Jean Vernet

Net energy value of non-starch polysaccharide isolates (sugarbeet fibre and commercial inulin) and their impact on nutrient digestive utilization in healthy human subjects

The energy value of NSP has been expressed as their metabolizable energy (ME) content. The aim of the present study was to determine whether differences in ME and net energy (NE) contents were similar for insoluble and soluble NSP. Nine healthy young men were offered three diets according to a Latin-square design (3 x 3) with three repetitions: diet C (control), diet B (control + 50 g sugarbeet fibre/d) and diet I (control + 50 g commercial inulin/d). After a 16 d adaptation period to NSP isolate, food intake was controlled (duplicate meal method) and faeces and urine were collected for 8 d. A period of 60 h was devoted to measurement of energy expenditure (EE) by whole-body indirect calorimetry. NSP-isolate ingestion induced significant increases in the number of defecations and stool weight resulting from increases in water, DM and microbial mass excretion. After deduction of microbial N, differences in faecal N excretion between diets were not significantly different. Urinary N excretion was slightly decreased by sugarbeet fibre or commercial inulin ingestion but the N balances for the diets were not significantly different. Diet energy, N and lipid apparent digestibilities decreased by only 1-2%. Commercial inulin was entirely fermented and fermentability of sugarbeet fibre averaged 0.886 (SD 0.117). Sugarbeet fibre and commercial inulin ME values averaged 10.7 (SD 1.2) and 13.0 (SD 2.3) kJ/g DM respectively. NSP-isolate ingestion caused significant (sugarbeet) and nonsignificant (inulin) increases in daily EE. The maintenance NE contents of sugarbeet fibre and inulin averaged 5.0 (SD 5.0) and 11.9 (SD 1.3) kJ/g DM respectively. Differences in maintenance NE contents of NSP isolates were much greater than differences in ME values.

Daily energy expenditure and its main components as measured by whole-body indirect calorimetry in athletic and non-athletic adolescents

The objectives of the present study were to determine whether differences in usual physical activity affect BMR, sleeping energy expenditure (EE), and EE during seated activities between athletic and non-athletic adolescents, and to establish individual relationships between heart rate and EE. Adolescents (n 49, four groups of eleven to fifteen boys or girls aged 16-19 years) participated in the study. Body composition was measured by the skinfold-thickness method and maximum O2 consumption (VO2max) by a direct method (respiratory gas exchange) on a cycloergometer. The subjects each spent 36 h in one of two large whole-body calorimeters. They followed a standardized activity programme including two periods of exercise simulating their mean weekly physical activities. Fat-free mass (FFM), VO2max, daily EE and EE during sleep and seated activities were significantly higher in athletic than in non-athletic subjects of both sexes. VO2max, daily EE and EE during exercise adjusted for FFM were higher in athletic than in non-athletic adolescents (P < 0.001), whereas sleeping EE, BMR and EE during seated activities and adjusted for FFM were not significantly different between athletic and non-athletic adolescents. However, sex differences in EE remained significant. Thus, differences in EE between athletic and non-athletic adolescents resulted mainly from differences in FFM and physical exercise. Usual activity did not significantly affect energy utilization of substrates. Finally, individual relationships were computed between heart rate and EE with activity programmes simulating the usual activities of athletic and non-athletic adolescents with the goal of predicting EE of the same subjects in free-living conditions.

Net energy value of two low-digestible carbohydrates, Lycasin HBC and the hydrogenated polysaccharide fraction of Lycasin HBC in healthy human subjects and their impact on nutrient digestive utilization.

The metabolizable energy content of low-digestible carbohydrates does not correspond with their true energy value. The aim of the present study was to determine the tolerance and effects of two polyols on digestion and energy expenditure in healthy men, as well as their digestible, metabolizable and net energy values. Nine healthy men were fed for 32 d periods a maintenance diet supplemented either with dextrose, Lycasin HBC (Roquette Frères, Lestrem, France), or the hydrogenated polysaccharide fraction of Lycasin HBC, at a level of 100 g DM/d in six equal doses per d according to a 3 x 3 Latin square design with three repetitions. After a 20 d progressive adaptation period, food intake was determined for 12d using the duplicate meal method and faeces and urine were collected for 10 d for further analyses. Subjects spent 36 h in one of two open-circuit whole-body calorimeters with measurements during the last 24h. Ingestion of the polyols did not cause severe digestive disorders, except excessive gas emission, and flatulence and gurgling in some subjects. The polyols induced significant increases in wet (+45 and +66% respectively, P<0.01) and dry (+53 and +75 % respectively, P<0.002) stool weight, resulting in a 2% decrease in dietary energy digestibility (P<0.001). They resulted also in significant increases in sleeping (+4.1%, P<0.03) and daily energy expenditure (+2.7 and +2.9% respectively, P<0.02) compared with dextrose ingestion. The apparent energy digestibility of the two polyols was 0.82 and 0.79 respectively, their metabolizable energy value averaged 14.1 kJ/g DM, and their net energy value averaged 10.8 kJ/g DM, that is, 35 % less than those of sucrose and starch.

