[Self] How many days would you have to milk a cow, to get the same calories as you'd get from eating the whole cow?

A cow turns inedible (to a human) materials, into useable calories. You can either milk the cow, and get the calories in the milk, or kill the cow to eat it, to get the calories. As I was eating today, I happened to wonder which is more beneficial: my assumption was that milking is better, or why do it? (not that there aren't other factors to consider in that trade-off, but gotta start somewhere), but how much better is it?

So here's my breakdown for how many days you'd have to milk a cow, to get about the same number of calories as you'd get from eating the edible portion of a whole cow.

How many calories is a whole cow: about 1.1 million edible calories in an average cow

How many calories in milk: Whole milk is 150 calories per 8oz

How Much Milk Does a Cow Produce Per Day: an average of 6 to 7 gallons per day. That's an average across the whole lactation period, but let's take it at face value. I'll split the difference, and call it 6.5 gal/day for that milk giving period.

How long do cows produce milk: about 10-11 months, in every 12-13 months. 10/13 = 0.769, 11/12 = 0.916. Split the difference: 0.8425, averaged across all days.

6.5 gal/day * 0.8425 * 128 oz/gal = 700.96 oz/day 700.96 oz/day * (150 cal/8 oz) = 13,143 cal/day

1,100,000 cal / (13,143 cal/day) = 83.69 days

Milking a cow for 83.69 days, yeilds about as many calories as butchering the cow, and eating it.

How many years can a cow be milked: A dairy cow can only produce milk for about 4 to 6 years. Split the difference, 5 years.

5 years * 365.2425 days/years = 1826.2125 days 1826.2125 days / 83.69 days = 21.82

In terms of usable calories, milking a cow is approximately 21 times more valuable or useful, than raising a cow to kill it and eat the meat.

Of course, this ignores a lot of factors, not least of which is age at time of death, and fraction of lifespan is spent being milked; amount of time, materiasl and effort spent each way, the fact that if you want any cows to do anything with in the future, you're going to be breeding them and thus getting at least some period of time spent lactating as part of that deal; only female cows can be milked at all, bulls aren't usuful for anything but meat (and breeding) no matter how long you keep them; etc. But I think this is enough to satisfy my idle lunch-time musings :)