Expressions of multiple umami taste receptors in oral and gastrointestinal tissues, and umami taste synergism in chickens

Umami taste is one of the five basic taste qualities, along with sweet, bitter, sour, and salty, and is elicited by some l-amino acids and their salts, including monopotassium l-glutamate (MPG). The unique characteristic of umami taste is that it is synergistically enhanced by 5′-ribonucleotides such as inosine 5′-monophosphate (IMP). Unlike the other four basic taste qualities, the presence of umami taste sense in avian species is not fully understood. In this study, we demonstrated the expression of multiple umami taste receptor candidates in oral and gastrointestinal tract tissues in chickens using RT-PCR analysis. We first showed the metabotropic glutamate receptors (mGluRs) expressed in these tissues. Furthermore, we examined the preference for umami taste in chickens, focusing on the synergistic effect of umami taste as determined by the two-feed choice test. We concluded that chickens preferred feed containing both added MPG and added IMP over feeds containing either added MPG or added IMP alone and over the control feed. These results suggest that the umami taste sense and synergism are conserved in chickens.