The question in the title specifically asks how much jaguars eat not what they eat and therefore I am going to focus specifically on that point. There are many pages on this site about jaguars. Please use the custom search engine on the right hand column to find these pages on a wide range of topics.
My reference point is the best book on wild cat that you can buy which is Wild Cats of the World by Mel Sunquist and Fiona Sunquist.
Captive jaguars in zoos are fed about 1.4 kg of meat per day. Regrettably even this great book says that “there is little information from the wild on how much these cats eat”.
A zoologist Louise H. Emmons estimated that jaguars eat 34 to 43 grams of meat per day per kilogram of bodyweight. This equates to 1.2 to 1.5 kg per day for a 34 kg Peruvian jaguar (this would be a female at lighter end of the scale). This is a similar figure to the one mentioned above for captive jaguars.
Another scientist, Schaller, reported that in the Mato Grosso, Brazil, on three instances a jaguar had eaten less than 5 kg from a capybara kill before abandoning it.
That is about it in terms of my answer to the question in the title. I think it answers the question although I would like a bit more information but as stated it is hard to come by. I hope this helps.
kg = kilogram = 2.20462 lbs (pounds).