Validation of the doubly-labelled water technique in the domestic dog (Canis familiaris)

Abstract

We validated doubly-labelled water (DLW) by comparison to indirect calorimetry and food intake±mass balance in eight Labrador dogs (24±32 kg) over 4 d. We used several alternative equations for calculating CO 2 production, based on the single-and two-pool models and used two alternative methods for evaluating the elimination constants: two-sample and multiplesampling. In all cases the DLW technique overestimated the direct estimate of CO 2 production. The greatest overestimates occurred with the single-pool model. Using two samples, rather than multiple samples, to derive the elimination constants produced slightly more discrepant results. Discrepancies greatly exceeded the measured analytical precision of the DLW estimates. The higher values with DLW probably occurred because the dogs were extremely active during the 1 h in each 24 spent outside the chamber. Estimates of CO 2 production from food intake±mass balance, which include this activity, produced a much closer comparison to DLW (lowest mean discrepancy 0´3 % using the observed group mean dilution space ratio and an assumption that the mass changes reflected changes in hydration for all except one animal). We recommend an equilibration time of 6 h and use of the two-pool model based on the observed population dilution space for future studies of energy demands in dogs of this body mass.Energy expenditure: Calorimetry: Doubly-labelled water: Dogs

Age‐related changes in the metabolism and body composition of three dog breeds and their relationship to life expectancy

“…Measures of isotope enrichment were based on independent analysis of two subsamples of the water distilled from the blood samples. Because our previous validation study in Labradors (Speakman et al, 2001b) had indicated the two-pool model was superior, we used this model to estimate CO 2 production. The error in individual estimates was determined using the iterative procedures outlined in Speakman (1995).…”

“…The animals were injected via a forelimb vein with an isotonic mix of labelled water containing both 18 O and 2 H, following collection of a blood sample to establish background isotope enrichments. A blood sample was collected from the contralateral forearm at 6 h post-injection, established previously (Speakman et al, 2001b) as the time required for the injected isotopes to reach complete isotopic equilibrium in the body water of dogs of this size. We collected blood at 24-h intervals for a further 4 days.…”

Subclinical iron deficiency is a strong predictor of bacterial vaginosis in early pregnancy

“…As it comes down to the biological plausibility of the observed association, it is conceivable that iron deficiency may affect both innate and cellular immune responsiveness [26,27] at the level of the vaginal mucosa, though we did not identify any previous study on micronutrient status and bacterial vaginosis. The significant association of iron deficiency anaemia with infection has however extensively been demonstrated and most importantly, these effects have been attributed to the adverse effects of iron deficiency on the immune system, even in the setting of mild micronutrient deficiencies [26,27,29].…”

“…The significant association of iron deficiency anaemia with infection has however extensively been demonstrated and most importantly, these effects have been attributed to the adverse effects of iron deficiency on the immune system, even in the setting of mild micronutrient deficiencies [26,27,29]. Interestingly, our observations on the association between iron deficiency and bacterial vaginosis concur with the consistent association between maternal iron deficiency in early pregnancy and a greater risk of preterm delivery [28,29] on one hand, and with the strong and consistent association between bacterial vaginosis in early pregnancy and preterm delivery [11,12,20] on the other hand.…”

“…From this perspective, we hypothesized that micronutrient status during early pregnancy may represent yet another putative biological risk factor for BV, considering that micronutrients, and iron deficiency in particular, affect the host response against bacterial colonization [26], even in the setting of mild micronutrient deficiencies [27]. Moreover, maternal iron deficiency has been consistently associated with adverse pregnancy outcome [28,29] and it has therefore been reiterated that micronutrient status during early pregnancy warrants further scrutiny even among well-nourished women from high-income countries [28].…”