Purdue Pork Page Archive
SEW AND PORCINE RESPIRATORY DISEASE COMPLEX
SEW and PRDC--The discovery and implementation of new technology for the benefit of pigs and producers has always been and probably always will be balanced with the discovery of new problems. Unfortunately, SEW technology has not escaped the development of a list of new problems including a very dramatic presentation of acute pneumonia in 16 to 20 week old pigs. In the early SEW studies, viral diseases were not observed to be clinically evident in nursery pigs. However in one of the studies, PRRSV was isolated from sera of some of the pigs indicating subclinical infection. Dee, et al. have demonstrated the presence of subpopulations of PRRSV infected and noninfected sows in large herds which allowed for occasional shedding of PRRSV to pigs in the farrowing house. This eventually led to outbreaks of PRRS in nurseries. If the subpopulations of PRRSV infected sows result in subsequent transfer of the disease to growing pigs, could not other viruses act in a similar manner and render SEW technology ineffective for prevention of viral pneumonia? Porcine respiratory disease complex has been hypothesized to be caused by PRRSV, SIV, PRCV, and possibly others.These viruses are isolated alone or in various combinations in concert with mycoplasmal or other bacterial infections when PRDC is diagnosed. Dee has observed PRDC occurring in 18 to 20 week old pigs when subpopulations of PRRSV and M hyopneumoniae infected and noninfected pigs are mixed in finishing facilities. We have observed PRDC occurring in SEW pigs in which some pigs were weaned after 21 days and mixed with 13 day old pigs. These pigs developed PRDC when about 16 weeks old. Enzootic pneumonia and possibly SIV (virus not isolated) were the cause of this outbreak. This herd was and remains PRRSV negative. Stevenson (unpublished data) has also observed PRCV as the initiating agent in a PRDC outbreak followed with M hyopneumoniae and secondary bacterial infections. Ongoing investigations of PRDC in large herds using SEW and AIAO production technology will eventually provide information leading to control or prevention of this complex.
For those producers that are having repeated incidence of PRDC, the question remains whether the new technologies are cost effective. Assuming producers enjoy a $10 per head benefit for using SEW technology correctly, how much additional death loss and days to market can be tolerated before SEW is no longer profitable? The morbidity and mortality of PRDC have been reported to be 30 to 70% and 4 to 6% respectively. Using an estimated cost of production of $45 per cwt., an 18 week old pig that weighs 200 lbs. at death would incur a loss of $90. Additionally, PRDC infected pigs would be expected to take an additional 10 days to market, thus adding $1 per pig cost. For 100 pigs, an additional 4% death loss equals a (4x$90) $360 loss plus $100 loss for 10 additional days to market. The total cost of PRDC is $460 or $540 less than the value of using SEW (100x$10 = $1,000) technology to rear the pigs. Treatment costs are not included because reduced medication costs were not used when calculating the benefits of SEW. I would estimate that an additional 9% death loss to PRDC could be tolerated without losing all benefits of SEW to PRDC if preventive measures cannot be developed.
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