Modelling digestion kinetics in pigs : Predicting nutrient absorption based on diet and ingredient properties

Abstract

In pig production, production efficiency is effectuated by formulating diets that meet the pigs’ nutrient requirement for maintenance and production (i.e. growth, reproduction). The amount of nutrients available to the pig, depends on the nutrient content of the diet and on the ability of pigs to digest and absorb these nutrients from their gastrointestinal tract. The availability, but also the utilization of absorbed nutrients for metabolic processes (e.g. heat production, protein and fat synthesis), depends on the kinetics of nutrient digestion after ingestion of feed. Digestion is the aggregated process of passage, hydrolysis, and absorption of nutrients and endogenous secretions by organs and tissues involved. These processes determine at what rate and to what extent (i.e. kinetics) nutrients are digested and absorbed. Current feed evaluation systems, used to formulate pig diets, do not take into account the kinetics of nutrient digestion. To gain insight into the impact of nutrient digestion kinetics on absorption of nutrients in pigs, a computer model was developed as aim of the research described in this thesis. The work described in this thesis provides insight on the quantitative relations between the kinetics of digesta passage and diet viscosity (Chapter 2), diet solubility, and feed intake level (Chapter 3). In addition, the thesis presents further data on the variation in protein hydrolysis kinetics among feed ingredients used in practice for pigs diets (Chapter 4). The dynamic mechanistic computer model: ‘SNAPIG’, described and evaluated in this thesis (Chapter 5), simulates variation in the kinetics of nutrient digestion and absorption in growing pigs. It is a promising tool that can be used to predict the kinetics of nutrient absorption in pigs fed diets varying in feed ingredient and physicochemical properties.