Vegan diets are not bloodless diets," Davis said. "Millions of animals die every year to provide products used in vegan diets."
Few studies document the losses of rabbits, mice, pheasants, snakes and other field animals in planting and harvesting crops. Said one researcher: "Because most of these animals have been seen as expendable, or not seen at all, few scientific studies have been done measuring agriculture's effects on their populations."
Davis presented his research last fall at a meeting of the European Society for Agriculture and Food Ethics, in Florence, Italy. There he questioned the conclusions of animal rights proponents and offered alternatives using the Least Harm Principle. Central to his argument is the unseen mortality that accompanies the production of row crops and grains, staples of a vegan diet, in agricultural systems large enough to sustain the human population.
Davis proposes a ruminant-pasture model of food production, which would replace all poultry, pig and lamb production with beef and dairy products. According to his calculations, such a model would result in the deaths of 300 million fewer animals annually (counting both field animals and cattle) than would a total vegan model. This difference, according to Davis, is mainly the result of fewer field animals killed in pasture and forage production than in the growing and harvest of grain, beans, and corn.
It's obvious that some animals die when their land is taken away for farming, Norris says, "but you take it away only once." It doesn't lead to the continuous slaughter of animals for human consumption, he contends, because once the land is turned into a farm, there aren't that many animals around to kill.
so it isn't just that insects are killed but other animals are killed as well in the process of growing vegetables, etc.
Just goes to show that even if you desire to do no harm, harm is done.