President Reagan turned up the heat yesterday as the Senate Agriculture Committee prepared to take Congress' first vote on one of his spending-cut proposals, his request that it eliminate a scheduled April 1 increase in dairy price supports.

At the same time, the president drew criticism in the House for swinging his budget ax into medical programs for veterans. The Veterans' Affairs Committee was told that 5,000 doctors and other medical personnel will be dropped in fiscal 1982 and a total of 20,000 by fiscal 1986.

There was also a small break in the logiam that has been holding back presidential appointments to second-level government posts with the announcment of 17 new appointees [Details, page A3].

Reagan's appeal on diary supports, made by White House deputy press secretary Larry Speakes, accompanied an intense White House campaign to win on what is, symbolically as well as in dollar terms, one of the more important proposed spending cuts.

Unless dairy supports are cut back, they will cost the federal government $3.2 billion in fiscal 1986, Reagan warned. In addition, consumers will be paying higher prices, and there will be greater excess milk production, his statement said.

The Senate Agriculture Committee is scheduled to consider the April 1 dairy support increase today. Reagan said that a vote to suspend it is a vital first step in reforming the price support program.

According to the administation's projections its revised support program, which has not been submitted to Congress, would reduce the federal government's cost for diary supports to less than $600 million annually.

Speakers said Reagan wanted to set forth his concerns "in very stark terms." Reagan's message was that, in addition to saving the federal government money, elimination of the April 1 increase would save consumers $270 million in the first year by keeping dairy prices lower.

Reagan said his revamped program would provide "sufficient price protection" for dairy farmers without excessive production or sharply higher consumer costs.

Even with the elimination of the April increase, Speakes told reporters, dairy farm income would rise 14 percent. Total dairy from income is now $18.2 billion, he said.

Reps. Robert W. Edgar (D-Pa.) and Margaret M. Heckler (R-Mass.) and Veterans of Foreign Wars national commander Arthur Fellwock all took sharp exception to the planned cuts in veterans' benefits.

"This particular safety net has a big hole in it," Edgar said, referring to the president's promise not to cut a group of basic benefit programs Reagan calls the "social safety net," and which was said to include basic benefits for veterans.

"I am quite shocked," Heckler said. In addition to the reductions of doctors and others working for the Veterans' Administration Department of Medicine and Surgery, planned VA hospitals in Camden, N.J., and Baltimore have been canceled and construction of others has been stretched out.

The readjustment counseling program for Vietnam veterans, which operates out of 92 storefront centers around the country, will be eliminated, Edgar said.

These centers were a response to the Vietnam veterans' complaints that they have had special problems reentering civilian life after their participation in America's most unpopular war.

Reagan, who also proposes to eliminate a $63 million educational program for Vietnam veterans, has been a constant rhetorical supporter of those who served in Vietnam. He has called that war "a noble cause," and a week ago he described them as having "fought as bravely and as well as any Americans in our history."

Edgar said the total cuts in VA programs for 1982 would be $800 million. Another of the proposed cuts is to eliminate additional staffing for the vocational rehabilitation program.

Reagan was visited at the White House yesterday by former president Gerald R. Ford, who is about to leave on a combination business and private trip to 11 countries.

Reagan gave Ford a letter of greeting to the leaders of those countries where the former president will not be doing business: Ireland, France, West Germany, China and Japan.

Ford's business stops in oil-producing nations will be in his capacity as consultant for Charter Oil Corp., the firm that had entered into an agreement with Billy Carter, brother of former president Jimmy Carter, to negotiate for the purchase of Libyan oil.

After talking with Reagan for over an hour, Ford told reporters that he fully supports the president's economic program and his change of policy toward El Salvador. Ford said he saw no comparison between El Salvador today and Vietnam in the early 1960s.