ATOL: The Multi-species Livestock Trait Ontology

This paper presents the multi-species Animal Trait Ontology for Livestock (ATOL) and the methodology used for its design. ATOL has been designed as a reference source for indexing phenotype databases and scientific papers. It covers five major topics related to animal productions: growth and meat quality, animal nutrition, milk production, reproduction and welfare. It is composed of species-independent concepts subsuming species-specific ones so that cross-species and species-specific reasoning can be performed consistently. In order to ensure a large consensus, three complementary approaches have successively been applied to its design: reuse of existing ontologies, integration of production-specific livestock traits by a large team of domain experts and curators and terminology analysis of scientific papers. It resulted in a detailed taxonomy of 1,654 traits that is available at http://www.atol-ontology.com

Components and variations in daily energy expenditure of athletic and non-athletic adolescents in free-living conditions

The objectives of the study were to determine: (1) daily energy expenditure (EE) of athletic and non-athletic adolescents of both sexes in free-living conditions; (2) day-to-day variations in daily EE during 1 week; (3) energy costs of the main activities; and (4) the effect of usual activity on EE during sleep, seated and miscellaneous activities. Fifty adolescents (four groups of eleven to fifteen boys or girls aged 16-19 years) participated in the study. Body composition was measured by the skinfold-thickness method, and VO2max and external mechanical power (EMP) by a direct method (respiratory gas exchanges) on a cycloergometer. Daily EE and partial EE in free-living conditions were computed from heart-rate (HR) recordings during seven consecutive days using individual prediction equations established from the data obtained during a 24 h period spent in whole-body calorimeters with similar activities. Fat-free mass (FFM), VO2max, EMP, daily EE and EE during sleep were significantly higher in athletic than in non-athletic subjects. After adjustment for FFM, VO2max, EMP, daily EE and EE during exercise were still higher in athletic than in non-athletic adolescents (P < 0.001). However, adjusted sleeping EE was not significantly different between athletic and non-athletic adolescents. Increases in exercise EE were partly compensated for by significant reductions in EE during schoolwork and miscellaneous activities. Thus, the differences in daily EE between athletic and non-athletic subjects resulted mainly from increases in FFM and EE during exercise (duration and energy cost).

Relation of net portal flux of nitrogen compounds with dietary characteristics in ruminants: A meta-analysis approach

Decrease of N intake (NI) with the aim of increasing efficiency of N utilization and decreasing the negative environmental effects of animal production requires assessment of the forms in which N is absorbed. A meta-analysis was conducted on 68 publications (90 experiments and 215 treatments) to study the effect of NI on net portal appearance (NPA) of nitrogenous nutrients [amino acids (AA), ammonia, and urea] in ruminants. In addition, the effect of several dietary energy and protein factors on this relationship was investigated. These factors were: dry matter intake; proportion of concentrate; diet concentrations and intakes of nonfiber carbohydrates and neutral detergent fiber (NDF); diet concentrations of total digestible nutrients (TDN) and crude protein; rumen-degradable protein and rumen-undegradable protein, as percent dry matter or percent crude protein. The effect of species and physiological stage was also investigated. Within-experiment analyses revealed that the NPA of AA-N and ammonia-N increased linearly, whereas the NPA of urea-N decreased (or recycling of urea-N increased) linearly with NI. Besides NI, many significant covariates could be introduced in each NPA model. However, only TDN and neutral detergent fiber intake (NDFi) were common significant covariates of NI in each NPA model. In this database, ruminants converted 60% of incremental NI into NPA of AA-N with no species effect on that slope. However, at similar NI, TDN, and NDFi, sheep absorbed more AA-N than did cattle and dairy cows. On the other hand, species tended to affect the slope of the relationship between NPA of ammonia-N and NI, which varied from 0.19 for the sheep to 0.38 for dairy cows. On average, the equivalent of 11% of incremental NI was recycled as urea-N to the gut through the portal-drained viscera, which excludes salivary contribution, and no species difference was detected. Overall, at similar TDN and NDFi, sheep and cattle increased their NPA of AA-N relative to NI increment by a similar magnitude. The higher absorption of AA-N observed in sheep compared with cattle, at similar NI, TDN, and NDFi, might result from lower losses of AA through portal-drained viscera metabolism.

Empirical prediction of net splanchnic release of ketogenic nutrients, acetate, butyrate and β -hydroxybutyrate in ruminants: a meta-analysis

