Let us first define the term animal-by-product as given by the Association of American Feed Control Officials.
"...the non-rendered, clean parts, other than meat derived from slaughtered mammals. It includes, but not limited to lung, spleen, kidneys, brain, liver, blood, bone, partially defatted low temperature fatty tissue, and stomachs and intestines freed of their contents. It does not include hair, horns, teeth, and hoofs." [AFFCO]
I can guarantee that a large proportion of people reading that statement thought to themselves "I wouldn't feed my animal those things!" That exact feeling and emotional response those people have is how to describe "The Yuck Factor". We often forget that if you take any of these ingredients and break them down into their protein, carbohydrate, and fat compositions you are left with highly digestible and rich nutrition. Most of these organs have higher nutritional values than muscle (meat)!
Do you think any wild animal has discarded these organs from a carcass because they are icky and gross? It is just another example of how human culture can overshadow our own basic mammalian instinct. Certain dog food manufacturers have taken advantage of the "Yuck Factor" to create niche markets for dog food that advertise that there are no by-products contained.
Consider how many Marylanders enjoy their breakfast with a side of scrapple which is a meat by-product be definition. Those that do enjoy frying up a hot skilled of scrapple are probably easier to convince the benefits of meat by-products than those who are turned off by it. As for the scrapple-shaming audience, I hope I have at least broadened your opinion that animal by-products are completely fine for our pets' consumption. My next post will touch on the other commonly misunderstood ingredient in our pets' food which is corn.
-Dr. Ryan Ashkon Beizavi
Food, W. (2018). The Association of American Feed Control Officials > What is in Pet Food. [online] Aafco.org. Available at https://www.aafco.org/Consumers/What-is-in-Pet-Food [Accessed 4 May 2018]