A change at the top of the world's largest retailer grabbed the headlines this week. Doug McMillon, the head of Wal-Mart's overseas business, is to be promoted to become the US retail giant's CEO. Elsewhere, there was a raft of M&A stories. Murray Goulburn made what is so far the highest bid for Australian dairy Murrau Goulburn, Associated British Foods lodged an interest in UK rice brand Tilda and Premier Foods is in talks with private equity over investment in its bread arm.