For energy feeding systems for ruminants to evolve towards a nutrient-based system, dietary energy supply has to be determined in terms of amount and nature of nutrients. The objective of this study was to establish response equations of the net hepatic flux and net splanchnic release of acetate, butyrate and β-hydroxybutyrate to changes in diet and animal profiles. A meta-analysis was applied on published data compiled from the FLuxes of nutrients across Organs and tissues in Ruminant Animals database, which pools the results from international publications on net splanchnic nutrient fluxes measured in multi-catheterized ruminants. Prediction variables were identified from current knowledge on digestion, hepatic and other tissue metabolism. Subsequently, physiological and other, more integrative, predictors were obtained. Models were established for intakes up to 41 g dry matter per kg BW per day and diets containing up to 70 g concentrate per 100 g dry matter. Models predicted the net hepatic fluxes or net splanchnic release of each nutrient from its net portal appearance and the animal profile. Corrections were applied to account for incomplete hepatic recovery of the blood flow marker, para-aminohippuric acid. Changes in net splanchnic release (mmol/kg BW per hour) could then be predicted by combining the previously published net portal appearance models and the present net hepatic fluxes models. The net splanchnic release of acetate and butyrate were thus predicted from the intake of ruminally fermented organic matter (RfOM) and the nature of RfOM (acetate: residual mean square error (RMSE)=0.18; butyrate: RMSE=0.01). The net splanchnic release of β-hydroxybutyrate was predicted from RfOM intake and the energy balance of the animals (RMSE=0.035), or from the net portal appearance of butyrate and the energy balance of the animals (RMSE=0.050). Models obtained were independent of ruminant species, and presented low interfering factors on the residuals, least square means or individual slopes. The model equations highlighted the importance of considering the physiological state of animals when predicting splanchnic metabolism. This work showed that it is possible to use simple predictors to accurately predict the amount and nature of ketogenic nutrients released towards peripheral tissues in both sheep and cattle at different physiological status. These results provide deeper insight into biological processes and will contribute to the development of improved tools for dietary formulation.

Responses of hepatic blood flows to changes in intake in sheep: a meta-analysis.

This work set out to establish the response equations for hepatic blood flows in sheep and the contribution of hepatic arterial flow to hepatic venous blood flow due to changes in intake levels at constant diet composition. The FLORA (FLuxes across Organs and tissues in Ruminant Animals) database was used, and meta-analysis performed. The meta-analysis involved selection of published papers, identification of studies, description and coding of the selected dataset and statistical analysis using a covariance model. Meta-analyses were carried out using a within-study approach. To ensure absence of bias, the analysis incorporated interfering variables and factors studied in between-study comparisons. Variables concerned diet composition; qualitative factors concerned the physiological state of the animals and the methods used to measure blood flow. The results obtained showed that hepatic blood flows were positively related to intake in sheep. The magnitude of the response (as indicated by the slope) varied with the level of intake and the blood vessel (portal, hepatic venous or arterial). Nine linear relationships were established for the portal, hepatic venous and arterial blood flows as a function of dry matter intake (DMI) with below- and above-maintenance levels considered separately. Data obtained at below- and above-maintenance levels were considered together and four quadratic relationships were established for hepatic blood flows as a function of DMI. These relationships expressed a strong effect of intake on hepatic blood flows. The contribution of hepatic arterial to hepatic venous blood flow averaged 18.2%, with a wide variability. It did not vary significantly with level of intake. Although in between-study comparisons the arterial/venous blood flow was positively influenced by the organic matter digestibility of the diet, the relationships we obtained were robust. They can be used in models of net hepatic nutrient fluxes to predict variations and absolute values of hepatic blood flows from variations and absolute values of DMI.

The chemical composition of carcasses can be predicted from proxy traits in finishing male beef cattle: A meta-analysis.

Management practices can contribute to improving carcass quality if carcass quality could be simply evaluated under a wide range of conditions. The objective of this study was to derive quantitative relationships between the most accurate (but laborious) measurements of carcass chemical composition and proxy traits easily obtainable at slaughter (yield grade, subcutaneous fat thickness, marbling, ribeye area and hot carcass weight) by meta-analysis. Data from 34 publications using male beef cattle were used to develop and validate the models. The breeds were characterized according to origin, rate of maturity, production purpose and frame size. The results indicated that the changes in carcass fat and protein can be predicted from the yield grade or subcutaneous fat thickness, and hot carcass weight, with prediction errors ranging between 9 and 12%. Including the breed characteristics in the models did not improve the fit. The relationships are applicable to group values of male beef cattle having light and fatty carcasses from early-maturing British breeds.

Prediction of net hepatic release of glucose using a ‘hybrid’ mechanistic model in ruminants applied to positive energy balance

Ruminants depend on hepatic gluconeogenesis to meet most of their metabolic demand for glucose which relies on availability of precursors from diet supply and animal requirements (Loncke et al., 2010). Several mechanistic models of the metabolic fate of nutrients across the liver exist that have been parameterized for dairy cows. They cannot be directly used to predict hepatic gluconeogenesis in all types of ruminants in different physiological status. A hybrid mechanistic model of nutrient fluxes across the liver is presently being developed (Bahloul et al., 2012), that is calibrated empirically based on meta-analysis (Sauvant and Mertens, 2008) to be applicable to all types of ruminants in different physiological status and to usual nutritional practices. The objectives of the present work were to test the hybrid liver model in its present state of development to simulate the net hepatic release of glucose when the glucogenic/ketogenic/nitrogenous nutrient profile entering the liver varies. This first application of the model was limited to ruminants in positive calculated energy balance, in which the nutrient fate across the liver is mostly directed by mass action laws.