In the filing, Jana explained the reasoning behind its move: "Shares are undervalued and represent an attractive investment opportunity. Jana believes that the Issuer has significantly underperformed in shareholder value creation."
The investment firm cited ConAgra's 2013 acquisition of food manufacturer Ralcorp, which "has been followed by disappointing performance for shareholders."
ConAgra released a statement on Thursday, in response to Jana: "ConAgra Foods' Board of directors and management team are committed to acting in the best interests of all shareholders, and we welcome shareholder engagement."
Meanwhile, the analysts at Credit Suisse raised their price target on the stock to $42 from $34 and maintained its neutral rating. "We think ConAgra's board will open a dialogue and listen carefully to Jana's recommendations, assuming they aren't too far-fetched."
The analysts also said one possible recommendation Jana may make is for the company to sell its $4 billion private label division to TreeHouse. "This would relieve ConAgra of the heavy burden and distraction that turning the business around would entail and it would only be modestly dilutive."
Shares soared over 19% since the start of the year and the stock has a market capitalization of almost $17 billion.