Palatability of Fish for Dogs.
Despite having significantly fewer taste buds than humans (1706 vs 9000), dogs have a highly attuned sense of taste which means they can detect what they like and dislike from only a small sample. Dogs also have a highly developed sense of smell which works together with the taste buds to accentuate the sense of taste.
Like humans, dogs are omnivores and so have developed preferences for a wide variety of different foods. They can detect bitter, sour, salty and sweet flavours, the latter of which is almost non-existent in cats.
Dogs also possess receptors that are able to detect compounds, such as certain amino acids, that elicit the so-called "Umami” taste. This fifth flavour has been described in humans as a kind of satisfying, savoury taste. In dogs and cats, it is thought that this sense is well developed as it enables them to distinguish between fish and meat, as well as its freshness.
We know that dogs in general will bury bones and return to them later, and eat the most unmentionable things that they find lying in fields and under hedgerows. This leaves the question ‘What makes some of our domestic dogs picky?’
The most likely reason is that many commercial dry foods are bland. They contain highly processed meat meals, produced predominantly from beef by-products, as well as significant levels of cereal. The result is that the stimulating compounds above are simply not present in many of these foods.
An ingredient that appears to contain, and retain, many of these substances is fish. For centuries Asian chefs have added dried fish powder, fish sauce, and fish heads to stocks, soups and sauces to enhance the “Umami” flavour, and also discovered that fermenting these materials enhances this further still. The enhancement seen with fermentation, which is also seen with protein hydrolysis, is primarily caused by the production of glutamate, which is known to stimulate the Umami sensors in the mouth.
Fresh fish also contains significant levels of glutamate itself. Fish oil also contains many fatty acids that are particularly palatable to dogs, and this oil is primarily stored just under the skin. Therefore, cooked fish skin not only provides these oils but also produces attractive ‘Maillard’ flavours. As we know ourselves, on a fillet of fish, the skin and fat beneath are often the most sought after parts.