A recent Guardian article has some helpful advice on how to eat meat ethically.
“…much of the information you read about the planet-wrecking capability of cows is based on the most extreme scenario. Yes, grazing cattle on pasture that used to be rainforest releases a lot of carbon dioxide. Yes, cattle kept on feedlots in the US midwest use a lot of water. But there is an easy way to avoid this – buy British.
In Britain, beef cattle tend to be kept outdoors on pasture, simply because we have so much wet grassland that is good for little other than grazing animals. Although feedlots are not unheard of, the average herd size is 28 to 50, as part of a mixed farm. If the cattle are pasture-fed, there is even an argument that they are less damaging to the environment, as permanent pasture absorbs carbon dioxide. Pasture-fed cattle also tend to have more omega-3 fatty acids.”
You can read more on this link