Measurement of nitrogen in small live animals (Weighing about 3 kg) can be used to determine the whole- body protein in the animals. Nitrogen may be measured by IVNAA in which the capture gamma rays of neutron induced are detected and counted. The neutron flux is provided by a collimated 740 GBq (20Ci) Pu- Be source. The 10.83 MeV thermal neutron capture gamma rays from 14N are detected by a 12.7 cm by 10.2 NaI (Tl) detector. The nitrogen of a live rabbit was measured and recorded each day for a period of two months. The statistical error and reproducibility of measurement were around 10%. For a 1000 s irradiation the dose equivalent was 300µ Sv.