No doubt the modern world makes issues complicated and complex.
The Weston Price organization is not the end all and be all on this debate. As I said above, there are traditional cultures that have thrived on vegetarian diets for thousands of years. There are many counter-arguments to the Weston Price arguments. Two of the most extensive nutritional studies performed on California 7th day Adventists and the China Study confer the benefits of being a vegetarian.
I don't know where you got your info on cows only producing milk for one year-- that is incorrect. Cows commonly produce for 10 lactations or more.
From the wikipedia section on environmental vegetarianism:
"According to the USDA growing the crops necessary to feed farmed animals requires nearly half of the United State's water supply and 80% of it's agricultural land. In addition, animals raised for food in the U.S. consume 90% of the soy crop, 80% of the corn crop, and 70% of its grain."
Animal feed is producing far more drain on the resources of this country than the vegetarian diet. There are many agricultural groups that have shown methods such as permaculture to more abundant amounts of food even in small areas of space. Mixing trees in with land crops can be an especially effective way of preserving water and maximizing space (using all 3 dimensions of space.)
If you don't understand the heart aspect of being a vegetarian then I suggest reading some books by Dr. Gabriel Cousens if you have not already. Spiritual nutrition explains this. There is an extremely rich spiritual history of vegetarian groups around the world. Not everyone will understand this. I don't expect you to, but heart's desire to be a vegetarian stems from a similar vein.
No doubt animals die in the production of food. The death of animals is increased by the usage of modern machinery. However, I will say that if you have travelled to rural areas in India and Thailand where people having doing the vegetarian diet for thousands of years there is a much different form of agriculture than Western society uses. In India especially, you will see their solution for the cow question you posed. Meat eaters do not have to carry the burden of culling the cows, at least not in India.
Everyone has blood on their hands. I am well aware that I am taking animal lives even when I eat vegetarian food. If I could have been more involved in the food production, perhaps the death toll would not have been so high. But that is not an option for me in this modern world. The only thing that I can say is that I do the best I can.
Debates about vegetarianism become circular-- no one can ever win. It is like religion and politics. I feel in my heart to follow a certain diet-- this has been strengthened and bolstered by inner experiences I have had. As I become more coherent with what my soul is telling I become stronger.
Everyone has a different life path and a different life mission, so I have never judged omnivores-- I accept them for who they are. Many vegetarians are notorious for pointing fingers and blaming omnivores-- no doubt this has made the situation worse. But omnivores, too, often blame and ridicule. All I can say is that those are not empowering ways of living.
I live my life and I do not even discuss my being a vegetarian with my friends and associates. I only responded to this post, because I wanted to alert the community that I felt it was possible to be a healthy vegetarian and also overcome difficult health challenges. I do know how to be a healthy vegetarian despite being Blood Type O. I can say this is abundantly possible regardless of all the propaganda that exists.
As David Wolfe says, the planet has the worst food ever right now. However, this same situation has also simultaneously allowed the best food ever to be available. Some of the greatest superfoods I have ever seen are coming on to the market right now.
One last observation I would like to make is that more we become connected to our soul within, the less food we need to eat. In India, it is common to see yogis who live on just a few hundred calories a day. Gabriel Cousens talks about this subject more in depth in his books. I saw a talk last year by an Indian man named HRM (his website is online) who has apparently gone for periods of a year or more without food. He claimed that he was observed by a research team from NASA and that the study will be published soon. Whether or not he is telling the truth, I believe that nourishment can be derived from other places than just food. Many people will not understand this subject, and the everyday person will not be able to benefit from it. However, I believe that a day may come when our planet is realligned with many of the more subtle energies that have been known in most traditional cultures. When I say that I am vegetarian for reasons of my heart, it is not something that can easily be explained in words.