74 R. Weppelman
(1985) reviews several anti-idiotypic antibodies which have shown poten-
tial as vaccines.
 At least in one case, monoclonal antibodies have been shown to be effec-
tive prophylactic agents (Sherman et al., 1983). Certain strains of E. coli
can colonize the intestine of neonatal calves and cause fatal diarrhea. All
of these strains have pili which are hair-like surface structures that bind to
the intestine and anchor the bacteria against peristaltic flow. If calves are
treated with monoclonal antibodies directed against pili immediately be-
fore infection, the severity of the resulting diarrhea is markedly reduced,
presumably because the antibodies prevent anchoring of the bacteria and
thereby reduce colonization.


 TRANSGENIC ANIMALS

 The term "Transgenic Animals" has been defined as those animals that
have stably integrated into their germ line foreign DNA which had been
introduced experimentally (Palmiter and Brinster, 1985). By this defini-
tion, the first transgenic animals were created in 1973 when the virus SV40
was introduced into the germ line of mice by injecting SV40 DNA into the
blastocoel of early embryos (Jaenisch and Mintz, 1974). However, the ex-
periment which brought transgenic animals to the forefront of scientific
imagination and public interest was the experiment by Palmiter et al.
(1982) in which mice were made transgenic with the rat growth hormone
gene. The transgenic mice not only bore the rat growth hormone gene in
their germ line but at least in some cases expressed it at high levels and
grew to a truly impressive size. The extensions of this technology to animal
production are obvious: genes could be introduced into the germ line of
breeding stock which would confer virtually any desirable trait on the
progeny including disease resistance, rapid growth, fecundity, and effi-
cient utilization of feed. Because of the germ line inheritance of the traits,
new traits could be added at the rate of a few per generation until one
obtained an animal totally customized for its intended use.
 At this point, it is instructive to compare the traditional approach to
animal breeding with the transgenic approach. By the traditional ap-
proach, breeders have used the gene pool of the species, including rare
mutations, to create animals bearing the characteristics they desired. By
the transgenic approach, breeders will be able to use the collective gene
pool of all living organisms as well as beneficial mutations which they have
created to achieve the same end. Those who oppose transgenic animal
breeding because it affronts the genetic integrity of the species should note