Significant improvement in growth performance in a recent field trial in a Nebraska herd validates use of a single-dose circovirus vaccine in a herd that hasn't experienced clinical disease, says John Waddell, DVM.

Waddell, owner of the Sutton (NE) Veterinary Clinic, explained at a World Pork Expo seminar last month that Ingelvac CircoFLEX from Boehringer Ingelheim Vetmedica, Inc. increased growth rate in a population of high-health pigs that had not exhibited clinical signs of porcine circovirus-associated disease (PCVAD). Culling rate was significantly reduced by vaccination.

The trial herd was diagnosed with subclinical PCVAD. However, vaccination did not greatly alter mortality rate, nor was that an expected result of the producer, Waddell says.

Moreover, performance results indicate “narrowing of the weight range distribution for the vaccinated group of pigs illustrates the biologic and implied economic benefit of immunization (vaccine) for circovirus,” Waddell points out.

Differences in growth performance between the vaccinates and control groups are spelled out in Table 1.

Test Parameters

The field trial was conducted on a farm that was naïve for porcine reproductive and respiratory syndrome (PRRS). During the study, 93 pigs were randomly selected to determine if there were co-infections that might affect health status. Pigs were regularly vaccinated for Mycoplasmal pneumonia, but there were no reported problems of salmonella or ileitis.

Six-hundred, 21-day-old weaned pigs were tagged, weighed and divided into two equal groups. Half of the pigs were vaccinated and the other half served as controls. The two groups were commingled and housed 30 head/pen. Individual weights were recorded at the start of the trial and at Day 35 and 119.

Any pigs that did not reach 180 lb. by Day 119 were culled from the trial, Waddell notes.

Test Results

Vaccination had no major affect on mortality rate, with 3.01% mortality for vaccinates and 3.86% for the control group. Culling rate was 1.34% for vaccinates and 6.69% for the control group.

Polymerase chain reaction (PCR) tests were performed on pigs bled at 3, 6, 8, 12, 18 and 22 weeks, post-vaccination, to check for viremia (presence of infection in the bloodstream). The level of viremia was several times higher in the non-vaccinated pigs entering the finishing phase, Waddell says.

During the 119-day trial, the weight spread or level of variation was much more pronounced in the non-vaccinated group.