Eeeeeshhh. Yet another reason to have a more vegetable-centered diet. Of course, "downer cows" may present a nonsignificant percentage of all cows slaughtered in the US over a month, and plenty of vegetables may be contaminated with E. coli from factory-farm-based or other manure... Of course, this may be the case. But the fact is, with all the common sense and precautions in the world, we all die when we die. "All we have to decide is what to do with the time that is given to us."
I would just rather not contribute to the number of all those poor critters stumbling around with diseases and open sores and being prodded into killing machines. I think the scale is completely out of control. If people ate meat more like once a week or once a month; a couple of times per year, things would be better.
I've mentioned before that I think there's a definite link between respect for human life and respect for animal life. I certainly don't equate the two, please understand. But for both abortion/euthanasia/embryonic research and the slaughter of animals to take place, somebody has to look at a living, breathing creature of God and decide to kill it. When the killing of an animal leaves the intimate hunter-prey model and moves on to a farm, circumstances change slightly. Similarly, when it moves from a small farm to a factory farm scale, the circumstances morph again: now you have a few people in charge of a multitude of animals in very crowded and dirty conditions; those people have to be willing to keep the creatures in those conditions and treat them like any other economic object, and they have to be willing to watch their slaughter again and again. And on the outside, thousands and thousands of people have to be content not to know and not to care how their meat is produced, as long as it gets to the grocery store for a reasonably cheap price.
I hear that keeping all those livestock makes for a powerful lot of gases spewing into the environment. Likewise, it seems that all these people using chemical contraception are pumping an awful load of weird chemicals into the water supply. "Leave no trace." That's the rule of the bush.