Studies on the digestibility and utilization of the nitrogen of irradiated rumen bacteria by rats

Abstract

SUMMARY Rumen bacteria were isolated from the rumen contents of eight Friesian cattle that had been fed a barley-soyabean diet. These preparations were freeze-dried, irradiated with 1 Mrad and analysed for various nitrogenous components. In nitrogen utilization studies involving both young and adult rats it was observed that the ‘true’ digestibility of the bacterial nitrogen was about 80%, while the net protein utilization (NPU) value was approximately 57. It was concluded that about 20% of the bacterial nitrogen, mainly incorporated in the cell wall, was not absorbed by the rat. On the other hand, about 71% of the absorbed nitrogen was utilized by the growing rat for tissue synthesis. Irradiation with 1 Mrad killed virtually all the rumen bacteria without adversely influencing the nutritional value of the bacterial protein.