Lifecyle Biological Efficiency of Mice Selected for Heat Loss

Abstract Text: Feed intake, reproductive performance, growth, and body composition were recorded on mating pairs and sampled offspring from mouse lines selected for high (MH), low (ML) heat loss as an indication of maintenance energy requirements, as well as an unselected  control (MC). Survival rates recorded on mating pairs were used to determine parity distribution at equilibrium. Total input and output of parents and offspring at equilibrium were calculated to determine lifecycle biological efficiency. Offspring output was greatest in MC and lowest in ML mice. Parent output did not differ substantially. Input was greatest in MH and lowest for ML mice for offspring and parents. Lifecycle biological efficiency was similar in MC and ML, while lowest in MH mice. Superior output in MC outweighed lower inputs in ML mice. Avoiding negative response in output must be considered when selecting to reduce maintenance energy requirements.

Keywords: feed efficiency, maintenance energy, selection