Britain's FTSE slips from 2016 high as Sky falls

(Adds detail, updates prices)

* FTSE 100 down 0.6 pct

* Sky (LSE: BSY.L - news) leads declines on doubts about Bundesliga

* Commodity shares rise

* Smiths Group (Other OTC: SMGKF - news) rises after acquisition

By Kit Rees and Alistair Smout

LONDON, April 21 (Reuters) - Britain's top share index fell on Thursday after reaching its highest close this year the day before, as Sky shares dropped on doubts over the rights for airing Bundesliga matches in Germany.

Germany's Federal Cartel Office this month approved plans to keep any single buyer from winning all live TV rights to Bundesliga matches. The ruling is expected to raise costs for Sky, which secured all current live rights in 2012, as competition increases.

"We think sell-side analysts expect the cost of Bundesliga rights (for 2017/18 to 2020/21) to increase by between 25 percent and 60 percent," Numis analysts said in a note.

The pay-TV group reported that it attracted 177,000 new customers in its third quarter, helping revenue rise 5 percent for the first nine months, in line with forecasts.

Sky fell 4.9 percent, the biggest decline on the FTSE 100 .

The index was down 37.82 points, or 0.6 percent, at 6,372.44 points by 1048 GMT. On Wednesday, it closed at 6,410.26, its highest since early December.

Shares (Berlin: DI6.BE - news) trading without the right to their latest dividend also weighed on the market. Capita (LSE: CPI.L - news) , Mondi (LSE: MNDI.L - news) and BAE Systems (LSE: BA.L - news) fell as they traded ex-rights. In all, ex-dividend shares trimmed around 6 points off the market.

Commodity stocks were among top gainers, with energy stocks contributing around 6 points to the index. They tracked oil and metals higher, with demand for crude boosted by signs that recent oversupply might be rebalanced .

SABMiller (Xetra: BRW1.DE - news) was roughly flat after reporting it sold 4 percent more beer in its most recent quarter than a year earlier .

Smiths Group rose 4.1 percent, among the top mid-cap risers, after it said it would buy Morpho Detection from French aerospace and defence group Safran (LSE: 0IU8.L - news) for an enterprise value of $710 million.

"While news of an acquisition tends to dent the acquirer's share price (spending cash/diluting shareholders by issuing shares, risk of overpaying, integration risk, etc) the fact that this addition to the SMIN stable can be merged with its existing detection business is being well-received," Mike van Dulken, head of research at Accendo Markets, said in a note.

Small-cap electrical retailer Darty (Other OTC: KESAF - news) shot up 13.5 percent after French retailer Fnac said it would better an offer for the company from Conforama, which is part of South African retail conglomerate Steinhoff.

Darty is at its highest level since June 2011, and has said that it will consider both offers.

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Mike Dolan, Markets Editor EMEA. (Reporting by Alistair Smout; Editing by Larry King and Hugh Lawson (Other OTC: LWSOF - news) )