(FORTUNE Magazine) – HOLY SUPERCOW! Within a couple of years, daily injections may induce a cow to churn out 10% to 40% more milk almost overnight. Monsanto, American Cyanamid, Eli Lilly, and Upjohn are among those working with recombinant DNA to make a commercial version of the bovine growth hormone. Researchers isolate the growth gene in a cow's pituitary gland and transfer it to bacteria cells; after the bacteria multiply, the hormone is extracted and purified. Monsanto, which thinks the worldwide market could be $1 billion a year, appears to be at the head of the herd: Its product has undergone four years of field testing at Cornell University, and the company hopes for Food and Drug Administration approval to market it in 1988. But critics of biotechnology want more study, arguing that increased production would put pressure on cropland (supercows eat as much as 20% more feed) and cause stress in the cows. Some farmers are protesting too. A Cornell study estimates that with supercows the U.S. will need 25% fewer cows and perhaps 32% fewer dairy farmers. Unless price supports are phased out, though, supercows could be a superpain for taxpayers obliged to underwrite still more surplus milk production.