The Maryland Senate rejected five attempts to change an amendment-laden racing bill tonight and gave preliminary approval to a $10.9 million tax break for track owners and horse breeders who face increasingly stiff competition from states with similar legislation.

"We're not giving them a windfall," said Finance Chairman Dennis F. Rasmussen (D-Baltimore County) as he steered the tax relief measure through the Senate during a sometimes-emotional 2 1/2-hour debate.

Rasmussen said the bill would place Maryland's thoroughbred and harness racing tracks "in line with our competition" in New Jersey, New York and Delaware.

The horse-racing legislation could be up for final passage in the Senate as early as Friday. And, if votes tonight on five proposed amendments were any indication, the bill should pass the 47-member Senate overwhelmingly.

Once approved by the Senate, the bill would move to the House, where supporters expect little opposition.

Proponents say the legislation is now virtually untouchable, in part because senators with race tracks in their districts amended it 19 times in Rasmussen's committee last week and also because the bill enjoys the support of Gov. Harry Hughes, Senate and House leaders and the horse-racing industry.

The bill would cut the state's share of the handle, or daily betting pool, from 4.09 percent to 0.5 percent, reduce the track's daily license fee from $1,000 to $25, and also reduce the amount of revenue distributed to local governments from racing.

It would grant an estimated $7.3 million to track owners and $3.4 million in purses to horse owners, who in turn would be expected to use that money to improve track facilities and purses in an effort to keep Maryland horses from being raced in the states with similarly liberal tax arrangements.

The most protracted argument in the Senate tonight revolved around an amendment by Minority Leader John A. Cade (R-Anne Arundel) who, along with a dozen others, sought to make the racing industry more accountable to the state by setting aside the forgiven taxes in a fund that track owners could dip into only for specified improvements to their facilities.

Former Senate president James Clark Jr. (D-Howard) argued against the special account, saying it would be "an impediment to free-wheeling spending" by track owners. In its dealings with the tracks, the state should "cut 'em loose and see what they can do in this competitive field," Clark said. Cade's amendment died on a 31-to-13 vote.

The Senate also rejected, despite impassioned appeals by its five black members, a proposal to require race tracks to establish affirmative action hiring plans.

Sen. Clarence M. Mitchell III (D-Baltimore) said that while blacks make up 40 to 50 percent of the 3.5 million people who attend Maryland tracks each year, they still "want to know why nobody on the other side of the counter taking their tickets looks like them."

Senate President Melvin A. Steinberg argued against such an affirmative action requirement, saying it would be a "bad precedent" to include Mitchell's amendment in what was essentially a revision of state tax law.