Variability in the routing of dietary proteins and lipids to consumer tissues influences tissue‐specific isotopic discrimination

Abstract

Mice used some fraction of their dietary lipid carbon to synthesize tissue proteins, suggesting flexibility in the routing of dietary macromolecules to consumer tissues based on dietary macromolecular availability. Consequently, all constituent dietary macromolecules, not just protein, should be considered when determining the relationship between diets and consumer tissues using SIA. In addition, in cases where animals consume diets with high lipid contents, non lipid-extracted prey samples should be analyzed to estimate diets using SIA.

Assimilation and isotopic discrimination of hydrogen in tilapia: implications for studying animal diet with δ2H

“…, Wolf et al. ), which our data show can be synthesized with hydrogen from non‐protein dietary macromolecules, even at modest dietary protein contents (~10%). Furthermore, in situations where animals consume diets deficient in protein, gut microbiota can even synthesize essential amino acids from non‐protein dietary macromolecules, which are ultimately assimilated by their host and used to synthesize tissues (Newsome et al.…”

“…, Wolf et al. ). Since lipids have much lower δ 2 H values than associated proteins, incorporation of lipid‐derived hydrogen into consumer tissues could affect δ 2 H‐based estimates of diet composition.…”

“…Lipids represent a significant source hydrogen and carbon that can be used by consumers to synthesize non‐essential amino acids, which constitute ~60–75% of amino acids found in tissues commonly analyzed by ecologists (Wolf et al. ). Our recent study showed that carbon sourced from dietary lipids was used to build non‐essential amino acids found in the tissues of laboratory mice grown on diets containing ≥15% lipids (Newsome et al.…”

Expanding the Isotopic Toolbox: Applications of Hydrogen and Oxygen Stable Isotope Ratios to Food Web Studies

“…As this field advances, there may also be utility in considering the isotopic composition of lipids in dietary items. Lipid-derived H can likely be used by eukaryotes to synthesis non-essential amino acids and construct proteinacious tissues, which has been shown to occur for C in lab mice that are fed diets 10-40% lipid (by weight) (Newsome et al, 2014;Wolf et al, 2015). Nevertheless, lipid extraction is currently recommended to maximize accuracy of δ 2 H measurements and mixing model outputs.…”

Growth rate and stable carbon and nitrogen isotope trophic discrimination factors of lion and leopard whiskers

“…The issue of lipid‐extracting dietary sources has been addressed differently among ecologists over the years. Experiments on the estimation of tissue‐diet TDFs are advised to first assess the lipid content of prey sources as automatic removal of lipids might result in unreliable estimates if animals consume lipid‐rich diets, since lipids are typically 13 C‐depleted compared with other macronutrients . Another major concern is the use of chloroform/methanol solution to extract lipids as the chemical can cause 15 N fractionation of 0.3–2.5 ‰ .…”