Stable isotopes for determining carbon turnover in sheep feces and blood

Abstract

a b s t r a c tThe objective of this work was to evaluate carbon turnover and half-life in feces and blood from sheep fed on C 3 and C 4 plant diets, using the stable isotope technique. Eight Santa Ines sheep were randomly distributed between two treatments: the first consisted of animals that were fed alfalfa hay, and the second consisted of animals that were fed corn silage only. Function of time was used to measure carbon turnover rate. At steady state, the half life for carbon isotopic enrichment between food and feces is 1.2 and 1.0 days for alfalfa hay and corn silage treatments, respectively. For blood data collection the time was insufficient to reach the isotope equilibrium level, indicating a slow carbon exchange between diet and blood. It is concluded that blood has a slow turnover, indicating the isotope signal for the former diets. Feces, by contrast, have a quick turnover, indicative of their recent diets.

Variations in stable isotope ratios in lamb blood fractions following dietary changes: a preliminary study

“…A comparison with other published studies is not possible, as data from Martins et al . pertained to δ 13 C values in whole blood, whereas Norman et al .…”

“…studied the variation in the integration time of dietary carbon in plasma and faeces in sheep fed with C3 or C4 plants for a period of 2–3 weeks. Martins et al . determined the half‐life of δ 13 C values in whole blood of lambs fed with leguminous plants or corn silage and found that the 167 days of the experiment were not sufficient to reach isotope equilibrium.…”

Diet‐tissue stable isotope (Δ13C and Δ15N) discrimination factors for multiple tissues from terrestrial reptiles

“…Consumer tissues generally contain more of the heavy isotopes of C and N than their food sources, thus leading to positive discrimination factors . However, excreta generally have lower δ 13 C values than their diets and their other tissues . It is not known exactly why this happens (see), but one hypothesis is that it is because the lighter isotope of carbon reacts more quickly than the heavier isotope, becoming more readily incorporated into waste products.…”

Stable isotope ratios of blood components and muscle to trace dietary changes in lambs

“…With regard to the comparison between animals fed exclusively pasture (P) or concentrate (S), all the studied isotopic ratios, d Smet et al, 2004;Norman et al, 2009;Martins et al, 2012). Table 4 Effect of the dietary treatment on the stable isotope ratios in erythrocytes and plasma of lambs fed pasture (P, 9 lambs), pasture followed by concentrates in stall for either 14 days (P-S14, 10 lambs) or 37 days (P-S37, 9 lambs) or concentrates in stall (S, 10 lambs)…”

“…These results disagree with Bahar et al (2009) who consider muscle to be an unsuitable tissue for detecting short-term pre-slaughter feeding changes in beef because of the long time required to reach isotopic equilibrium with a new diet. However, Martins et al (2012) Effect of the dietary treatment on the stable isotope ratios in defatted muscle and fat of lambs fed pasture (P, nine lambs), pasture followed by concentrates in stall for either 14 days (P-S14, 10 lambs) or 37 days (P-S37, nine lambs), or concentrates in stall (S, 10 lambs) found that even if the isotopic equilibrium in plasma was not reached after 104 days on the experimental diets, different isotopic ratios were observed and allowed to distinguish the diets offered to the animals. Similarly, the results of the present experiment suggest that the renewal of chemical elements (and their isotopes) was sufficient to 'trace' the feeding change from pasture to concentrate even if the isotopic equilibrium in the different tissues was probably not reached due to the short duration of the experiment.…”