(Photo Courtesy of The HSUS) The Humane Society filed a lawsuit against a McDonald's pork supplier this week, which is used in the popular McRib sandwich.

McDonald's limited-time reintroduction of the McRib has already led to examination of some of the item's questionable ingredients. Now, one of the prime companies from which McDonald's gets its main ingredient for the sandwich - pork - is the target of an SEC complaint.

On Wednesday, The Humane Society of the United States (HSUS) filed the SEC complaint against Smithfield Farms in Virginia, which is one of the biggest suppliers of pork to McDonald's.

The complaint, obtained by the International Business Times, states, among other things, that Smithfield makes false claims in a video series posted on its website this week, entitled Taking the Mystery out of Pork Production. The HSUS alleges that Smithfield engages in cruel treatment of its animals, such as its pigs confinement in gestation crates and the castration of animals without painkillers.

They make outlandish claims: that their pigs live in ideal living conditions, that every need of the animals is met, said Paul Shapiro, a senior director at The HSUS, told IBTimes of Smithfield's video series.

It's hard to imagine that a pig crammed into a cage where she's unable to turn around for months on end would consider that to be ideal.

McDonald's defended itself and Smithfield's practices in an emailed statement to IBTimes, saying it would always require humane treatment of animals by its suppliers.

McDonald's has been a long-time supporter of alternatives to gestation stalls, and we will continue to support the efforts of Smithfield Foods and all of our suppliers to phase them out, Susan Forsell, vice president of quality, said in the statement.

Smithfield Foods was the first major pork producer that committed to phasing out gestation stalls, and we support the company's transparency and progress toward this goal.

Smithfield did not provide comment as of press time.

In 2007, Smithfield, a publicly traded company, announced it would begin to phase out gestation crates. Shapiro said he went to the shareholder's meeting and publicly thanked them on behalf of The HSUS, which is a shareholder in Smithfield.

But two years later, The HSUS wasn't satisfied with Smithfield's lack of a defined timeline. In late 2010, it did an undercover investigation of Smithfield and released its findings in December. It found that female pigs -- more than 1,000 of them -- were crammed in gestation crates, unable to move or turn around for most of their lives. The investigator also did not encounter a veterinarian during his month at Smithfield, and said that three times he had seen pigs thrown into dumpsters alive.

Eight states -- Arizona, California, Colorado, Florida, Maine, Michigan, Ohio and Oregon -- have passed laws to phase out the practice of gestation creates.

It doesn't take a veterinarian to know that locking up a 500-pound animal in a cage barely viable for movement is inhumane, Shapiro said.

Shapiro and The HSUS also took aim at McDonald's, and he said he hoped that despite the popularity of the pork-patty McRib, people would think twice about what goes into its production before buying one.

McDonald's then-community affairs director, Robert Langert, told The Washington Post in 2001 that looking into alternatives for gestation crates was toward the top of our agenda.

With this complaint a decade after Langert's statements, Shapiro said it was fair to call into question whether the company is taking animal welfare seriously.

But McDonald's insists on its commitment to sourcing from suppliers who practice humane treatment of their livestock.

More than a decade ago, McDonald's developed Animal Welfare Guiding Principles in conjunction with leading independent animal welfare experts, including renowned scientist Dr. Temple Grandin, Forsell said in the statement to IBTimes.

We expect our suppliers to follow these principles, adhere to our commitment to continuous improvement and incorporate industry-leading management practices in animal welfare. We hold our suppliers accountable for compliance with our principles.

The schedule for the SEC investigation is as yet unknown, according to Shapiro.

They have a policy of neither confirming nor denying investigations into these types of cases, he said.

Write to Brett LoGiurato at