Modelling the Control of Energy Partitioning During Sub-Maintenance Feeding in Cattle

In ruminants, the profile of nutrients available for absorption generally differ largely from that present in the ingested feed. The type and amount of feed nutrients absorbed can significantly affect the amount and composition of products. A simulation model was developed to examine the effect that a constant input of energy at four different levels had on the concentration of blood metabolites and the partition of energy in intermediary metabolism. In addition, the effect of changing the proportion of acetic acid and propionic acid on the energy expenditure for maintenance and heat production was examined. The model shows that during nutritional restriction tissues are differentially mobilized and that the greatest losses occur in the liver and small intestine. Also, model analysis indicate that the utilization of absorbed energy is unlikely to be affected by the proportion of absorbed volatile fatty acids (VFA).