A simple modelling approach of regulations in enegy partitioning for the lactating female: application to the dairy goat
Résumé
Predicting kinetics of production, intake and live weight changes in ruminant is controlled by homeorhetic regulations (HR). Aimed at investigating the effect of long term regulations on energy partition, a dynamic model of a lactating dairy goat including simple HR principles was developed. The model predicts the dynamics of raw milk yield (RMY), dry matter intake (DMI), body weight (BW) and reserves anabolism/catabolism through the whole animal productive life. Production potential and weight at maturity are driving inputs. The model incorporates three sub-systems. The reproduction events sub-system coordinates the major events during goat’s life (service, kidding and drying off). The regulating sub-system controls dynamics of body reserves (mobilisation and reconstitution) and milk production through the pregnancy/lactation cycles with a simple four-compartment structure. The operating sub-system represents the major flows of energy through the goat: maintenance, growth, pregnancy, mobilisation, reconstitution, RMY and DMI. External validations indicates that simulated kinetics of milk production and composition are fairly closed to the mean data of the French Milk Control (FMC). However some kinetics extracted after a cluster analysis of FMC cannot be well simulated. Results are discussed in the perspective of integrating this animal model into a herd simulator.