 to 0.826 +/- 0.121mgmin(-1) over 40min at 27 degrees C and were strongly correlated to initial taurine content of the feeds (for distilled water n=12, P<0.001, R-2=0.91 for artificial seawater, 25 ppt, n=4, P=0.020, R-2=0.96). Loss of taurine from feeds was 59.5 +/- 16.5% after 40min. This study shows that a significant amount of taurine is lost over time from uneaten feed and that taurine supplementation should exceed requirement levels for slow consumers or feed being delivered as multiple additions.