Preventive methods replace antibiotic
growth promoters: ten years experience from Sweden
Swedish Animal Health Service, Johanneshov, Sweden
The farm industry in Sweden, a member of the European Union since 1995, works under the same economic conditions
as other EU-member states. In 1986 antibiotic growth promoters (AGP) were banned in Sweden, and the only allowed
use for such drugs, as for other antibiotics, was by prescription only, in therapeutic doses, to cure or prevent
disease. Our ten years' experience without using AGP has demonstrated that under good production conditions it
is possible to reach good and competitive production results for rearing of poultry, calves and pigs. Due to the
new legislation in combination with efforts to focus on correct use of antibiotics in animal production, the total
use of antibacterial drugs administered to animals decreased by approximately 50% during the ensuing ten-year period.
The dramatic change in AGP use has not negatively influenced the animal health status or productivity, with the
exception of piglet production (1).
In anticipation of the ban, intensive efforts were made to control necrotic enteritis caused by toxins from Clostridium perfringens,
a disease considered a potential threat in the absence of AGP. Many factors such as hygiene, management, feed,
and the construction and climate of stables could contribute to the outbreak of this disease (2, 3). Experiments
were carried out (4) and their results continuously implemented through close collaboration between the feed industry
and the producers. The most important changes in poultry feed were reduction in protein content, increase in fibre,
and supplementation with enzymes. Today, cases of necrotic enteritis can often be traced to exceeding the recommended
level of protein in the feed.
Emphasis was placed on improving animal environment because many diseases including necrotic enteritis have multifactorial
risk profiles. For example, air flow was found to be inadequate in several units. Improvement in animal environments
and other changes were facilitated by the low number of producers. There were approximately 200 in 1986, and 170
in 1997, a period in which their annual production increased from 39 to 65 million chickens. The producers collaborated
in creating a national standard as a target for all production units, and a special bonus was given for good animal
management and care. These tactics also improved the overall quality of production.
The AGP ban was implemented quickly without sufficient time for producers to adjust to the new situation. This
created initial difficulties reflected in the approximately 90% of broiler chickens under continuous treatment
with virginamycin during the first year of the ban; in 1987, the treatment frequency was 100% in order to prevent
outbreaks of necrotic enteritis.
During 1987 however, prophylactic virginamycin was replaced with a two-day treatment with phenoxy methyl penicillin
in drinking water when necrotic enteritis outbreaks occurred. By the beginning of 1988, the new treatment had largely
replaced the use of virginamycin. Today, prophylactic treatment is needed only infrequently and when required,
tylosin is the treatment of choice. Thus antibiotic use for treatment of necrotic enteritis has decreased from
about two tons of virginamycin in 1987 to 100 kg of phenoxy methyl penicillin in 1988 (8) and to a negligible level
It should be noted that coccidiostats of the ionophore type now used also have antibacterial effects and act prophylactically
against necrotic enteritis. In spite of this, however, the sanitary situation of broiler chicken rearing in Sweden
today would not have been achieved without the aforementioned enforcement.
Goals for the future include the replacement of coccidiostats with a vaccine. A vaccine is currently available
but is relatively expensive. Vaccines against coccidiosis are used in pullets and more rarely in laying hens. In
the future, these vaccines will be important for broiler production. At that point, reducing the use of coccidiostats
will require alternative preventive measures against necrotic enteritis, preferably by the use of a vaccine.
Before 1986 most piglets received AGPs, olaquindox or mecadox (50 ppm), from birth until their delivery to the
finishing units at age 10-12 weeks. Thereafter, pigs were given AGP (avoparcin or virginamycin) until slaughter
at approximately 7 months of age.
The ban on AGP did not create obvious clinical problems for growing/finishing pigs which, in 1984, consumed 7.8
tons of active ingredient of virginamycin. In fact, the mean daily weight gain approximately 850 grams in 1997
is not known to be larger in countries where AGP is used.
