SCIENCE CLOSES IN ON THE SUPERANIMAL Genetic researchers have mastered giant mice. Now they are trying to raise fast-growing livestock for commercial breeding.
By - Edward C. Baig

(FORTUNE Magazine) – PIGS THE SIZE of cows? Cows the size of elephants? Maybe. By injecting modified human growth-hormone genes into the just-fertilized eggs of mice, scientists have created new generations of oversize rodents. As University of Washington molecular biologist Richard Palmiter says, ''There's not much of a market for big mice.'' But the same genetic tinkering, called recombinant gene transfer, is beginning to show results in sheep, pigs, and other farm animals. So far the results have been marginal. In typical experiments with livestock, fewer than 6% of the genetically altered eggs have produced offspring that embody the desired characteristics. But the animals can reproduce, and their young carry the same traits. Scientists hope for a higher ratio of successful eggs in one of the biggest experiments yet, run by a consortium of three Ohio universities. Early in March, at Ohio University's Edison Animal Biotechnology Center, the first of more than 2,000 sows that are being injected with growth genes will produce a litter. Thomas Wagner, a molecular biologist who directs the state-financed center, is hoping that 20% of the eggs will produce superanimals. Those piglets, he suspects, could grow to twice the size of normal pigs. More important, they should reach market size in three months instead of the roughly six required for normal porkers, and probably will consume much less feed. Supercritters are possible because scientists have been able to isolate and manipulate genes with specific traits. Researchers can incorporate these genes into the two strands that make up the double-helix DNA molecule, positioning the new genes in the strands so that they direct the body to produce certain proteins and hormones at precise times. By constructing their own versions of DNA, the researchers can improve such functions as growth rate, resistance to disease, and milk production. But getting the new DNA into an egg is difficult. In the Ohio pig project, for example, young females are given hormones that induce some 50 eggs during ovulation, roughly triple the normal number. The eggs are artificially inseminated, then surgically flushed out of the sow's body and placed in petri dishes. For two to three hours after fertilization, chromosomes from the male and female remain separate in what are called pronuclei. That's when the scientists perform their delicate operation, microsurgically injecting the new genes into the male pronuclei in hopes that they will join the DNA strands when the pronuclei combine to form an embryo. Scientists implant the surviving eggs in an adult female. Then they wait during gestation, which in the case of pigs is precisely three months, three weeks, and three days, to see which offspring have the desired traits. So far the process has been hit-or-miss, with lots of misses. Wagner thinks that progress will come as scientists better understand such things as how many genes to use and when to inject them. Even raising the success rate a few percentage points would allow researchers to speed up the development of animals suitable for commercial use. Superhogs are likely be the first test- tube farm animals, since pigs develop more eggs and have a shorter gestation period than cattle. But scientists see no reason why the technology will not eventually work with any animal, including man. The commercial possibilities only begin with faster growth. Pigs could be engineered to produce leaner pork chops, cows to provide specific grades of milk for different uses: high in protein for making cheese, low in fat for skim milk. Animals could also be designed to produce new medical vaccines. Though a dozen universities around the world are working on recombinant gene transfer, corporations have so far shown little enthusiasm for playing God with animals. Two privately held companies, Granada Genetics Inc. of Marquez, Texas, and Biosyne Corp. of Houston, are working with animals ranging from goats to cattle; a few majors, such as W.R. Grace and Monsanto, | are helping to underwrite university efforts. Privately held Embryogen Inc. of Athens, Ohio, is helping to finance Wagner's project and hopes to market the successful progeny to large pork producers. Most big companies, however, are putting the bulk of their genetic research dollars into plant or other biotechnical projects. They think animal technology is still too uncertain, and believe they can achieve most of the benefits with conventional breeding techniques. Says Wagner, ''I doubt there's more than $5 million of private investment in animal gene-transfer research nationwide.'' That could change rapidly if he or other scientists achieve a solid success.