Taste in domestic pig, Sus scrofa

Little has bren known about the sense of taste in pigs. Here taste recordings were obtained from the chorda tympani (CT) and glossopharyngeal (NG) nerves of I to 7-week-old pigs. On the whole, the pig's taste acuity was found to be high but quite different from that of humans and several laboratory mammals. Acids elicited the largest response in the whole CT nerve whereas bitter and sweet substances best stimulated the NG nerve. Among compounds sweet to humans, glycine, xylitol, sucrose, fructose and glucose gave the largest responses, while acesulfame-K, cyclamate, D-tryptophan, neohesperedin dihydrochalcone (NHDHC), saccharin and stevioside gave a small response, and alitame, aspartame, super-aspartame, and thaumatin elicited no responses. Monosodium glutamate (MSG) and MSG mixed with guanosine 5'-monophosphate (GMP) and inositine 5'-monophosphate (IMP) elicited large taste responses. Betaine also stimulated somewhat. Tilmicosin(R), and quinine hydrochloride (QHCl), gave large responses, while denatonium benzoate, one of the most bitter compounds known to humans, gave small responses. Hierarchical cluster analysis of 49 single CT and 31 NG fibres separated four clusters of fibres in the CT and in the NG. The H cluster, responding to acids, was the most populous in CT. The second largest in the CT was the S cluster. In the NG the S cluster formed the largest group responding to carbohydrates, glycine and xylitol, responding to some extent to acesulfame-K, stevioside and D-tryptophan, but very little or not at all to alitame, aspartame, cyclamate, NHDHC, saccharin and thaumatin. The Q cluster, sensitive to QHCl, sucrose octaacetate and Tilmicosin, was the second largest cluster in NG. In addition, the CT and NG contained clusters that responded best to MSG alone or MSG with GMP or IMP. In contrast to findings in other species, pigs have few taste fibres which respond to NaCl, LiCl and KCI and in addition these NaCl and LiCl responses, when present, were unaffected by amiloride. This indicates that the pig has a low ability to taste NaCl. The results of this study suggest that recordings from the taste nerves of the pig should be used fcr screening of compounds that are under cons;deration for oral or ingestive use in pigs.