Beef farming is more harmful to environment than the production of pork, poultry, eggs or dairy, according to a Bard University study.

Researchers said that cattles produce five times more greenhouse gases, consume six times more water-polluting nitrogen, require 11 times more irrigation water and 28 times more land.

This is the first study to identify and compare the U.S. environmental costs of different meats and animal proteins.

The study "represents a gross oversimplification of the complex systems that make up the beef value chain," Chase Adams, a spokesman for the National Cattlemen's Beef Association, told USA Today.

Adams said that that the beef industry has enhanced its environmental sustainability in recent years. Beefs from the United States are associated with the lowest greenhouse gas emissions as compared to any other countries.

For the study, researchers used U.S. government statistics to determine air and water emissions and the usage of water and land in the lifetime production of beef, pork, poultry, dairy and eggs.

Researchers found that similar environmental footprints were found among pork, poultry, dairy and eggs.

However, lead author Gidon Eshel - an environmental physics professor - said that cows produced all-together different results. Eshel said that cows release methane, a greenhouse gas that is more dangerous than carbon dioxide, in large amounts through the animal's digestive system than pigs, chickens or turkeys.

Researchers said that the manure used to grow feed for cows also releases methane and so does their bodily waste.

The study did not focus on plants or fish raised for human consumption.

The finding is published in the journal Proceedings of the National Academy of Sciences.