Response of first-feeding spring chinook salmon to four potential chemical modifiers of feed intake

The feed intake of first‐feeding spring chinook salmon (Oncorhynchus tshawytscha) changed significantly when the amino acid glycine or the ammonium‐containing trimethylamine was added to experimental diets in a 2‐week feeding trial. Glycine enhanced feed consumption, whereas trimethylamine (which occurs in rancid fish meals and oils) decreased it. This effect of trimethylamine may indicate that the fish were sensitive to it as an indicator of the freshness of their feed; this possible sensitivity may play a role in the apparent aversion that salmonids and other fish show toward highly oxidized meals and oils.