I don't have hard facts, but if done correctly, pasturing/grass-feeding animals means it is possible raise and feed a herd without adding energy inputs (aside from the sun and rain necessary to grow the grass). This, at least, applies to animals like cows who are equipped to eat only grasses as a food source. Raising other animals (like pigs or chickens) means you may need to supplement pasture grazing with grains. But there's nothing stopping a farmer from growing those on the farm without much additional energy inputs.
There was a pig (and other animals) farmer who used to have a really good blog. One of the practices he used was to get free discarded milk and by-products from a local dairy to feed his pigs. Instead of the dairy having to pay to discard about-to-spoil whey, for example, he would just accept a few tons of it and feed it to his animals. But that only goes so far, and the supply has to be local or it becomes too expensive to truck in.
You can feed your cows on grass, but the animal density has to be much lower, or the grass will be under so much pressure that it will die out from overgrazing.
Likewise, you can pasture-raise chickens and the eggs/meat are tastier for it, but the number of chickens/sq yd of pasture is much less than you can squeeze into an indoors "battery operation."
If you are concerned with animal welfare -- and I firmly believe that you should be -- these things are difficult problems. On the one hand you want to raise animals in a sustainable manner that allows them a good, if short, life, but on the other, your customers need to be able to afford the food you provide. And it's that final point that is stopping many farmers from doing it.
It is a matter of scale. I'm of the opinion that the FDA and the department of agriculture, in coordination with the factory farms, have made it very difficult for small farmers to survive (Joel Salatin is an excellent source of information on the sort of regulations that are required). The farmer fro whom we buy our meat, eggs, and milk has stated that he runs at his capacity--he does not believe he could take on more animals (even though there is a great demand for his product) without ultimately making life worse for the animals and producing an inferior product.
Can you articulate for me your resolution to what appears to me to be an irresolvable conflict: on the one hand, firmly believing in the welfare of animals and, on the other hand, electing to eat them.
Electively killing an animal is fundamentally incompatible with caring for it as a living thing -- as non-property; something which has the right to live it's life independent of any human's design for it. Without forgoing your intent to eat it, the best welfare you can give an animal is the treatment of property, as a valued investment. Given that you opt for these animals to be killed anyway, your call for their improved treatment is, I expect, designed first to benefit yourself and your own mental and emotional state. It has only the secondary effect of improving the animals' lives.
Um, yeah, whatever. It's your conflict; why do you expect me to resolve it for you?
You can go into complicated justifications or simply believe that the animal should, while alive, be humanely treated. And that it should be killed quickly and as painlessly as possible.
