P2.94 Thursday, Jan. 5 Selection on maximal metabolic rate in mice alters body mass but not body composition DOWNS, C.J.*; WONE, B.; DONOVAN, E.R.; HAYES, J.P.; Univ.of Nevada, Reno; Ben-Gurion Univ. of the Negev, Israel; Univ. of Nevada, Reno; Univ. of Nevada, Reno; Univ. of Nevada, Reno email@example.com
Many life history traits, including growth rate, are often correlated with metabolic rate. Hence, selection of metabolic rate might cause correlated response in growth trajectories and final body mass and final body composition. We tested how selection on maximal aerobic metabolic rate (MMR) and basal metabolic rate (BMR) in laboratory mice (Mus musculus) affected growth trajectories, final body, mass, and body composition selected for mass-independent metabolic rates. As part of a larger experiment, three selection treatments were used: selection for high mass-independent MMR (high-MMR), selection for high mass-independent MMR and low mass-independent BMR (ANTAG), and no selection (i.e., randomly bred controls, CONT); each treatment had 4 replicate lines. After 7 generations of selection, MMR was greatest in high High-MMR mice and lowest in CONT mice; BMR was greatest in high-MMR mice and lowest in ANTAG mice. High-MMR mice were significantly heavier than CONT and ANTAG mice at weaning (21-days old) and at final body mass (19- to 21- weeks old). There were no overall differences in mass-independent body composition (i.e., fat mass, ash-free lean mass, ash mass, and water mass). This suggests a proportional increase of each component of body composition with the absolute increase in mass. At the level of selection treatment, our results agree with previous work that body mass was positively associated with BMR and MMR. However, at the level of selection treatment, there were no relationships between body composition and either BMR or MMR.