Some veterinarians say that feeding animal bi-products, which are commonly found in most mass produced pet foods, to animals increases their risks of developing cancer and other disease. Specifically in regards to dog and cat food, animal bi-products are almost always a chief ingredient, ranging from ligaments, lungs and intestines, to unhealthy blood and bone meal. So what's so bad about animal bi-products you ask? The answer to this question lies in the animal agriculture industry itself. Considering that approximately 50% of each animal carcass that is slaughtered for human consumption is actually considered "unfit for human consumption", if it were not for the pet food industry to make use of these carcasses, the animal agriculture industry would be making a lot less money than it is. The bottom line is that most pet food is simply made up of nutritionally lacking meat bi-products that may contain cancerous organs - all of which is certainly unfit for human consumption. And while it's true that these meat bi-products contain protein and other nutrients, the quantities are sorely missing. The choice cuts of lean muscle tissue, which our cats and dogs need for their natural well being, get packaged for human consumption instead. Furthermore, the way in which most pet food is cooked and packaged removes even more of the nutritional value that is hardly there to begin with. There are actually no assurances of nutritional adequacy because ingredients are not analyzed, nor are the bioavailability values of nutrients asserted. The cooking and packaging process often makes pet food even more potentially harmful to our pets health. Most pet food is rendered, which is essentially the process of removing water and bacteria. However, rendering also compromises nutritional value because it can destroy natural proteins and enzymes found in raw pet food. Additionally, rendering does not necessarily kill the unhealthy hormones and antibiotics that are often fed to animal livestock.