A U.S. federal judge on Friday tossed out a lawsuit seeking to block inspections of horses destined for slaughter, potentially clearing the way for the resumption of equine killing for human consumption.

A U.S. District Judge in New Mexico threw out a lawsuit by the Humane Society of the United States and other animal protection groups lodged in July that sought to permanently halt the slaughter of horses.

The suit alleged that the Department of Agriculture failed to carry out environmental reviews before it gave approval to Roswell, New Mexico-based Valley Meat Co., Responsible Transportation, in Iowa, and Rains Natural Meats, in Missouri, to slaughter horses for human consumption.

In a 33-page ruling, Chief United States District Judge Christina Armijo concluded "that the grants of inspection were properly issued." She dismissed the lawsuit, and denied a request for permanent injunction sought by the plaintiffs.

The groups alleged in the suit that horses are given medications not approved for livestock so the waste products of slaughter plants may include pollutants. Following Armijo's ruling, their lawyers lodged a notice to appeal the ruling to the United States Court of Appeals for the Tenth Circuit.

The Humane Society of the United States said in a statement it would "not only appeal the decision, but also work with the states to block the plants from opening in Iowa, Missouri and New Mexico and step up its efforts in Congress to stop the slaughter of American horses."

Horse meat cannot be sold as food in the United States, but it can be exported. The meat is sold for human consumption in China, Russia, Mexico and other countries and is sometimes used as feed for zoo animals.

Congress effectively banned horse slaughter in 2006 by saying the USDA could not spend any money to inspect the plants. Without USDA inspectors, slaughterhouses cannot operate.

The ban had been extended a year at a time as part of USDA funding bills, but the language was omitted in 2011.

Groups have argued for years about whether a ban on slaughter would save horses from an inhumane death or cause owners to abandon animals they no longer want or cannot afford to feed and treat for illness.

Nearly 159,000 horses were exported from the United States to Canada and Mexico during 2012, most likely for slaughter, officials said.

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