The history of commercial petfoods is relatively short. While some food products intended for dogs or cats have been available
for over a century, it wasn't until the 1950's when the concept of "complete and balanced" petfoods became established. For
the most part, petfoods have been divided into three conventional forms: dry, canned, and soft-moist (alternatively, "semi-moist").
Traditionally, they have been comprised of animal and vegetable proteins, grains, and added vitamins and minerals.
Within each category of petfood there may be variations. For example, most dry food is extruded, but some is baked. The
extruded product expands with air as it leaves the extruder, whereas the baked is denser. Both are typically around 10% moisture
after processing. Soft-moist foods are often extruded as well, but at a higher moisture content (~33%) and without the introduction
of air. These can take many shapes, from those that resemble ground beef or meat chunks, to the hanging "sausages" often
seen in pet store displays. On a dry matter basis, they are roughly equivalent to dry foods in nutritive value. Their high
moisture content is retained by use of simple sugars (in lieu of the starches incorporated in dry foods) and humectants such
as propylene glycol, or more commonly today, glycerol and organic acids. "Canned" foods (~78% moisture) may be in traditional
cans but also a wide variety of foil-covered plastic trays, pouches, and other containers. However, all must meet the Low
Acid Canned Food regulations to ensure proper processing and safety.
Recent years have seen an influx of new ingredients, new forms, and even new categories of petfoods. All strive to define
their niche in the market place, but must follow the same regulatory requirements as dictated by the Food & Drug Administration
(FDA) and the states that enforce their regulations patterned after the Association of American Feed Control Officials (AAFCO)
model regulations. The veterinarian must be aware of these products and their relative attributes to make sound recommendations
Many, if not the majority of petfood manufacturers, now sell a "natural" line of products. Under AAFCO definitions, a "natural"
product excludes all ingredients that are chemically synthetic. However, it is highly infeasible to formulate a complete
and balanced product without reliance on some synthetic trace nutrients like vitamins, minerals, and taurine. Thus, while
some treat products may indeed be "natural," use of the term in most cases require further qualification. To that end, AAFCO
allows use of a disclaimer, e.g., "natural with added vitamins and minerals" to qualify the addition of synthetic nutrients.
Thus, the bulk of ingredients in a "natural" petfood and a traditional petfood may be the same. One difference is that the
former may not contain chemically synthetic non-nutritive ingredients, such as preservatives, flavors, or colors, except in
amounts that may be unavoidable through good manufacturing practices. Therefore, "natural" preservatives, such as mixed tocopherols
(extracted) or citric acid (fermented) vs. chemically synthetic ethoxyquin or propyl gallate are often used in formulations.
There is little scientific basis to show that "natural" products are safer, healthier or more nutritious. In fact, some have
questioned the ability for natural preservatives to prevent product degradation as effectively as the synthetic, which if
true, could lead to spoilage, loss of nutritive value and potential adverse effects (Cowell et al., 2000). Regardless, to
the extent these few ingredients are important to the pet owner's purchasing decision, these products are very similar to