Answer:
Nutrition is a very serious health matter. It requires serious study, research, and experience, in health, pathology, biochemistry, processing science, food science/technology, and nutrition. A mere opinion expressed on the Internet does not qualify as a serious assessment that people concerned about health should heed.

Further, consider this from the FDA website:

"Dogs, cats not found in dog food

Because pentobarbital is used to euthanize dogs and cats at animal shelters, finding pentobarbital in rendered feed ingredients could suggest that the pets were rendered and used in pet food.

CVM scientists, as part of their investigation, developed a test to detect dog and cat DNA in the protein of the dog food. All samples from the most recent dog food survey (2000) that tested positive for pentobarbital, as well as a subset of samples that tested negative, were examined for the presence of remains derived from dogs or cats. The results demonstrated a complete absence of material that would have been derived from euthanized dogs or cats. The sensitivity of this method is 0.005% on a weight/weight basis; that is, the method can detect a minimum of 5 pounds of rendered remains in 50 tons of finished feed. Presently, it is assumed that the pentobarbital residues are entering pet foods from euthanized, rendered cattle or even horses."

Please see these links for more information:

Euthanized Pets As A Food Ingredient: http://www.wysong.net/pet-health-and-nutrition/euthanized-pets-as-a-pet-food-ingredient.php

The Pet Food Ingredient Game: http://www.wysong.net/pet-health-and-nutrition/the-pet-food-ingredient-game.php

Myth, Lore and Falsehood in the pet food industry: http://www.wysong.net/pet-health-and-nutrition/fluff-puff-and-smoke.php

The Truth About Pet Food Book (the website you referred to stole the name from Dr. Wysong's book): http://www.wysong.net/products/cat-dog-health-nutrition-truth-about-pet-foods.php

Consider signing up for our free program, The 100 Pet Health Truths. The 100 Pet Health Truths will equip you to become a discerning and educated pet owner. We have condensed Dr. Wysong's 35 years of health wisdom into 100 short and easy messages enhanced with fun graphics and videos. You will also receive coupons totaling $100 for free Wysong products interspersed throughout the program.