METABOLIC FATE OF DIETARY NON-PROTEIN NITROGEN IN HETEROPNEUSTES FOSSILIS (BLOCH)

Abstract

The metabolic fate of non-protein nitrogen (NPN) from urea as component
of supplementary diet was investigated in the catfish Heteropneustes fossilis.
Urea substitution (3% by weight of food), replacing approximately one-fifth of
dietary protein (8.6 g protein s 1.38 g N r ) , registered a better growth performance.
An increased intestinal urease activity could be recorded from urea-diet treatment.
The activities of liver arginase, alanine aminotransferase and aspartate aminotransferase
together with the level of blood urea were also studied in response to
NPN-diet treatment. All these indicated possibilities of NPN assimilation. Again,
the bioconversion of dietary NPN to tissue protein was ascertained by mass spectrometric
studies. No gross change in food value was observed when the fish was
fed on the NPN diet over a rather prolonged period