Animals Per Calorie
A typical cow produces 7,557 liters of milk Average UK Milk Yield, which equates to about 4.7 million kcal per cow per year Whole Milk. The average cow lives 5 years How long does the average dairy cow live? for about 24 million kcal per cow. However, this cow typically has calves during her three milking years and (assuming as table population), two of them will be culled (in expectation), reducing our estimate to about 7.9 million kcal per life.
The average cow yields 490 pounds of trimmed beef How Much Meat Can You Expect from a Fed Steer?. At about 798 kcal/lb Ground Beef (90% Lean / 10% Fat), that's 391,020 kcal/cow.
A pig yields around 180 pounds of edible meat How Much Meat From a Pig, which amounts to about 187,200 kcal/pig Calories in Pulled Pork Plain (No Sauce)
The average hen lays about 530 eggs The Number of Eggs Given by a Chicken in Its Life Cycle. At 74 kcal/egg 1 Large Egg, that's 39,220 kcal/hen.
Salmon vary widely in size, but yield (very roughly) 14 pounds of meat each How many pounds of fillets can you get from a whole salmon?, equating to about 10,715 kcal/fish [todo: cite]. However, farmed samlon are often feed food made from other fish; this is unaccounted for.
The average chicken yields yields about 0.85 pounds of edible meat and skin Cost and Yield Comparisons of Ready-to-Cook Chicken Products, which is about 589 kcal/chicken Chicken breast, grilled - 3oz.
The average blue crab yields about 2.25 oz of meat Preparing Blue Crab: A Seafood Delicacy, equating to about 53 kcal/crabHow Many Calories in Crab Meat?. In short, we haves
If you think that the problem with eating animals is the fact that they suffer beforehand, then you are probably more interested with the suffering per year Age of animals slaughtered:
If, on the other hand, you think the problem is the fact that we are cutting animals' lives short, then you probably care more about the calories per day-of-life lost:
Of course, difficult questions still remain. Which of these animals deserve moral weight. Alternatively, how much moral weight do each of these animals deserve? Are these animals living in equally bad conditions?
These are not negligible questions. For instance, a naive approach of valuing animals proportional to the mass of their brains would cause a cow to be valued 111 times as much as a chicken per day Reflective Disequilibrium - moving eggs directly below milk in our three tables. You may want to use neuron counts instead, but then the African Elephant beats out humans; if you switch to counting neurons in the cerebral cortex, then the long-finned pilot whale beats us out List of animals by number of neurons - neither of these seem intuitive to me, but that may just be my human-bias speaking.