During the first year of the ban, the proportion of antibiotic-treated weaning piglets was drastically reduced
from 100 % to 12 % (Fig 1), but significant clinical problems emerged in these piglets. The post-weaning mortality
in the first year after the ban was about 1.5 percentage units higher, compared with 1985. Similarly, the age at
25 kg increased by 5-6 days (5). These problems created a demand for antibiotic-medicated feed at therapeutic dosages.
During the subsequent four-year period the use of antibiotics increased, involving up to 75 % of the pigs reared
in 1989. During this time, major efforts were undertaken to introduce sectioning and planned production and to
improve hygiene in the individual herds. Feed was modified and reformulated. The use of antibiotics decreased by
about 50% in 1993 and thereafter a gradual decrease was further supported by the addition of zinc oxide to the
feed. In 1995 only 11 % of weaning piglets were treated with antibiotic medicated feed. (6).
Guidelines on how to prescribe antibiotics as medicated feed were developed (7). It was emphasized that prescription
of antibiotics should always be accompanied by recommendations for prophylactic measures since the need for medicated
feed seems to occur repeatedly in the same units. This was ascribed to housing and management systems, and the
production results were strongly related to the degree of segregated rearing systems and the level of hygiene (8).
New rearing systems were developed, including the weaning of piglets on deep litterbeds in large groups and the
so-called birth-to-slaughter system which is based on production in the same pen from birth to slaughter.
It is evident that the best production result can be gained without the continuous use of AGP. Yet, while many
problems have been solved, others await solutions. The fact that certain pre-ban production results have not yet
be achieved suggests that all pig-producing herds do not currently have optimal conditions for production. Data
from the herds used for evaluation of the ban in 1985-86 have now also been evaluated for the 10-year period 1986-1995.
A comparison of the average values for 1994-1995 with those for 1986-1987 reveals mortality post-weaning to have
decreased by 0.9 percentage units and the age at 25 kg to be reduced by 1-2 days. The losses in production parameters
since the ban have not yet been fully recovered. Today, however, the progressive producers report better production
results than before the ban of AGP.
Egg, Turkey and Specialized Beef Production
Egg Production: Before
the 1986 ban no AGP were used in egg production; thus, the ban did not influence this sector. In addition, animals
are not treated with coccidiostats during the egg production period. Coccidiosis can be seen during the growing
stage and concentrates at farms where the level of animal hygiene is not satisfactory. The availability of a vaccine
against coccidiosis has reduced the need of coccidiostats in floor-raising of laying hens.
1986 the AGP were used in the turkey production solely as a prophylactic agents against necrotic enteritis and
not as a growth promoters. The ban did not result in noticeable clinical problems or reduced growth rates.
Specialized Beef: The use of AGP in specialized beef production
had more or less come to an end prior to ban in 1986 because no positive effects were found. Negative clinical
or other effects as a consequence of the ban have not been reported.
Use of Antibacterial Drugs
The total usage of antibacterial drugs for animals in Sweden prior to and after the AGP ban has been studied in
detail (9, 6, 10). From 1980 to 1984, use of these drugs increased from 41.3 to 50.6 tons of active ingredient
and subsequently decreased by 49% (24,8 tons) from 1984 compared with 1986, when veterinary prescriptions for all
uses of antibiotics were introduced. During this same period, the distribution of antibacterial drugs from the
feed factory decreased by 70%, from 31 to 9.5 tons (Fig 2). The total use of antibiotics slightly increased and
then stabilized (in 1988-1994) at approximately 30 tons of active ingredient per year. This level was approximately
35% below the level before the new legislation was introduced. During 1995 and 1996 antibacterial drug consumption
further decreased to 24.6 and 20.3 tons of active ingredient, respectively. This means that the total use of antibacterial
drugs in animal production has decreased by 55% compared with usage before the AGP ban was introduced.
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ISBN 91-38-20708-7, p 29