Are tumors common in farm animals flesh?

Answer 1

As in humans, cancer or tumors in animals are somewhat a function of age - young animals have very few tumors while older animals are more likely to have tumors.

If you are asking specifically about the skeletal meat of cows, pigs, sheep, goats, chickens and turkeys (the major slaughter species in the United States), tumors of this tissue are extremely uncommon. The skeletal muscle, where the major retail cuts like steaks or drumsticks come from, doesn't divide often so there are very few cancers that come from these tissues. However, the edible offal (liver, kidney, gizzard, etc.) have cells that divide routinely so the risk of cancer in these tissues is higher, although still quite rare. In the old cow slaughter plants I have worked in, my observed incidence of all cancer (of edible and inedible tissues) was about 1 in 300 to 500 animals; after observing over 1 million carcasses I have yet to see a cancer of the skeletal muscle, although I have observed lymphoma (a blood cancer) form solid tumors in the meat. These carcasses were condemned and not allowed to enter the human food chain.

The good news is, in the United States and most developed countries there is a veterinarian like myself stationed at every slaughter facility specifically to watch for disease like cancer or infections in carcasses. If we see cancer in a carcass, we carefully observe the entire carcass and tissue to see if the cancer has spread. If it hasn't (there are a number of cancers that rarely spread beyond the initial site), we have the cancer and all the lymph nodes associated with it removed and then allow the rest of the carcass (which is now cancer free) to go into human food production. However, if the cancer has spread to any other tissue, the entire carcass is condemned and not allowed to be processed for human food.