Oak Brook, Illinois - A wealthy investor has launched a bid to gain seats on the board of McDonald's to improve the welfare of animals used by the fast food giant.

Billionaire investor Carl Icahn has launched a proxy fight for two seats on the board aiming to challenge the treatment of pigs by the fast-food chain's suppliers.

Icahn, who holds 200 shares of McDonald's stock, recently slammed McDonald's for failing to end the use of gestation crates for pregnant pigs in its supply chain, saying the practice causes unnecessary suffering.

In a statement confirming Icahn's nominations for two directors, the burger chain said it is on track to achieve its goal of sourcing US pork from confirmed pregnant sows not housed in gestation crates by 2024. The company initially had pledged to end the practice by 2022.

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McDonald's noted that Icahn's stated focus in making the nomination relates to the issue regarding the company's pork policies, which The Humane Society US has already introduced through a shareholder proposal.

McDonald's said Icahn has insisted on new company commitments, and has required all of McDonald's US pork suppliers to move to "crate-free" pork, and set specific timeframes for doing so.

However, the company said the current pork supply in the US would make this type of commitment impossible, and would also harm the company's shared pursuit of providing high quality products at accessible prices.

McDonald's noted that it sources only around 1% of US pork production and does not own any sows, or produce or package pork in the United States.

The company also said that in 2012 it made a commitment to source from producers who do not use gestational crates for pregnant sows.