Apomorphine-susceptible and apomorphine-unsusceptible rats as model for High-resisting and Low-resisting pigs: Metabolic differences

This study was undertaken to provide detailed information on the energy metabolism of apomorphine-susceptible (APO-SUS) and apomorphine-unsusceptible (APO-UNSUS) rats, a model for High-resisting (HR) and Low-Resisting (LR) pigs, respectively. It is known that HR and LR pigs differ in the partitioning of ingested energy. To further test the validity of the model, energy partitioning was measured for two weeks using indirect calorimetry. APO-SUS rats had both a higher daily food intake and growth rate (gram/day) than APO-UNSUS rats. When scaled with metabolic body weight, however, both gross energy and metabolisable energy intake did not differ between the two lines. Activity related heat production did not differ between the lines whereas total heat production tended to be lower and non-activity related heat production was lower in APO-SUS than in APO-UNSUS rats. Finally, APO-SUS rats appeared to deal more efficiently with their energy reserves than APO-UNSUS rats. Both rat lines retained similar quantities of protein, but mobilised body fat reserves. APO-SUS rats tended to mobilise less body fat than APO-UNSUS rats. As a consequence, APO-SUS rats still retained energy during the experimental period. In contrast to APO-UNSUS rats mobilised energy reserves. Overall, APO-SUS rats have a more efficient metabolism than APO-UNSUS rats do