|
Eric Bush of the U.S. Department of Agriculture's Animal & Plant Health
Inspection Service and LeRoy Biehl of the University of Illinois conducted
their study as part of the National Animal Health Monitoring System's
(NAHMS) Swine 2000 project.
NAHMS is scheduled to publish the results of Swine 2000 this January.
Initial findings and conclusions on the antibiotic/feed additive use portion
of the project were presented by Bush at the U.S. Animal Health Assn.
meeting in Hershey, Pa., last month.
In gathering their information on antibiotics and feed additive use, Bush
and Biehl used a questionnaire to ask pork producers about their use
patterns in weaned market pigs. An evaluation of whether good production
practices regarding appropriate use of antibiotics was a second objective of
their effort. A third goal was to describe the various decision-making
arrangements on swine production sites and determine those with the greatest
influence regarding the use of drugs and medications.
For the NAHMS study, pork producers in the top 17 swine states with at least
100 total inventory on March 1, 2000, were randomly selected to participate
in the study. A total of 2,499 producers completed the first interview,
conducted between June 1 and July 14, 2000. Two subsequent interviews were
conducted on 895 producers between August/October 2000 and December
2000/March 2001. Estimates from the study are weighted and represent 92% of
U.S. hog operations with 100-plus total inventory, the researchers said.
Bush and Biehl reported that for sites with nursery age pigs, 82.7% placed
antibiotics in the feed for growth promotion or disease prevention. The
three most common antibiotics were chlortetracycline (30.1% of sites),
tylosin (23.2%) and carbadox (22.9%). These were placed in the feed for an
average of 24.4, 26.7 and 23.5 days, respectively. On average, pigs were in
the nursery 35-45 days, depending on herd size. Other antibiotics were
placed in nursery feed for 21-28 days except for tiamulin, which was fed for
an average of 16.9 days, the researchers said.
For the study, antibiotic use data for grower/finisher pigs were assessed by
route (injectable, water, feed). For each antibiotic used, producers were
queried about the primary intent of its use (promotion, prevention,
treatment) and, for water and feed antibiotics, the number of days
administered. Figure 1 illustrates the results.
About two-thirds of sites reported administering injectable antibiotics to
grower/finisher pigs, primarily to treat respiratory disease. Only one-third
of sites included antibiotics in water, which was done primarily to treat
respiratory disease. Bush and Biehl said almost all sites included
antibiotics in feed, primarily for growth promotion or disease prevention
and, to a lesser degree, to treat respiratory or enteric conditions.
Almost 90% of the sites that use injectable antibiotics in grower/finisher
pigs did so to treat respiratory disease. The researchers reported that the
most common antibiotic used was procaine-penicillin (30.2% of sites with
grower/finishers). Others commonly used, they said, were oxytetracycline
(16.1%), ceftiofur (14.5%), tylosin (13.8%) and penicillin benzathine
(15.5%), which is not approved for use in swine. Those used less frequently,
they said, were ampicillin, lincomycin and spectinomycin. The researchers
reported that penicillin benzathine is used by a greater number of small
farms and spectinomycin is not used on large farms at all. However, overall
use of injectable antibiotics, as well as use of tylosin, procaine
penicillin and ceftiofur, was found to be more common on larger sites.
One-third of the sites with grower/finisher pigs used antibiotics in water,
said Bush and Biehl. They noted, though, that use varied by herd size from
23% of small sites to more than 75% of large sites. Slightly more than 80%
of the sites that included antibiotics in water did so for respiratory
disease. The three most common antibiotics used were oxytetracycline (8.3%
of sites with grower/finishers), chlortetracycline (6.2%) and sulfamethoxine
(5.1%), the researchers said. While neomycin and tylosin were included in
the water primarily to treat enteric conditions, the researchers said some
small sites indicated that they used neomycin, as well as spectinomycin, to
treat respiratory disease even though they are not absorbed by the gut and
are therefore ineffective in treating respiratory disease. All antibiotics
were placed in the water for an average of five days.
Almost two-thirds of sites with grower/finisher pigs included antibiotics in
the feed for growth promotion, and more than one-third did so for disease
prevention. The two antibiotics that accounted for almost all growth
promotion use were tylosin (31.3% of sites with grower/finisher pigs) and
bacitracin (29.9%). Chlortetracycline was used on about 8% of sites for
growth promotion and on more sites for disease prevention (17.6%) or
treatment (22.5%). Tylosin was also used on a lot of sites for disease
prevention (13.1%) or treatment (11.9%), the researchers said.
Antibiotics included in the feed only for disease prevention or treatment,
the researchers said, were CSP, tiamulin, tylosin and sulfamethazine. The
number of days antibiotics were included in the feed varied for each
antibiotic and also depended on the primary intent for including that
antibiotic in feed, the researchers said. In general, they explained, an
antibiotic was in the feed longer for growth promotion and shorter for
disease treatment.
For their initial look at the antibiotic use data from the Swine 2000 study,
Bush and Biehl concluded that:
* There are many ways to measure and describe the use of antibiotics
(percent swine, percent sites, total grams sold nationally, etc.). Even so,
none of them accurately reflect the concept of "selection pressure";
* Antibiotics are an integral part of swine production;
* Feed is the primary vehicle used for antibiotics intended to promote
growth and prevent disease, while injection is the route of choice of
producers for using antibiotics to treat disease;
* In general, large farms were more likely to use antibiotics, but misuse of
antibiotics was more likely to occur on small farms.
|
