More than 20 million farm animals die on way to abattoir in US every year

Guardian analysis reveals toll of heat stress, cold and trauma amid rise in long-distance and more frequent journeys

Tens of millions of farm animals in the US are dying before they can be slaughtered, according to a Guardian investigation exposing the deadly conditions under which animals are transported around the country.

Approximately 20 million chickens, 330,000 pigs and 166,000 cattle are dead on arrival, or soon after, at abattoirs in the US every year, analysis of publicly available data shows. A further 800,000 pigs are calculated to be unable to walk on arrival.