The aim of the present study was to compare the effects of oral vaccination and feed medication against Lawsonia intracellularis (LI) on the performance of growing-finishing pigs in a large Hungarian production unit with a high prevalence of LI infection. Pigs testing positive for LI infection were randomly divided into 4 groups and treated as follows:

• Group one: growing pigs (n = 3810) were vaccinated against LI infection after entry into the growing-finishing unit with an avirulent live oral vaccine (Enterisol® Ileitis Boehringer Ingelheim Vetmedica, Inc., St. Joseph, USA).

• Group two: growing pigs (n = 3799) received feed medicated with doxycycline (200 pp. doxycycline hyclate, Primadox® 50, ufamed AG, CH-6210 Sursee, Switzerland) over a 3-week period after entry into the growing-finishing unit.

• Group three: growing pigs (n = 3810) received chlortetracycline hydrochloride (500 ppm), tylosin tartrate (100 ppm) and sulphadimidine sodium (1000 ppm) feed medication (SK 40 ad us. vet., Biokema, CH-1023 Crissier, Switzerland) during a 3-week period after entry into the growing-finishing unit.

• Group four: growing pigs (n = 3809) were not treated.

Culling and mortality rates, reasons for culling and mortality, and average daily weight gain during the entire growing-finishing phase were evaluated. Porcine proliferative enteropathy (PPE) associated culling and mortality rates were lower (1.1%, 1.3% and 1.4% in groups 1-3, vs. 7.0% in the control group, P < 0.05).

Both vaccinated and feed-medicated pigs had lower non-PPE associated culling and mortality rates compared with the non-vaccinated pigs (2.1%, 2.3% and 2.5% vs. 5.9%, P > 0.05). Average daily weight gain was greater (P < 0.05) both in the LI vaccinated and feed-medicated groups of pigs compared with the untreated pigs (799 ± 49 g, 767 ± 48 g and 757 ± 39 g vs. 650 ± 92 g).

The present results indicate that both LI vaccination and feed medication at the beginning of the growing-finishing phase of the production, does not only prevent PPE, but might also result in more resistance and tolerance against other infectious diseases and multifactorial diseases.

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Boehringer Ingelheim Vetmedica, Inc.

November 2006