Salmon, the supposed “last wild food” (Greenberg, 2010), has become very popular in petfoods. This may simply be marketing; however, there is some nutritional credence to the hype. Salmon has been touted as a “super food” by the human medical community for its content of omega-3 fatty acids. For many of the same reasons, salmon also fits into a solid nutritional platform for a pet’s diet too. So, what do we know about salmon’s use in petfood, and are there any issues?
There are several different forms of salmon available to the petfood industry: salmon meat, rendered salmon meal and hydrolyzed salmon for flavor designations and hypoallergenic diets. At the high-cost end of the spectrum, salmon meat consists of the same sort of fillet found at the grocery, either as whole meat or minced.
Seldom are these offered as varieties of salmon like king, sockeye or coho. More often salmon meat is derived from the “frames” of which the fillet has been removed. These are either ground to include the bone or deboned with a mechanical deboning machine to capture all the soft material (meat and fat) and then frozen into blocks. These “meats” are commonly used in the production of wet foods; some are turned into a slurry for use in extruded foods.
Salmon has been touted as a ‘super food’ by the human medical community for its content of omega-3 fatty acids.Salmon meat, especially the mechanically deboned slurries, consists of a fair amount of moisture (pushing 80%) and modest amounts of protein and fat/oil. The fatty acids within the salmon oils are very rich in omega-3s, making up more than 30% of the total. A significant amount of these omega-3s are the important long chain eicosapentaenoic and docosahexaenoic acids (often called EPA and DHA).
The ash content can be quite variable depending on the type of material and the supplier. The meat is typically not the pretty pink that one finds on the store shelf, but rather a gray-colored flesh similar to what one would associate with other fish. Nutritionally, salmon meat is utilized in a manner similar to that of other meats such as beef, pork, chicken or pollock fish (Faber et al., 2010).
Rendered salmon meal is available on a limited basis. This species-specific fish meal is derived from the remaining carcass components following removal of the fillets for the restaurant and grocery trade. The meal will consist of the meat and bones from the heads and frames, along with some skin and organs. These are rendered (cooked) to remove moisture and the high value salmon oil, then ground to a coarse powder. The resulting meal will commonly exceed 60% protein and 10% fat, with ash of 15-25% depending on supplier.
The digestibility of essential amino acids is similar to other fish meals, and the residual oils contain a significant amount of omega-3 fatty acids (Folador et al., 2006). Due to the content of these polyunsaturated fatty acids, salmon meal needs to be heavily fortified with preservative antioxidants to retard oxidation and remain fresh.
At the heart of the matter is whether there are sufficient wild-caught salmon to support the world’s consumption.Another option often available in the petfood industry is salmon hydrolysates. These are primarily components of “natural flavors” or as a fish option in hypoallergenic diets. The latter requires the meat proteins be hydrolyzed (broken down) to small peptides by protease enzymes to avoid being recognized by the body’s immune system.
Following hydrolysis, the protein is spray dried into a brown/tan powder with a mild fish aroma. The protein content can be quite high (70-90% depending on supplier) with fat and ash levels negligible. When used in pet diets, it can be a reasonable replacement for other quality proteins like poultry by-product meal (Zinn et al., 2009). The amino acid digestibility can be very high (exceeding 90%); but, due to a high proportion of non-essential amino acids, the protein quality can be fairly low (Folador et al., 2006). Further, when compared to other hydrolyzed proteins, the ingredient may lack some binding capability in a food. These factors make it important to consider a complementary protein source when formulating with hydrolyzed salmon.
There is one bit of controversy surrounding salmon that has little to do with petfood and nutrition—specifically, whether the salmon was wild caught or farm raised. At the heart of the matter is whether there are sufficient wild-caught salmon to support the world’s consumption and whether they are inherently a healthier choice for the animal and planet. At present, the Food & Agriculture Organization of the United Nations reports that nearly four times more (2.30 vs. 0.83 MMT) salmon were produced via aquaculture than were caught, and these wild stocks are in decline (FAO, 2008).
A recent Time magazine article by Bryan Walsh captures the essence of the matter: “There just isn’t enough seafood in the seas...to keep up with the global seafood consumption.” However, that doesn’t deter opponents of salmon aquaculture. They point out a number of issues:
The practice of farming salmon might just be the salvation for their wild cousins. - Algae blooms and nitrogen pollution reported in waters around salmon farms;
- The appearance of new diseases and pests such as salmon anemia and sea lice that could threaten the wild species;
- Antibiotic residues found in both fish and surrounding seawater;
- Mixing of weaker genetic traits from escaped farmed salmon that could threaten wild salmon; and
- Farmed salmon contain a higher concentration of dioxins and PCBs in the fatty tissues due to feeding practices.
Unlike animal agriculture that has had some 12,000 years to work out these sorts of issues, salmon aquaculture has been around for a mere 40 years. There is a concerted global effort underway to resolve breeding, feeding and environmental issues, much of it spearheaded by the UN. The decline in wild salmon is primarily a result of disrupted river systems from human land development. With the help of organizations such as the World Wildlife Fund, practices learned from aquaculture are being used to help rehabilitate wild salmon populations where they had previously vanished. The practice of farming salmon might just be the salvation for their wild cousins.
While wild-caught salmon may be the ideal, the benefit from consuming farm-raised salmon outweighs the risks by a wide margin (Foran et al., 2005) and sustains the supply for future generations. The net result for our pets is a nutrient-rich ingredient, regardless of where the salmon were raised.