Tuesday, December 27, 2016

How much food do pets eat?

I recently had a conversation about an old article on the topic of carbon emissions of pets.  For example, here's an article on the topic from Salon.  Short story, dogs consume enough resources that their carbon footprint is more than your average SUV, while cats have a carbon footprint bordering on an average compact car.

So this led to an interesting thought.  If we didn't have pets, how much more food could we produce?  The thinking was that more food means lower prices and more abundant supply of food for more people and subsequently more people wouldn't go hungry.  Of course, increased supply of food wouldn't be a guarantee that the same supply would be produced.

Other assumptions are that all pet food is human edible (almost certainly false, as some dog food contains bone meal).  But I thought it was an interesting thought experiment to just look at how much food dogs & cats eat and the basically the cost our society may put on food production for non-humans.

Since it's hard to look at all pets, I'll look at just dogs & cats.  I'm going to stick to stats in the United States since it's just easier for this thought experiment.

According to ASCPA there are 70-80 million pet dogs in the US and 74-96 million pet cats.  Lets take the low end of those numbers, 70 million dogs and 74 million cats.

The average number of calories a moderately active adult male needs according to the USDA is about 2600 and for women its about 2000.  We'll take the average of these and say the average adult needs 2300 calories of food a day.

Based on this OSU veterinary chart dogs should get the calorie count according this an advanced formula based on weight.  Unfortunately I cannot find an estimate on the average weight of a dog in the United States.  So I'm just going to go with 25 pounds as the average and hope that's a good guess (I'm likely underestimating given that the most popular dogs are labradors, german shepards, golden retrievers, and bulldogs, which all exceed 25 pounds on average).

1.6 * 70 * (25 pounds / 2.2 (pounds / kg) )^0.75 = 693 calories needed by dog per day

For cats I found this random page saying cats need 20 calories per pound, with Google saying the average cat is 7.9 to 9.9 pounds.  We'll just assume 8 as the average.

20 * 8 = 160 calories needed by cat per day

So under the (likely bad) assumption that all food production for cats & dogs could be converted to human food and assuming all cats and dogs are fed properly, cats & dogs in the US eat enough to feed:

70 million dogs * 693 (calories / dog) / 2300 (calories / person) ~ 21 million people

74 million cats * 160 (calories / cat) / 2300 (calories / person) ~ 5.1 million people

Total ~ 26 million people that could be fed everyday if we didn't have pet dogs & cats

That's a lot of people!  Way more than I thought.  Many of the assumptions above are probably not good ones.  But even general "off by" factors, we could perhaps safely assume it's still enough to feed atleast 10 million people.  Any rounding errors could probably be handled via statistics on other pets not discussed here, the likely larger average weight of dogs, or the low bar I selected on many of the estimates.

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