Viacom Inc. shaved more than $7 million off potential annual interest costs after its controlling shareholder publicly urged a merger with CBS Corp. just as the media giant was kicking off a $1 billion bond sale.

Keen to get in before a media remarriage, debt investors submitted some $15 billion of orders for the bonds, people with knowledge of the matter said, and Viacom ultimately raised $1.3 billion. The demand allowed Viacom to lower the yield on parts of the offering by about 0.7%.

The Redstone family, which controls both Viacom and CBS, formally asked the companies to consider a merger on Thursday. It came after Viacom, owner of MTV and Comedy Central, last week lowered its profit forecasts, halved its dividend and said it would tap capital markets. Expectations of a deal, which would recombine companies that the family split a decade ago, spurred a rally in Viacom's securities.