WHITEHOUSE STATION, N.J. ( TheStreet) -- Merck ( MRK) signed an agreement to sell its 50% interest in the Merial animal health joint venture for $4 billion in cash to its venture partner Sanofi-Aventis ( SNY). Sanofi will own 100% of Merial once the transaction closes. The acquisition is expected to be accretive to Sanofi's adjusted net income from the first year. The companies also signed a call option agreement, in which following the closing of the merger of Merck and Schering-Plough ( SGP), Sanofi could choose to combine the Intervet/Schering-Plough Animal Health business with Merial to form a joint venture that would be owned equally by Sanofi and the new Merck. "These agreements should enable us to proceed expeditiously with the closing of our merger with Schering-Plough in the fourth quarter as planned, and also gain an outstanding animal health business through Intervet/Schering-Plough Animal Health," said Merck Chairman and CEO Richard Clark, in a statement Thursday.