Partitioning of late gestation energy expenditure in ewes using indirect calorimetry and a linear regression approach

Abstract

Late gestation energy expenditure (EEgest) originates from energy expenditure (EE) of development of conceptus (EEconceptus) and EE of homeorhetic adaptation of metabolism (EEhomeorhetic). Even though EEgest is relatively easy to quantify, its partitioning is problematic. In the present study metabolizable energy (ME) intake ranges for twin-bearing ewes were 220 – 440, 350 – 700, 350 – 900 kJ per metabolic body weight (W0.75) at week seven, five, two pre-partum respectively. Indirect calorimetry and a linear regression approach were used to quantify EEgest and then partition to EEconceptus and EEhomeorhetic. Energy expenditure of basal metabolism of the non-gravid tissues (EEbmng), derived from the intercept of the linear regression equation of retained energy [kJ/W0.75] and ME intake [kJ/W0.75], was 298 [kJ/W0.75]. Values of the intercepts of the regression equations at week seven, five, and two pre-partum were 311, 398, and 451 [kJ/W0.75], respectively. The difference between the intercepts for different weeks was used to calculate EEhomeorhetic. The remaining part of EEgest was considered to be EEconceptus. In conclusion, the good agreement between our values of EEconceptus and those in the literature indicates the method's validity.