To answer your first question. Factory farming affects both humans and the farmed animals, and in addition the farmed animals are horribly treated. Such intensive animal agriculture also leads to diseases that affect humans as well as water, soil, and air pollution, including large quantities of greenhouse gases. It's a vicious circle.
We don't believe we fully understand your question about cattle. 50,000,000,000 land animals are slaughtered for human food every year, so their population is 9 times the human population. If we switch to a plant based diet, there would be a much smaller population of animals, because humans wouldn't breed them. Thus, there would be fewer cattle needing grazing land and supplemented food, which would result in less deforestation, if not an end to it altogether.
Until humans wise up to the damage we are doing to the earth and change, or develop some compassion for the other animals, there is little likelihood that there will be a significant decrease in the number of animals raised for food, that is, unless we have a dramatic climate change, or several rapidly spreading pandemics, and we are forced to change to a plant based diet.
On the other hand, we are putting our hope and faith in compassion, and we're seeing thousands of people beginning to take up the call. If they lead the change to a plant based diet, it will solve 1/5 of the global warming problem.
In the Love of the Lord,
Frank and Mary