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To live with endemic disease — those you can't practically eradicate or keep out of a pig flow — continuous antibiotic feeding has been the traditional mainstay. That's why even with the advent of pig flow management tools like Segregated Early Weaning and multiple site production to reduce the impact of herd pathogens, an estimated 67 percent of finishing feeds still contain antibiotics used in a “continuous” manner — only 5 percent are specifically targeted treatments.

Alternative strategy

One of the alternatives showing promise is “pulse dosing,” a more strategic application of presently available antimicrobials. Pulse dosing specifically targets short-term bursts of antimicrobials at therapeutic levels, to achieve specific health management goals. The advantage to such “metaphylactic” use of antibiotics — in addition to reducing overall antibiotic usage — is that it appears not to suppress the immune response, and thus permits animals to develop some degree of immunity — whether through vaccination or natural exposure.

Results

Two field trials demonstrate the potential effectiveness of the strategy.

• An 1,100-head trial in a commercial three-site Midwestern production system with a consistent history of finisher stall-out due to porcine respiratory disease complex (Mycoplasma, PRRS, influenza virus) at 18 to 22 weeks of age, compared continuous medication vs. pulsed medication vs. no medication. The pulsed medication was Denagard^® plus chlortetracycline given on weeks 2, 4, 7, 10 and 13 post-placement in finishing. The continuously medicated group received the same pulse doses, with 100 grams per ton of chlortetracycline between the pulses, resulting in continuous medication.

  Both pulse and continuous medication outperformed no medication in terms of daily gain, feed efficiency and mortality. Although there were no significant performance differences between pulse and continuous medication strategies — pulse medication permitted animals naturally exposed to Mycoplasma infection to develop their own active immune response, unlike those on continuous medication. That immune response, similar to the one non-medicated pigs experienced, was achieved even while the pulse-dosed pigs were protected from a decline in growth performance. The return on investment of medicating vs. non-medicating was 2.7-to-1 with a net benefit of approximately $3.87 per pig placed.

• In the second trial in an independent operation producing 500,000 pigs yearly, barns were suffering an unacceptably high finishing death loss. Pigs received in the finisher at 10 weeks of age and shipped at 27 weeks of age were either prophylactically medicated with tylosin followed by bacitracin, or metaphylactically pulse-dosed for 10 to 14 days during weeks 1-2, 5-7, and 9-10 with Denagard plus chlortetracycline.

Despite the results being confounded by a swine influenza outbreak only during the implementation of pulse dosing, the pulse-dosing regimen still demonstrated reduction in death loss of 3.8 percent. The Denagard and chlortetracycline pulsing gave the greatest reduction in death loss of more than 20 interventions tested which included other strategies such as various vaccination strategies and changes in pig flow.

More info

Dewey C.; et. al. 1999. Use of antimicrobials in swine feeds in the United States. J Swine Health Prod 7(1):19-25.

Walter D.; et. al. 2000. The effect of a metaphylactic pulse dosing in-feed antimicrobial strategy on finishing pig health and performance. J Swine Health Prod 8(2):65-71.

Moreau I.A.; et. al. 2001. Observations and description of an intervention method affecting death loss rate in all in/all out finishers. Proc Leman Swine Conf 2001:197-200.