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Natural Stable Isotopes for Determination of Gastrointestinal Transit Time in Fish

de Sandre, Lidiane Cristina Gonçalves, Buzollo, Hellen, do Nascimento, Thiago Matias Torres, Neira, Lígia Maria, Abimorad, Eduardo Gianini, Jomori, Rosangela Kiyoko, Ducatti, Carlos, Portella, Maria Célia, Carneiro, Dalton José
Journal of the World Aquaculture Society 2016 v.47 no.1 pp. 113-122
C4 plants, Piaractus mesopotamicus, carbon, chromic oxide, color, diet, feces, feeding methods, fish, gastrointestinal transit, ingredients, juveniles, metabolism, rearing, stable isotopes, tanks, temperature, titanium, titanium dioxide
This study evaluated the application of stable isotopes of carbon as an alternative and more accurate method to determine gastrointestinal transit time (GTT) in fish by comparing it to the inert marker method. The stable isotope method detects alterations of the normal carbon flow in a biological system by analyzing naturally occurring isotopes of carbon, contrary to studies based on conventional techniques that apply external markers to the diet to determine GTT through visual observation of the color change in feces. Therefore, 320 pacu, Piaractus mesopotamicus juveniles were reared in 32 tanks under two different temperatures (25 and 29 C). The pacu juveniles received two different diets, one based on ingredients derived from C₃ photosynthetic cycle plants and the other based on C₄ plant ingredients, both containing titanium oxide (TiO₂) as a marker. After 40 d, the isotopic signature of the diets was changed, and the marker was replaced by chromic oxide (Cr₂O₃). In the isotopic technique, the feces were analyzed to determine the exchange in the isotopic ratio of carbon δ¹³C. Both methods found that GTT was faster (nearly 6 h) in fish at 29 C when using the C₄/C₃ feeding strategy and slower in fish at 25 C using the C₃/C₄ strategy (15 h by inert marker and 18 h by the isotopic method). In conclusion, GTT determination in pacu juveniles using the stable isotope technique exhibits the same accuracy obtained with the inert marker method at temperatures suitable (nearly 29 C) for the metabolism of these animals.