IATP Hog Report - Institute for Agriculture and Trade Policy

Section 2
appear to contradict the figures of medical scientists noted above, 44 but
the claim may be misleading. It is difficult to distinguish between the
growth promoting and disease controlling effects of subtherapeutic
antibiotic use. This is because prophylaxis itself promotes growth 45 for the
following reason: 46
When antibiotics stabilize animal health, food animals can
reduce the portion of nutrient requirements associated with
the immune response to fight infection and [instead] use
those nutrients for growth and reproductive purposes.
Growth of Resistance and the Social Impact
Repeated subtherapeutic doses of antibiotics disrupt animals' normal
bacterial flora and promote the growth of antibiotic-resistant bacteria.
Antibiotic-resistant bacteria selected in animals can reach humans and
pass their resistance to bacteria pathogenic to humans or, if pathogenic
themselves, can cause disease that is not easily treatable, prolonging
patients' recovery time. 47 Antibiotics provided in feed or water remain
active and are widely dispersed, contributing to resistance in bacteria they
meet. 48
Stressed animals shed more pathogens in their feces than unstressed
animals. 49 The pathogenic bacteria that survive the gut and are excreted in
the feces are the antibiotic-resistant ones. 50 These bacteria end up in
airborne dust, on the floors, and in the liquid manure storage where they
are preserved until they are spread, along with the manure, on the fields
where they can be detected both in soil and water. 51,52 , 53 , 54 Once on the
fields, antibiotic-resistant bacterial pathogens, as well as parasites in the
feces, can persist and infect wildlife and livestock that ingest them. 55,56
These resistant pathogens may pass through several "vectors" before
multiplying to an infectious dose for the next host. 57
Antibiotic-resistant infections show up regularly in hospitals, a
circumstance that has led to restrictive antibiotic policies in hospitals. 58
Medical practitioners are being urged to limit their prescriptions of
antibiotics. Nevertheless, in the United States, antibiotics continue to be
used as animal growth promoters. And it is possible for farmers, or anyone
else without professional medical or veterinary training, to walk into a
farm supply store and purchase penicillin and other antibiotics, in quantity,
without prescription, and use them without veterinary supervision or any
other restrictions.
There are several possible routes antibiotic-resistant bacteria can take to
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