Olfactory and gustatory sensitivity to some feed-related chemicals in the Atlantic halibut (Hippoglossus hippoglossus)

In farms, Atlantic halibut (Hippoglossus hippoglossus) exhibit low appetite to formulated feeds, resulting in slow growth rate and feed wastage. Addition of attractants and/or stimulants in feeds may motivate them to actively feed in optimum quantities. In this study, olfactory and gustatory (facial) nerve responses to some feed-related chemical compounds were recorded. The olfactory thresholds for 4 tested amino acids were: 10− 7 M for alanine, 10− 6 M for arginine and 10− 4 M for methionine and glutamic acid; at 10− 3 M, relative response magnitudes (expressed as a percentage of response to 10− 3 M alanine) of 20 amino acids varied from 144% for methionine to 19% for aspartic acid. Gustatory nerve responses to 22 compounds including amino acids, bile acids, organic acids, and nucleotides were recorded. Only proline, adenosine monophosphate and inosine monophosphate elicited responses at 10− 3 M; at 10− 2 M, betaine and guanidine monophosphate also elicited large responses. The gustatory threshold for proline response was at 10− 5 M. The results indicate that halibut possesses a generalized olfactory response pattern to amino acids that is comparable with other species and a very specific and narrow taste spectrum.