Evidence for a trade-off between growth and behavioural activity in giant "Supermice" genetically engineered with extra growth hormone genes

The "Supermouse," transgenic strain (Tg(MT-1,rGH),Bri2), contains multiple copies of rat growth hormone genes. Supermice exhibit doubled growth rates and body sizes but no increase in mass-specific feeding rates or assimilation efficiencies. Extra growth is achieved entirely by means of increased production efficiency by diverting energy from other processes. Reduction of behavioural activity is one potential mechanism for diverting energy to …