OLYMPIA, Washington (Reuters) - With Washington state about to embark on a first-of-its-kind legal market for recreational marijuana, the budding ranks of new cannabis growers face a quandary over what to do with the excess stems, roots and leaves from their plants.

Pigs are seen at a farm in Indiana April 20, 2012. REUTERS/John Gress

Susannah Gross, who owns a five-acre farm north of Seattle, is part of a group experimenting with a solution that seems to make the most of marijuana’s appetite-enhancing properties - turning weed waste into pig food.

Four pigs whose feed was supplemented with potent plant leavings during the last four months of their lives ended up 20 to 30 pounds heavier than the half-dozen other pigs from the same litter when they were all sent to slaughter in March.

“They were eating more, as you can imagine,” Gross said.

Giving farm animals the munchies is the latest outcome of a ballot measure passed by Washington voters in November making their state one of the first to legalize the recreational use of pot. The other was Colorado. Both were among about 20 states with medical marijuana laws already on their books.

The federal government still classifies cannabis as an illegal narcotic, and the Obama administration has not yet said what actions, if any, it will take in answer to the newly passed recreational weed statutes.

Matt McAlman, the medical marijuana grower who provided the pot leavings for Gross’ pigs, says he hopes the idea expands with the likely impending expansion of Washington state’s marijuana industry.

“We can have pot chickens, pot pigs, grass-fed beef,” he said.

Draft regulations issued last week to govern the burgeoning recreational-use industry seem to leave open that possibility. The rules dictate that marijuana plant waste must be “rendered unusable prior to leaving a licensed producer or processor’s facility,” adding that mixing it with food waste would be acceptable.

Gross’ pigs were butchered by William von Schneidau, who has a shop at the famous Pike Place Market in downtown Seattle. In March, von Schneidau held a “Pot Pig Gig” at the market, serving up the marijuana-fed pork as part of a five-course meal.

He quickly sold out the remaining weed-fed meat at his shop but plans another pot-pig feast later this summer, he said.

“Some say the meat seems to taste more savory,” he said.

The results beg the question of whether pot-fed pork contains any measurable traces of THC, the mind-altering chemical ingredient in cannabis.

The European Food Safety Authority reported in 2011 that “no studies concerning tolerance or effects of graded levels of THC in food-producing animals have been found in literature.”

The agency also noted that “no data are available concerning the likely transfer of THC ... to animal tissues and eggs following repeated administration.”