A new approach (acclimatization) has producers inoculating newly arrived pigs with the wild-type strain of the porcine reproductive and respiratory syndrome virus (PRRS) already existing on a farm. The hope is that the pigs will develop specific immunity to that virus and will recover prior to breeding, when the disease takes its toll.
The study found that the approach boosted development and strength of immunity against the local strain, but failed where it counted the most. Pigs exposed to the farm’s virus produced slightly more live births than pigs vaccinated two other ways, but many of these acclimatized animals never gave birth at all and had to be removed from the herd.
"At first we found it encouraging that animals exposed to the wild-type virus, regardless of whether or not they got a subsequent exposure to vaccine, mounted a faster and stronger immune response to the virus than did animals given the modified live vaccine," said Tony L. Goldberg, a professor in the department of pathobiology in the University of Illinois College of Veterinary Medicine.
No positive effect on production was seen when compared with the more traditional approach of inoculations with a commercially available modified live vaccine, he added.
"All things considered, exposure to the existing wild-type virus resulted in a net reduction of 2.45 piglets for each sow introduced onto the farm," Goldberg said. "At this point, though, because of small sample size, the most we can say is that the world still lacks an effective method for controlling PRRS virus in herds where the virus is endemic."
The privately owned farm involved in the study had suffered from chronic PRRS infection for more than five years before the project was conducted in 2003-2004. The study -- funded by the U.S. Department of Agriculture -- was published in the April 1 issue of the Journal of the American Veterinary Medical Association.
For the study, 30 healthy, 70-day-old pigs were brought to the farm and isolated. Soon after that, 20 of the pigs were purposely exposed to the farm’s existing wild-type PRRS strain, while 10 pigs received only the commercially available vaccine. After 42 days, 10 of the pigs that had received the farm-based virus also were inoculated with a killed-virus vaccine, which, unlike the live strains, promotes immunity but doesn’t cause illness.
All of the pigs were allowed to mingle with the other some 800 breeding sows and 7,800 growing swine on the farm. Researchers monitored the experimental pigs for both T-cell activity and antibody production to the virus, as well as recording the pigs’ reproductive outcomes at the end of the study.
"The sample size was small but the magnitude of the effect was large enough for us to detect it with good statistical confidence," Goldberg said. "Seeing 50 percent of animals exposed to just the wild-type strain dropping out of the herd was surprising."
There was no effect on reproductive outcome among the pigs that received both the wild-type live vaccine and the killed-virus strain, Goldberg said.
USDA funding is now covering a larger study on several Illinois farms. "We may be able to generalize more accurately or make some viable recommendations after we’ve have analyzed the new data," Goldberg said.
Jim Barlow | EurekAlert!
Six-legged livestock -- sustainable food production
11.05.2017 | Faculty of Science - University of Copenhagen
Elephant Herpes: Super-Shedders Endanger Young Animals
04.05.2017 | Universität Zürich
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...
23.05.2017 | Event News
22.05.2017 | Event News
17.05.2017 | Event News
23.05.2017 | Earth Sciences
23.05.2017 | Life Sciences
23.05.2017 | Physics and Astronomy