This is not a Warren Buffett investment. Portfolio manager Berkshire's Ted Weschler has been buying the shares and signed the agreement with DaVita.
(Read more: Berkshire Hathaway's 15 biggest stock holdings)
In a separate filing, Buffett's business partner Charlie Munger said he has given 100 shares of Berkshire Class A to Harvard-Westlake School, an independent co-ed prep school in Los Angeles with about 1,600 students enrolled in grades 7 through 12.
Munger is a longtime benefactor of the school, which is home to the Munger Science Center.
In an interview with the Berkshire-owned Omaha World-Herald last June, the 90-year-old Munger said he was "deliberately taking my net worth down" by making donations to various schools because "I won't need it where I'm going."
His largest gift to date is the $110 million worth of Berkshire stock he gave to the University of Michigan last April.