Stress makes pigs more likely to suffer from a disease which costs farmers in the UK millions of pounds a year in attempts to control, scientists have shown for the first time.
The findings from a study at the Royal Veterinary College (RVC) could influence the conditions that pig herds are kept in to reduce the likelihood of disease outbreaks.
Researchers from the Royal Veterinary College (RVC) were investigating the causes of a complex group of pig diseases, formerly described as post-weaning multi-systemic wasting syndrome, now known as PCV-associated diseases (PCVAD), which can lead to diarrhoea, wasting, respiratory distress and death.
All of these have infection with porcine circovirus (PCV) 2 as common underlying factor and this disease complex costs UK farmers tens of millions of pounds a year.
So far, it was assumed that the development of PCVAD needs PCV2 and a secondary infection for symptoms to occur.
However for the first time the researchers showed that environmental stress from higher temperatures, crowding, or both, can induce symptoms attributed to PCVAD without any secondary infection. PCV2 infected pigs kept in temperatures above the comfort temperatures, or kept in pens smaller than current minimum guidelines were more likely to show reduced weight gain and had higher viral loads than those kept in cooler temperatures or larger pens. These risk factors can occur in herds in the UK.
Professor Dirk Werling, from RVC, who led the project, said:
"Within the initial part of this project, we identified specific risk factors on farms that had an impact on disease severity. Now, we were able to confirm that these risk factors really contribute to severity of clinical signs under experimental conditions. These findings clearly show that sub-optimal management will have further impact on economic losses. We are confident that our findings have a really big impact for the pig industry, given the fact that PCV2 is so common.
"These findings clearly indicate that in addition to vaccination against PCV2, changes in the current farming systems can only be achieved in the long term through a more sustainable agricultural approach, which would involve a less stressful rearing of animals for food consumption. As customers' increasingly prioritise good conditions for livestock, pressure on farmers to produce as cheap and fast as possible might reduce."
The study, published in Veterinary Microbiology was funded by the Biotechnology and Biological Sciences Research Council (BBSRC) 'Combating Endemic Diseases of Farmed Animals for Sustainability (CEDFAS) initiative, with contributions from BPEX, Biobest Laboratories and Zoetis Animal Health.