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Producers may not realize that a subclinical form of porcine circovirus associated disease (PCVAD) can be lurking in some systems. In these cases, growth performance, rather than mortality, is hurting profitability.

Veterinarians with Kansas-based Cargill Pork, well aware that pigs in a three-site production system were positive for circovirus, watched PCV2 virus routinely spike in blood samples from pigs at 10 weeks of age. Yet there was no clinical expression of the disease.

Calling the appearance of the circovirus infection “subclinical”, the Cargill veterinarians conducted a study using Ingelvac CircoFLEX. Their objective was to see if vaccination for subclinical PCVAD had biologic and/or economic benefits.

The three-site production system chosen for the study was negative for PRRS and positive for Mycoplasma hyopneumoniae and PCV2.

Pigs from three sow farms were vaccinated at weaning, about 21 days of age, and commingled in the nursery. A total of 1,200 pigs were placed on test – 600 vaccinates and 600 controls.

Grouped by size and sex, pigs were placed 25 or 50 per pen. Every other pig was vaccinated with a 1 mL dose of Ingelvac CircoFLEX and individually weighed. Pigs were individually weighed again on Day 41 prior to being moved to a finishing barn and again on Day 131 at the end of the study.

Blood samples were drawn from one vaccinated and one control pig from half of the pens five times and submitted to the Boehringer Ingelheim Health Management Center in Ames, Iowa, for serologic and PCR testing. Finally, 509 vaccinated and 474 control pigs were evaluated at the slaughter plant for various carcass traits.

Economic benefits were calculated based on total live weight delivered to slaughter and the relative market value of pig weight classes. Pigs exceeding 255 lbs. live weight were valued at $51 per hundred pounds while lighter pigs were valued at $31 per hundred pounds.

PCVAD was confirmed histologically in individual pigs, but groups were considered clinically normal throughout the evaluation, confirming the presence of subclinical PCVAD.

Results of the Cargill study1, presented during the American Association of Swine Veterinarians annual meeting in March 2008, showed the following:

• Vaccinated pigs had reduced PCV2 viral loads at 10, 14 and 18 weeks post-placement, confirmed through PCR.
• There were no differences between the two treatment groups for average daily gain Day 0-41 during the nursery phase.
• Vaccinated pigs had improved Day 41-131 average daily gain and Day 0-131 daily gain compared to non-vaccinated controls.
• There were no significant differences between the two treatment groups for either nursery or finishing mortality rate.
• Vaccinated pigs had a significant reduction in bottomend pigs as demonstrated by the number of pigs weighing less than 180 lbs at day 131 compared to non-vaccinates.
• Vaccinated pigs had heavier hot carcass weights and a more muscular carcass with greater depth of loin muscle.
• Hot carcass weights averaged 194 lbs. for vaccinates and 190.8 lbs. for control pigs.
• In terms of total live weight delivered for slaughter (including culls), vaccinates produced 5,805 lbs. more pork than controls.

Study results also reported no adverse local or systemic side effects attributable to vaccination.

Vaccinates earned about a 1 percent premium in value relative to controls at the packing plant. The total market value of vaccinates and controls, including culls, was determined by factoring in additional revenue based on the packer market grid matrix.

estimate was calculated of $4.38 return on investment for every dollar invested in Ingelvac CircoFLEX vaccine.

As a result, those involved in the study conclude significant biologic and economic improvements were achieved by controlling the subclinical impact of PCVAD by vaccination.

Reference: 1. Biologic and economic benefits of controlling subclinical PCVAD with vaccination, Doug King, DVM, Paul DuBois, DVM and Tom Painter, DVM, of Cargill Pork, Wichita, KS; Tyler Holck, DVM, Roy Elder, Cammie Johnson and Edgar Diaz, DVM, of Boehringer Ingelheim Vetmedica Inc., Proceedings, American Association of Swine Veterinarians, March 2008.