While Europe has been embroiled in a horse meat scandal since January, five new US slaughterhouses have filed requests for licensing at the Agriculture Department (USDA), a spokesman told AFP.
One of them, in the New Mexican city of Roswell in the US Southwest, could start processing a hundred horses a day starting as early as this month.
"Everything is completed and ready to go," said lawyer Blair Dunn, who represents owner Ricardo De Los Santos. According to Dunn, the USDA has confirmed the plant has passed inspection and that final authorization should come through within a matter of days.
The meat will be exported, mainly to Japan and to Europe, where controversy has erupted over products labeled as beef containing horse meat, but where horse meat nevertheless has a market.
But the future of the plant and others like it is far from assured, with animal protection groups and their allies in Congress trying to pass laws banning horse meat production.
Lawsuits and votes in Congress led to the closure of the last three horse slaughterhouses between 2007 and 2011. However, lawmakers later failed to renew the ban, a lapse some now want to correct.
"Horses are not bred for human consumption -- they're companion animals, similar to dogs or cats," said Patrick Meehan, a Republican from Pennsylvania who has proposed a complete ban on the industry in the House of Representatives.
"Not only is it inhumane, it's unsafe: over the course of their lives, horses are regularly treated with drugs that are potentially toxic to humans if ingested," he told AFP over email.
In addition to prohibiting slaughterhouses on US soil, lawmakers also want to ban the shipping of horses for slaughter abroad, where they say the animals face a "cruel" death.
Nancy Perry, of the American Society for the Prevention of Cruelty to Animals, or the ASPCA, agreed that slaughtering horses "simply can't be done humanely."
"The process of slaughter is supposed to be done in such a manner that the animal is not supposed to feel any pain," she explained.
But horses "will immediately throw their head when the stun gun is supposed to be applied to a precise place in the brain," so they will have to "be hit two, three, four, multiple times," Perry added.
After the 2007 closures, horses began to be sent to slaughterhouses in Mexico and Canada -- to the tune of around 100,000 a year, peaking in 2012 at 167,000 horses.
This year, sales to Mexico have already grown 18 percent over the same period in 2012.
The animals -- unwanted because they are too old, tired, sick or simply because they failed to meet their owner's expectations -- sell for an average of $2,140, according to government figures from 2004 and 2010.
The horse industry, supported by veterinarian association AVMA, says that a slaughterhouse is better than the alternatives.
With euthanization costing about $500 per horse, many owners are more likely to abandon the unwanted animals into the wild, where, especially in the drought-stricken Great Plains of the central United States, they risk dying of hunger.
"Some people abandon them; I've heard stories of people in the middle of the night bringing them to other people's farms, bringing them on neighbors' properties," said Ericka Caslin, director of the Unwanted Horses Coalition, which is fighting against a ban on horse slaughterhouses.
But Perry stressed that there were other options available beyond slaughterhouses, abandonment or euthanization.
There are more than 700 sanctuaries where horses can finish their days in peace, without fear of ending up on a plate.