Nearly a year after Raul Kohan, the former head of the drugmaker’s animal health business, was shifted to the No. 2 slot in the wake of the acquistion of Organon’s animal-health unit, he is being placed in charge once again.

At the time, Organon’s Ruurd Stolp was tapped to the combined animal health business, which generated $1.45 billion during the first six months of this year. Now, though, Stolp (see photo) is leaving the drugmaker, although there is no word on his destination.

The move comes amid ongoing turmoil at Schering-Plough, which is still reeling from a dramatic decline in sales of its Vytorin and Zetia cholesterol drugs and a subsequent reorganization designed that involves closing plants and cutting 10 percent of its workforce of 55,000 in order to save up to $1.5 billion (back story).

Interestingly, Stolp was regarded as a dynamic exec, so his departure, which was made by “mutual agreement,” comes as a surprise. As a result, speculation among insiders is that Schering-Plough may consider selling the animal health unit after all, even though ceo Fred Hassan has talked about diversification as a central strategy. Bark our way if you hear anything, okay?