Natural Stable Isotopes for Determination of Gastrointestinal Transit Time in Fish

Abstract

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.

Optimizing methodological aspects of stool collection by sedimentation in digestibility studies with pirarucu ( Arapaima gigas )

“…The greater amount of faeces produced around 5–9 h after the first feeding (8 h 00 min) shows that the second feeding (13 h 00 min) stimulated the transit of the digesta through the digestive tract, as reported by Braga et al (2007). Most GIT studies assess the flow of food after a single daily feeding (Braga et al, 2007; Dias‐Koberstein et al, 2005; Heng et al, 2007; Sandre et al, 2016); however, the present study provided two meals to maintain the dietary routine used in digestibility tests with juvenile pirarucu, with an aim of ensuring the applicability of the results of this type of experimentation. In addition, the amount of stool produced during the day was equal to the amount produced at night, which is advantageous, since it allows setting up a feeding and collection schedule throughout the day, especially after the second feeding of the day, when the stool production of the fish peaks.…”

The prospects of poop: a review of past achievements and future possibilities in faecal isotope analysis

“…While there have been numerous studies that use isotopes to investigate gut passage rates in different types of organisms (e.g. Südekum et al ., 1995; Warner et al ., 2014; de Sandre et al ., 2016; Botteon et al ., 2019; Gilannejad et al ., 2019), because faeces also contain tissues that take time to form (e.g. epithelial cells), gut passage rate and faecal isotope turnover may not operate on the same timescale.…”

Isotopic Discrimination and Persistence of the 13C Marker in Adults of Anastrepha fraterculus (Diptera: Tephritidae) Brazilian-1 Morphotype

“…The turnover of carbon after switching from a C 4 to C 3 diet and from a C 3 to C 4 diet was successfully described by the Boltzman model (Table 4). This model has been used to describe isotopic turnover in several tissue types and animal species (Balesdent & Mariotti 1996;Silva et al 2007;Martínez del Rio et al 2009;Ducatti et al 2014;Sandre et al 2016), but it did not fit the data from treatments with the Gainesville diet. Because the δ 13 C values of flies fed on this diet remained between −19‰ and −22‰ even after diet switching, the half-life could not be estimated.…”