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Modélisation de la digestion chez le porc en croissance

Abstract : The applications for mechanistic modelling in the field of animal sciences are numerous, and are as important for practical purposes as for research and teaching. One of its most important possibilities is the prediction of the laws of response of the animal to its environment. This approach allows growth, quality of products, excretion, etc. to be taken into account simultaneously even in non-standard conditions. In the pig, most of the models published to date concern the growth of animals. These models include the main determining factors for the partition of nutrients between the functions of maintenance and growth, but the digestive step is generally not described. Besides, the time step considered is most often one day, which does not allow satisfactory modelling of metabolism since the dynamics of nutrient supply can be of importance. Some models describe in part aspects of digestion (gastric emptying, transit, degradations) but no one covers this function as a whole. A simple model of digestion in the pig was developed from data available in literature. lt includes four anatomical compartments (stomach, two portions of small intestine, large intestine) between which the transit of digesta is represented. ln these anatomical compartments, the main digestive events (degradation, absorption, endogenous secretion) are described for the various fractions of digesta (proteins, starch, triglycerides, dietary fibre, minerals). In addition, microbial fermentation is taken into account in the large intestine. The total number of compartments is 44. The time step used is 1 minute. Thus, the model allows the simulation of the evolution of the level and composition of each anatomical compartment with time, as well as the kinetics of absorption of nutrients. The comparison of the outputs of the model with data from literature shows that the general behavior of the model is sound. Its structure can be used as a basis for further developments and could take into account additional variation factors of digestive processes. An application of this model is the study of endogenous nitrogen secretion. Data from the literature on endogenous nitrogen flow at the ileum are quite variable and sometimes contradictory. This parameter is though essential for the interpretation of ileal amino acid digestibility results. A quantitative study performed on about one hundred published results shows that some major variation factors such as feeding level or fibre content of feed can be identified and quantified when the effects of experimental procedures are taken into account. The amino acid profile of endogenous protein flow at the ileum is less variable and an estimation of the non specific part of endogenous secretions is proposed. A complementary approach was to list the various sources of endogenous nitrogen supply in the gut, and to adapt the model of digestion to represent the transit, the degradation and the absorption. The results are in agreement with the trends of the quantitative literature review. Moreover, the simulation allows an estimation of some factors which are difficult to measure in experiments: kinetics of absorption of endogenous amino acids, follow up through time of the quantities of proteins of endogenous origin at the different levels of intestine. Some perspectives for development and improvement of this type of model are then discussed : how to maintain a simple representation of transit that accounts as precisely as possible for the kinetics of digestive events, and particularly of the minimum time of transit through the small intestine; to what extent can a model of digestion be of use in the prediction of feed digestibility, what are the perspectives for the use of such an approach in growth models and metabolism models, and in excretion modelling.
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Contributor : Denis Bastianelli <>
Submitted on : Tuesday, February 4, 2014 - 1:06:25 PM
Last modification on : Thursday, January 21, 2021 - 3:57:51 PM
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  • HAL Id : tel-00941848, version 1

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Denis Bastianelli. Modélisation de la digestion chez le porc en croissance. Science des productions animales. INAPG (AgroParisTech), 1996. Français. ⟨tel-00941848⟩

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