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

Abstract

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.Keywords: diet characteristic, ketogenic nutrients, meta-analysis, ruminant, splanchnic release ImplicationsPresent work contributes to the evaluation of the energy value of rations for ruminants on nutrient bases. The posthepatic release of ketogenic nutrients was predicted by a meta-analytical approach. Predictors were derived from INRA Feed Tables and the calculated energy balance of animals, which are easy to use in rationing tools.

Net hepatic release of glucose from precursor supply in ruminants: a meta-analysis

“…Because the selected publications did not systematically report the chemical composition and nutritional value of feeds and diets, the feeds and diets from all relevant publications were described according to the INRA Feed Evaluation System (2007) as detailed by Loncke et al (2009c and2015). As the nutritional status of the animals differed among publications and treatments, the availability of endogenous precursors (alanine and glycerol) coming from tissue mobilization (Leng, 1970) was estimated, when relevant, from calculated energy balance (Loncke et al, 2015) and tissue composition of mobilized energy (Supplementary Material Table S1). Because in all these experiments animals were fed with frequent meal distributions to keep nutrient supply and animal metabolism at steady state, it was considered that glycogen stores remained constant and did not contribute to net hepatic glucose output.…”

“…El-Sabagh et al, 2013) but failed to do so in postpartum dairy cows as reviewed by Larsen and Kristensen (2013), even after accounting for methodological effects on liver blood flow measurements. We postulated that a meta-analysis on published data would provide an overview of hepatic conversion of glucogenic precursors into glucose across a wide range of feeding and production conditions in ruminants, as in Loncke et al (2015) for ketogenic nutrients across the liver.…”

“…We first tested whether net hepatic fluxes of precursors responded to changes in total afferent flux (flux of nutrient supplied to the liver via the portal vein and the hepatic artery, see Supplementary Material S1) to the liver or to net portal appearance (NPA). Having demonstrated better relationships with NPA, the study focused on the incremental responses of hepatic fluxes to changes in NPA, thereby describing the responses to increments of 'net' supply of nutrients as in Loncke et al (2015). The impact of analytical methods used to determine liver blood flow was tested.…”

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

“…Meta-analyses were performed according to the heuristic method of Loncke et al (2015) and Sauvant, Schmidely, Daudin, and St-Pierre (2008). All data were examined graphically at each step of the analysis.…”

“…2013). The study effect was considered as fixed to account for the limited number of publications eligible for the meta-analysis (Sauvant et al, 2008) and to acknowledge and explore the influence of experimental conditions on the relationships (Loncke et al, 2015). Having the study effect fixed recognizes the non-random nature of part of the variability present in the data and allows for the exploration of the experimental heterogeneity.…”