Effects of Porcine Epidemic Diarrhea Virus on Sow Herd Reproduction

Megan Inskeep, DVM

Porcine Epidemic Diarrhea virus (PEDv) was confirmed in the United States in May of 2013, and quickly spread across the swine industry. Sow farms affected experienced up to 100% mortality in baby pigs for three to four weeks on average before enough immunity had developed in the sow herd. Nurseries also experienced increased mortality as many of these piglets were weaned at a young age. Loose stools spread through the farrowing house as well as the breeding and gestation barns. Sows were also vomiting and off-feed. With so many sows weaned at one time to get piglets off of milk diets, breeding groups were completely chaotic. Some sows were not cycling very well which further complicated things. It was very clear to see all of these ways that PEDv devastates a sow herd, especially in the first month after becoming infected. What might not be so clear are the downstream effects that PEDv has on a sow farm when it comes to long term sow performance and subsequent litter performance.

Many sows did not lactate for the normal three weeks. In fact, many sows did not lactate at all. There is still so much that is unknown about PEDv and how the animal is affected long term. The different PigCHAMP analysis tools and reports can help tease this information out of the records.

Many farms easily noticed a difference in reproductive performance immediately on the groups that were weaned and then bred during the beginning of the PEDv break and feedback period. For many farms, sows that were weaned and then bred during the few weeks immediately following the PEDv break had lower conception/farrowing rates and fewer total born per sow and pigs weaned per sow. Five farms broke with PEDv between February and May of 2014. The two following charts compare the two breeding weeks (in 2014) following the PEDv outbreak of the five farms to the same two breeding weeks of the previous year (in 2013). As you can see in chart 1, the two breeding weeks following the PEDv outbreak resulted in lower conception rates, with a difference ranging from 2.411.8% within the same farm.

Conception rate pre and post ped

Similarly, total born was also negatively impacted. Chart 2 shows the number of total pigs born per sow for the same breeding weeks used above. Again, all five farms showed a decrease in total born in the two breeding weeks following the PEDv outbreak.

total born pre and post ped

In addition to lower production numbers during those breeding weeks, many farms ultimately culled a significant number of sows, especially younger parity sows from the groups that were weaned during the PEDv outbreak. The circulating virus in the farm affected some sows more than others, and a certain percentage of sows were not able to recover from the side effects. Of the five farms considered for this article, there were 224 parity one sows that were weaned during the PEDv outbreak. Twenty-two of these sows (9.8%) either died, or were culled without making it to their second litter. The majority of these sows were culled for either reproductive issues (mainly returns) or poor body condition.

The charts help illustrate the immediate effects of PEDv on reproductive performance, although most farms did not need to see charts to know how negatively affected these breeding groups were by the current health challenge. However, what the records and charts do help us analyze is if there are any long term effects on the sows after experiencing PEDv. It is well illustrated in scientific literature that a sow’s performance and management during her first lactation help set her up to be reproductively efficient for subsequent farrowings and her lifetime on the farm. Factors that positively influence a parity one animal include proper nutrition/ feed intake, lactation length, and total pigs nursed/weaned. So how are these sows (all parities) affected when they go off-feed during lactation from enteric disease, only nurse pigs for a few days if at all, and nurse very few pigs if any because of 100% pre-wean mortality?

While the answer is still being explored, reports available through PigCHAMP may help dig into this for each individual farm. Reports were run on the five farms previously mentioned above to look at total born for the whole farm on average since the PEDv break compared to the group of sows that were weaned within the three weeks following the PEDv break. That information is revealed in Chart 3. Since many of these sows have only farrowed 1-2 litters since the PEDv break, it is difficult to evaluate the lifelong effect of PEDv on these sows. However, on all five farms, the sows that were weaned in the three weeks following the PEDv break experienced a lower total born than the average for the sow herd as a whole.

total born subsequent farrowing

As time continues and more subsequent farrowing information is available, the effect of PEDv on sows will be more evident. The reports so far suggest that PEDv does have a negative effect on sow performance not only immediately, but also for a sow’s lifetime on the farm. Even though PEDv is an enteric disease, it is important for the industry to consider the reproductive effects of this devastating virus.

Dr. Megan Inskeep, DVM , Megan is a veterinarian at Rensselaer Swine Services in Rensselaer, Indiana. She attended North Carolina State University, where she graduated in 2006 with a Bachelor of Science degree in Animal Science, and a Doctor of Veterinary Medicine degree in 2010, where she focused on Food Animal Medicine. Megan is a member of the American Association of Swine Veterinarians (AASV) and the American Association of Bovine Practitioners (AABP). She is also an active Operation Main Street Speaker. Megan was honored as the “Young Swine Veterinarian of the Year” at the 2015 AASV annual meeting. DR