A reader, Chris, writes in with this question. I have never really thought about it before, but I put my mind to it a bit today and the answer I came up with is "probably not."
Chris asks because he knows some folks who have come to believe that veganism, or perhaps at least vegetarianism, might be the best way to practice Taoism. Now, I should say right at the outset that I am not a religious Taoist and am not familiar with the practices of religious Taoism. A different answer might be forthcoming from a religious Taoist perspective. But from a philosophical Taoist point of view, I am fairly confident is saying that one need not be a vegan or a vegetarian to follow the philosophical precepts of the Tao Te Ching.
I should also say right up front here that I am one of those people who believes there was no such person as "Lao Tzu." No disrespect for those who hold other views - I have just been too influenced by reading A. C. Graham. So, I guess my answer is really: "the people who wrote the text of the Tao Te Ching were not vegans."
OK, how about some textual support for my conclusion. The most telling point is the first line of passage 60: "Govern a great nation as you would cook a small fish." This suggests that the writers of the text were so familiar with cooking fish that they could invoke it as a metaphor for governing. Had they sworn off eating fish by the time they wrote the text? Who knows. But it seems that they were quite comfortable with the idea of cooking, and presumably eating, fish.
Passage 80 also suggests meat eaters. This stanza describes something like an ideal Taoist society, in the view of the Tao Te Ching. And here people, content in their homes, can hear their "chickens and dogs calling back and forth." The question thus becomes: why do they have chickens? Dogs could have been pets and companions, as well, possibly, as a meal or two. But chickens are probably food. Unless some intrepid historian can come forward to show us that people in pre-Qin China kept chickens as pets, I think we have to assume that chicken-eating was understood as a part of a good, simple lifestyle. The passage also says that people should "find pleasure in their food." A bowl of chicken soup, perhaps?
Killing animals to eat them would be allowed under the idea put forth in passage 29 that things "...sometimes kill and sometimes die." And we could throw in a bit of passage 5 along these lines: Heaven and earth "are inhumane: they use the ten thousand things like straw dogs." Just be careful where you throw the bones after dinner.
I don't see in this a clear prohibition against eating animals. There is, of course, counsel to live, and eat, simply and frugally: "The five tastes blur tongues" (passage 12). But that simplicity can include, it seems to me, a modest carnivorous diet.
If we were to broaden the question out to include Chuang Tzu, I think the non-vegetarian interpretation is strengthened. The great Cook Ting passage (scroll down a bit) shows us that a man can find Way in butchering oxen. Again, even if the enlightened cook is not eating the oxen himself, the eating of oxen is not presented as a bad thing.
Conversely, of course, there is nothing in the Tao Te Ching or Chuang Tzu that would preclude veganism or vegetarianism. If that is an expression of one's Te (integrity), so be it.
In the end, it is more about simplicity and letting go of desire and expectations than it is a matter of any particular diet.