Living without growth promoters?
The topic of antibiotics in feed continues to swirl in a mess of competing interest groups, politics, and hidden agendas. Several European countries have even banned the use of growth promoting antibiotics. Their experience helps us understand how to maximize production without growth promoting antibiotics.
Growth promotion vs. therapy
First and most important is to distinguish between growth promotion and therapeutic use of feed antibiotics. The treatment of ill animals, either intended for food or as companions to humans, remains an important ethical responsibility for animal owners and veterinarians.
Growth promoters act to improve economic performance of animals. Typically, growth promoters are fed continually at low levels. Most are poorly absorbed and not available for any systemic benefit. Growth promoters “cover up” some of the “restraint” of subclinical infections so pigs get closer to reaching their genetic potential.
Therapeutic feed antibiotics reduce the impact of a clinical disease condition. These products are used in preparation for, or response to, an overt disease, rather than to promote growth. Examples include medication to prevent respiratory disease like the “18 week wall” in finishing pigs.
Continuous vs. strategic use
Growth promoting antibiotics are typically fed continuously. While this may seem simpler, the drawback is added cost and potential overuse of medication. Continuous medication may also inhibit or prevent the development of active immunity. Often these drugs cross over into human medical use, which causes concern about antibiotic resistance.
Therapeutic feed antibiotics are fed at higher rates than growth promoters, but for shorter periods of time. Some therapeutic feed medications are well absorbed from the gut and have systemic as well as enteric activity. Pulsed therapeutic medication (short periods of use separated by periods of non-medicated feeds) has the added advantage of assisting in development of immunity, either through vaccination or uncontrolled field exposure. Non-medicated periods reduce total feed medication costs. In the case of live oral vaccines, these antibiotic-free rations offer perfect times to vaccinate pigs.
Utilizing those drugs that are reserved for use only in animals, such as tiamulin (Denagard
Learning from others
Danish pork producers have lived without antibiotic growth promoters since 2000. There was an initial negative impact from removing growth promoters in nursery diets. Nursery mortality increased and growth rate declined when antibiotics like tylosin, bacitracin, and virginiamycin were removed. Diarrhea and chronic infections like ileitis increased. Feed ingredients had to be managed to prevent edema disease when pigs ate more feed than their intestines could digest. With strategic use of therapeutic antibiotics and improved management techniques, nearly all producers were able to return to normal productivity.
Finishing data showed no performance reduction, consistent with trials in the US showing pigs that received pulsed therapeutic medication performed as well as pigs on continuous medication, but with lower feed medication costs! Total feed medications use in Denmark is now 60% lower. This may also reduce risk of resistance for humans. Most important for the pigs, this helps maintain the beneficial effect of treatment medications in animals, while reducing production cost!
More information
Producing Pork without Antibiotic growth promoters: The Danish experience. Kjelsen N. Advances in Pork Production (2002) Vol. 13, pp. 107-115. www.afns.ualberta.ca/bps
The effect of a metaphylactic pulse dosing in-feed antimicrobial strategy on finishing pig health and performance. Walter D, et al. J Swine Health & Prod 2000; 8(2):65-71. www.aasv.org
Effects of antibiotic regimens on resistance of Escherichia coli and Salmonella serovar typhimurium in swine. Mathew A, et al. J Swine Health Prod 2002;10(1):7-13. www.aasv.org