Drug to Boost Milk Output Set for Sale : Biotechnology: While it may not be a blockbuster for Monsanto, it is expected to be a key test of consumer reaction.

Monsanto Corp. on Friday will begin selling a synthetic drug for cows that can lead to significant increases in milk production, thus opening a crucial new chapter in the arduous and controversial development of genetically engineered products.

The drug, to be marketed under the brand name Posilac, is not expected to be a blockbuster for the St. Louis-based company. But the way consumers react to its use could set the tone for the planned introduction of a wide range of foods designed in biotechnology laboratories.

The vocal opponents of Posilac, a genetically engineered form of a naturally occurring substance called bovine somatotropin, or BST, hope to add to a list of creameries and retailers that have already pledged not to carry dairy products derived from the milk of cows treated with the supplement.

Demonstrations, including milk-dumping protests, are scheduled for today in a dozen cities nationwide, including West Hollywood. The critics claim that BST is unsafe.

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Sale of BST was approved by the Food and Drug Administration last year, but was delayed by a moratorium included in last year’s budget bill. The moratorium expires today.

The introduction of BST is not likely to produce any immediate changes in either the availability or price of milk and other dairy products. Scientists in and out of government say consumers will not see any difference between milk from treated or untreated cows and that repeated studies have shown there is none.

However, depending on how widely BST is accepted by dairy farmers, experts have said it could speed up a trend toward fewer but larger dairy farms that has been transforming the dairy landscape over the last 40 years.

Many dairy farmers view BST mainly as an economic issue. In the Midwestern heartland of the dairy industry, which already lags California in per-cow milk production and implementation of technological advances, farmers worry that failure to use the supplement will only increase their disadvantage.

This year, California is expected to cement its status as the No. 1 dairy state, achieved for the first time last September and knocking longtime leader Wisconsin for an ego-deflating loop.

But the opposition campaign, led by longtime biotechnology foe Jeremy Rifkin of the Washington-based Foundation on Economic Trends, has succeeded in putting many farmers and consumers on edge with its claim that milk from BST-treated cows presents a “serious public health risk”--a claim forcefully rejected by the FDA when it approved the use of Posilac.

Monsanto said it will begin accepting orders from farmers today. Delivery of the drug will be immediate, the company said, but it cannot be used until nine weeks into a cow’s lactation cycle (which begins after calving), making its introduction in a dairy herd gradual.

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Rifkin said again Wednesday that BST, by spurring cows to produce more milk, could lead to a greater incidence of infections in the animals, resulting in greater use of antibiotics and thus greater residues of antibiotics in milk. The federal government sets and is supposed to monitor acceptable levels of antibiotic residues.

The demonstration in West Hollywood today is scheduled to take place at a Pavilions supermarket on Santa Monica Boulevard. A spokeswoman for Vons, parent company of Pavilions, said the firm was not aware of the plan.

Vons said it has not taken a position on the use of BST.