Calibration of a nutrient flow model of energy utilization by growing pigs

Abstract

A computational framework to represent energy utilization for body protein and lipid accretion by growing pigs is presented. Nutrient and metabolite flows, and the biochemical and biological processes which transform these, are explicitly represented in this nutritional process model. A calibration procedure to adjust the marginal input -output response is described, and applied, using reported experimental results, to determine a complete set of parameters for representing energy utilization by growing pigs. A reasonable value for minimum basal energy requirements is also determined. Although model inputs and outputs need not at any time be converted to equivalent energy flows, to facilitate comparison of model response with that of conventional energy-based models, a simple means to estimate energy flows from model-predicted nutrient flows is described. The well-known hierarchy of marginal (biological) energetic efficiencies with which pigs use different classes of nutrients is predicted by the model, based only on simple biological and biochemical principles. The significance of independent diet and metabolic effects on both energetic efficiency and maintenance requirements is examined using model predictions from simulated experiments. Modelling: Nutrient flows: Calibration: Growing pigsA conceptual framework for representing nutrient utilization by animals was presented in Birkett & de Lange (2001a ). Based on this approach a computational structure with parameters applicable to growing monogastric animals was developed (Birkett & de Lange, 2001b). This model explicitly represents the material flows and transformations of nutrients and derived metabolites in terms of basic and functionally distinct nutritional processes: (1) intake, the acquisition of absorbed nutrients; (2) metabolic, the conversion of absorbed nutrients to energy-yielding and anabolic substrates; (3) faecal excretion of non-digestible materials; (4) urinary excretion of non-metabolizable materials; (5) production, the synthesis, degradation, and retention of body protein and lipid; (6) basal, the residual nutrient requirements not explicitly represented in the other processes. Energy requirements to drive these processes are met by ATP generated from the metabolite pools, providing a single calibration parameter for each of the main processes to adjust its input -output response. This present article describes a logical procedure for calibrating the monogastric model for a particular species, and applies this to derive appropriate parameters for a fully calibrated nutrient flow model of energy utilization by growing pigs. Calibration parametersNutrient response for the primary pathways ( Fig. 1) can be adjusted with six calibration parameters (Table 1). ATPd determines energy requirements for intake, digestion, and absorption of nutrients from faecal digestible DM (fDM). Intake of non-digestible DM (xDM) and its excretion as waste faecal material requires energy expressed in terms of ATPx. Faecal digestible nutrient intake is characterize...

An analysis of the composition of gain and growth of primal cuts of Iberian pigs of 10 to 150 kg body weight as affected by the level of feeding and dietary protein concentration

“…We have recently demonstrated that the growth of body components, the total whole-body chemical composition and the relative growth of tissues in the carcass of the IB pig do not adjust to growth models published for lean and conventional genotypes, implying substantial differences in nutrient requirements (Nieto et al, 2012(Nieto et al, , 2013. Furthermore, when the response of the IB pig at various stages of growth to changes in energy supply at different ideal protein concentrations was analysed, it was also found that energy intake was a critical factor in the pig's response, as previously observed in pigs of lean or conventional breeds, but the utilization of energy for maintenance and productive processes clearly differed: (i) The meta-analysis of data from energy balance trials performed in purebred IB pigs from birth to 150 kg BW (Nieto et al, 2012) allowed us to assume for ME m the value of 413 kJ kg (Birkett & de Lange, 2001); and (ii) it was also found that the partial efficiencies of ME utilization for protein deposition (k p ) and fat deposition (k f ), calculated by means of a multiple regression equation with data from all these balance trials, were 0.397 and 0.641, respectively, and therefore, also less than those of 0.54 and 0.76, which can be calculated from the preferred estimates of energy costs for protein and fat deposition published by NRC (2012). Then, we assumed that k p and k f were fixed values, independent of BW and age, equivalent to ME costs for protein and fat deposition of 60 and 62 kJ g -1 , respectively.…”

Characterization of useful energy content in swine and poultry feed ingredients

“…These models may be refined further to more accurately represent feed and animal effects on energy utilization and to more accurately predict the useful energy supply from feeds and feed ingredients. Birkett and de Lange (2001c). Estimates of regression coefficients are derived from a multiple regression analyses, whereby estimates of diet NE contents generated by the nutrient flow model are related to diet digestible nutrient contents for the 61 diets that were evaluated by Noblet et al (1994a).…”

“…In an experiment that was partially designed to test this modeling approach to representing energy utilization , actual body lipid deposition was predicted accurately in growing pigs exposed to different nutritional regimes (Table 7). The framework can be applied to represent both diet and animal effects on energy utilization in the growing pig (Birkett and de Lange 2001c). The model can also be used to estimate energetic efficiencies and estimate diet DE, ME and NE contents using simulated animal trials.…”

“…These estimates are derived from a multiple linear regression analyses, whereby estimates of diet NE contents generated by the nutrient flow model are related to diet digestible nutrient contents for the 61 diets that were evaluated by Noblet et al (1994a). Estimated daily NE intake is defined as retained body energy (REl plus REp) plus energy from ATPb, and assuming that 1 mol ATP represents 52 kJ NE (Birkett and de Lange 2001c). For comparison, NE supplied by digestible nutrients according to Noblet et al (1994a) and enthalpies of digestible nutrients are presented as well.…”

“…Some concerns raised in the previous section of this paper should be considered, in particular diet effects on animal activity and the impact of dietary fiber of varying botanical origin on animal energetics. (Birkett and de Lange 2001c), mean observed intakes of digestible nutrients and Pd values were adjusted in the model for each treatment. Observed Ld for the basal diet was used to calibrate the basal ATP needs.…”