Fast-food chain giant McDonald's was quick to respond to complaints lodged by activist investor Carl Icahn over its alleged maltreatment of pigs used in its pork products.

Icahn, who is known for his aggressive campaigns against major companies, launched a proxy fight over the weekend, accusing McDonald's of prioritizing profits of animal rights. To further his agenda, Icahn had reportedly nominated two people into McDonald's board of directors.

At the heart of the issue, Icahn expressed disgust and disappointment in how McDonald's has been complacent in the way suppliers treat their pigs. Icahn and the Humane Society of the United States claimed that McDonald's suppliers are particularly cruel against pregnant pigs.

Icahn and the animal rights group have called on McDonald's to boycott suppliers who still practice placing pregnant pigs inside so-called gestational crates. The pigs reportedly suffer throughout their pregnancies as they are kept trapped inside the confined space.

McDonald's previously promised to help in putting an end to the practice. In 2012, the company committed to phasing out the practice within a decade by boycotting farmers who still place pregnant pigs in gestational crates. Icahn argued that the promised timeframe is already up, and McDonald's has failed to fulfill its commitment.

McDonald's said it already sources around 85% to 90% of its pork from U.S. farmers that do not house their pigs in gestation crates. The Humane Society, which previously applauded McDonald's decision to help phase out the practice, has now criticized the company. The organization said McDonald's is simply moving to reduce its suppliers who are still practicing the cruel process instead of working to put an end to it.

In response to the accusations, McDonald's explained that it would be nearly impossible to completely phase out the practice given the current state of the U.S. pork market. McDonald's argued that the practice is in line with the current veterinary science applicable to large-scale production, which has been in use for decades throughout the industry. The company added that committing to completely shifting away from suppliers that conduct such practices would harm its ability to provide customers with quality products at affordable prices.

McDonald's didn't pull any punches in its response, pointing out that Icahn only owns a small stake in the company and that he is actually a majority owner of another company that manufactures packaging materials for pork and poultry products. McDonald's said it had to be noted that Icahn did not hold such commitments to the other company.