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Vaccination Effective in Controlling PRRS in Nursery Pigs

by 5m Editor
17 June 2008, at 12:00am

Vaccinating nursery pigs for Porcine Reproductive and Respiratory Syndrome (PRRS) can significantly reduce mortality and improve pig performance, writes ThePigSite senior editor Chris Harris.

These were the conclusions of a three year long study into the vaccination of nursery pigs in a large commercial swine system.

Dr John Waddell from the Sutton Veterinary Clinic in Nebraska told a seminar at the World Pork Expo that most of the current measures to control PRRS are targeted at the breeding herd. However, recent reports from the National Pork Board and Iowa State University have shown that 88 per cent of the costs associated with the disease are incurred in growing pigs.

He showed that PRRS adds $6.01 per pig in the nursery phase and $7.67 per pig in the finishing phase and the National Pork Board figures put the added cost of production caused through PRRS to between $5.60 and $7.60 per pig.

"PRRS continues to be a major challenge for U.S. swine producers, costing them more than $13 per head for losses through the nursery and grow-finish phases," Dr Waddell said.

Dr Waddell showed that the average daily gain was reduced by 12 per cent by the disease and feed efficiency fell by seven per cent, while mortality rose by 166 per cent.

Dr Waddell, who coordinated the research study, said the results help answer one of the major questions producers have about the effectiveness of vaccinating nursery pigs for PRRS.

Due to its virulent nature and the number of strains of PRRS virus in the field, Dr Waddell said that some producers have questioned the ability of PRRS vaccines to provide adequate protection in pigs in commercial production systems compared to results seen in the laboratory.

But he said that vaccination offers a consistent and repeatable protection against a heterologous challenge in the respiratory model.

The study started three years ago when Dr Waddell, in cooperation with researchers from Boehringer Ingelheim Vetmedica, Inc., (BIVI) compared the performance of pigs coming from mixed PRRS-status herds. This included PRRS-negative and PRRS-positive stable, and unstable, sow herds in a large commercial, three-site grow-finish system where average mortality was greater than nine per cent.

In the 2005 study involving more than 600,000 pigs, weaned pigs from PRRS-positive herds were vaccinated with a modified-live virus vaccine soon after weaning at approximately three weeks of age. Mortality rates were compared to pre-vaccination performance in these PRRS-positive nurseries. Growth performance of vaccinated pigs was also compared to non-vaccinated pigs from PRRS-negative herds.

As a result, nursery mortality rates from PRRS-positive/vaccinated nurseries were dramatically reduced and growth rates were improved, resulting in performance equal to the non-vaccinated PRRS-negative pigs.

In 2006, all nursery pigs (513,797 from both PRRS-positive and PRRS-negative sow herds) were vaccinated for PRRS and mortality rates, average daily gain and feed efficiency measured.

Performance of PRRS Positive Vaccinated Nurseries vs PRRS Negative Nurseries - 2005 Annualised Data
Total # Out % Mortality in Wt Out Wt ADG FE
PRRS Positive Vaccinated Nursery 331,462 2.65% 13.73 54.94 0.89 1.56
PRRS Negative Non-vaccinated Nursery 337,810 3.04% 13.61 54.01 0.88 1.62

The results revealed that the performance improvements achieved in 2005 were sustained through 2006.

Vaccination of all nursery flows allowed much greater flexibility in pig flow management by permitting commingling of pigs from more sources. According to Dr Waddell, this facilitated shorter nursery filling times and streamlined pig transportation logistics.

Reid Philips, technical manager for respiratory products for BIVI, said the research study demonstrates the importance of vaccination in managing PRRS virus, especially when the virus is a cofactor with porcine circovirus associated disease (PCVAD).

"Controlling PRRS is a challenging task and requires a systematic approach," Dr Philips said.

"The use of vaccines, along with appropriate biosecurity, pig management and sanitation procedures, sow farm monitoring and PRRS Risk Assessments, is an important part of a comprehensive approach lhal producers can implement to more effectively manage the disease and improve the overall health of pigs within the nursery and grow-finish phases of production."

Dr Waddell told the World Pork Expo seminar that independent confirmation of the vaccination showed an improved daily weight gain, reduction in lung lesions and of clinical disease and a reduction of post challenge viraemia.

"When used properly, vaccine provides consistent and reproducible benefits (statistically) against heterologous isolates," he said.

However he warned that timing is key and that the vaccine needs to be given four weeks before field virus exposure for optimum protection.


Further Reading

- Find out more information on PRRS by clicking here.

June 2008