Indeed! One order of Soylent Green, coming right up!
I'm serious though.
Vets are not nutritionists (and you can't be a good nutritionist without first being a biochemist). They are doctors.** They are rarely experts on animal topics outside of canine medicine. In over 40 years as a canine professional, I've seen exactly one vet who knew the first thing about nutrition beyond what's printed on the bag. Science Diet is all about marketing, and they are very,
very good at that. They have 40 years of "it's so good that we only allowed it to be sold through vets" behind 'em. This is just as convincing to the average veterinarian as it is to average consumers.
** Well, the older ones are. More recent graduates are being taught marketing more than medicine. I've seen some that I wondered if they learned surgery from their local butcher.
[I was a biochem/microbiology double major, back-when. I still have a few clues about this stuff.]
The wonder isn't that salmonella is occasionally found in chicken products (pet or human). Rather, that it's not an everyday problem. Know why you're advised to keep raw chicken away from other food, wash your hands after touching raw chicken, etc??
Salmonella is not a contaminant.
It is a natural inhabitant of poultry. If you have chickens, you have salmonella. So the problem isn't keeping it out of the food chain, but rather preventing the existing salmonella from becoming a health issue. So we wash and cook our chicken for human consumption. And scrap meat/byproducts such as goes into pet food are heat-processed (ie. cooked) to kill bacteria, but like all bulk processes, it isn't perfect.
Incidentally, salmonella is found naturally in chickens' ovaries. Layer chicks are dosed with tetracycline to kill it off, and this is why we no longer have a problem with salmonella in eggs (at least, if produced in a modern facility that eliminates contact with natural sources of salmonella), despite that we use billions of eggs, and not always cooked.
Oooookay. Let's see if I can clear up some misunderstandings about how commodities and bulk manufacturing works.
There are NO vertical manufacturers (that is, who control every stage of production from raw materials to finished product) in the dog food industry. The only one with even a nod to that is Purina, because they do run a big farm and research facility. (And its production wouldn't cover a day's worth of dog food, nor all the ingredients.) Everyone buys major ingredients from the commodities market.
And here's how that works (somewhat crudely, as this isn't my field):
--Farmer grows raw material (grain, chickens, whatever).
--Broker buys raw material, which is then pooled with raw materials bought from tens of thousands of farmers. (And the edible waste from human food processing, such as peelings from the potatoes that go into chips. Chicken in dog food got to be a big thing as a byproduct of Chicken McNuggets.)
--Broker sells bulk lots raw material to a processing facility, such as a flour mill or rendering plant. What they get comes from a common pool of such material, not necessarily from the same lots the broker bought from the farmers. (A lot of it gets moved around on paper.)
--Processing facility does its thing and sells the bulk ingredient (now turned into flour or meat meal or whatever) to a commodities broker.
--Commodities broker pools that with product from perhaps dozens of other facilities. It may even be pooled with imported product. (That is, when you order 50 tons of X, the broker orders 50 tons from whatever sources he has on the hook. It isn't stored all in one place. Some may be in a silo in North Dakota and some on a barge in Long Beach Harbor.)
--Pet food manufacturer contracts for N-many tons of various ingredients (which come from various brokers and various pooled sources). They have NO control over where the ingredients came from or how they were processed up the line, tho they can specify grade, or sometimes country of origin.
This is true for human food too, for pretty much anything on your grocery shelves that isn't flat out labeled "locally produced".
The ingredient is inspected multiple times all along the line -- as raw material, processed material, on arrival at the dog food plant, during production, and as a finished product. [In wet years, cereal grains undergo extra inspections because wet weather at harvest increases the risk of aflatoxins from naturally-occuring fungus.] But you can't inspect every bit of the several million pounds in any single batch. So samples are taken -- one bag out of some tens of thousands of bags is good practice.
And if anywhere along the line a contaminant is found, the entire batch is discarded (or recalled), because the
assumption has to be made that it is a batch issue and not a spot issue. Fact is most probably ARE spot issues, but they don't take the chance. The flipside is that spot issues will be missed, because you can't open and inspect every bag nor every nugget from every bag, and that is what you'd have to do to catch every spot issue. (This is why once in a blue moon you'll find a whole chicken foot in a bag of dog food.)
Far more is discarded (well, more likely recycled into fish food) and recalled before it ever hits the retail shelves than the consumer ever hears about -- in fact over 90% of recalls happen before the product reaches the retail market.
This is the reality of bulk production. It is not perfect at any level, because the sheer volume required means it cannot be perfectly controlled or perfectly tested.
And the total volume is so huge that
a tiny fraction of a percent deemed 'bad' translates into 50,000 bags recalled. This is not "lousy quality control". This is the average consumer having no idea what a miniscule fraction of the product that really is, or how the entire process works, or how well best-practices keep naturally-occurring contaminants down to a minimum.
To add to the confusion, very few dog food brands actually own their feed mill; doing so is simply too expensive (millions of dollars in startup costs). Most contract the production process to Diamond or Mars, or less often to Purina or various smaller manufacturers; or more rarely and for very small volumes, to a privately-owned feed mill (which is what I did. Minimum batch nowadays is typically five tons.)
The majority of premium-brand pet food on the market is actually made by Diamond. Used to be you could reliably ID any Diamond-made product by "made in Meta, Missouri" on the label, but they've since acquired some other facilties.