*Drs. Gil Patterson and Brad Leuwerke are with the Swine Vet Center in St. Peter, Minn.
THERE may have been a time in the not-so-distant past when the presence of Mycoplasma hyopneumoniae (M. hyo) in swine herds was considered unavoidable and something that producers grew accustomed to living with.
However, an increasing number of swine producers have achieved negative M. hyo status on their farms and are enjoying the benefits of improved health and performance.
Those producers that have eliminated M. hyo from their herds employed one of two strategies: a herd antibiotic administration program or a herd closure, which, depending on the porcine reproductive and respiratory syndrome virus (PRRSv) status of the herd, can be done in conjunction with PRRSv elimination. This "piggybacking" of mycoplasma elimination on top of a PRRS cleanup has been successful in ridding farms of two major diseases at once.
These efforts have shown that dealing with M. hyo-associated losses no longer has to be a given and that freedom from mycoplasma pneumonia is an obtainable goal for swine producers.
The concept of an M. hyo-free herd is not new. Initial interest in seriously targeting the elimination of M. hyo began with the development of specific pathogen-free certification programs. These efforts were successful in establishing mycoplasma-negative herds for genetic stock suppliers that practice rigorous isolation, acclimatization, testing and biosecurity in order to remain negative.
As the industry moved toward all-in/all-out and multi-site production and later adopted higher biosecurity standards, maintaining M. hyo-free herds became much more realistic.
In the late 1990s and early 2000s, some of the first reports of successful regional M. hyo elimination began to come out of Europe. Industry collaboration initiatives in both Finland and Switzerland were able to effectively eradicate M. hyo from the national swine population (Baker, 2011; Stark et al., 2004).
Health challenges related to M. hyo cost the industry an estimated $367 million each year. Much of this is lost opportunity due to negative effects on the pigs' rate of gain and feed efficiency, as well as increased mortality, greater weight variability and fewer full-market-value pigs sold.
Nowhere are the losses attributed to M. hyo more noticeable than when mycoplasma-positive herds become infected with influenza or PRRSv. A collection of Swine Vet Center finishing herd data suggested that herds that remain free of both PRRSv and M. hyo outperform mycoplasma-positive herds by approximately 0.05-0.07 lb. in average daily gain and 0.03-0.05 in feed:gain. When a mycoplasma-positive herd becomes infected with PRRSv, these differences increase to a 0.10-0.12 lb. difference in daily gain and a 0.05-0.10 loss in feed:gain.
Consider the additional feed needed to take a 1,000-head finishing barn from a starting weight of 55 lb. to a target weight of 285 lb. (230 lb. of gain) with a 0.1% loss in feed efficiency:
* 230 lb. of gain x 2.78 feed:gain = 639 lb. of feed x 1,000 pigs = 319 tons.
* 230 lb. of gain x 2.68 feed:gain = 616 lb. of feed x 1,000 head = 308 tons.
The difference between the two scenarios is 11 tons, which, at a feed cost of $325 per ton, means $3,575 in additional feed costs.
The time has never been riper for swine producers to get serious about M. hyo elimination. Without a solid solution to PRRSv or influenza at this time, eliminating mycoplasma pneumonia will decrease the severity of these viral pathogens.
Additionally, a majority of genetic suppliers are producing mycoplasma-negative gilts, which makes it difficult to prepare to enter these animals into a mycoplasma-positive farm. Finally, the likelihood of a herd remaining M. hyo negative for an extended period of time is very good, especially if a farm practices good biosecurity, monitors the health status of new herd introductions and, better yet, is filtered.
Understanding the dynamics of how M. hyo is transmitted throughout a herd is critical to its successful elimination. Carrier pigs that are actively shedding the organism are the most common source of reinfection during an elimination program.
Successful herd closures require that all animals be exposed to M. hyo. In unsuccessful eliminations, those gilts that aren't infected become exposed in the sow herd, continuing the bacterium's circulation within the herd.
These gilts' piglets are exposed and will, in turn, shed M. hyo following weaning, leading to flare-ups in the finishing phase. Herd stabilization cannot be achieved until all pigs on the farm have stopped shedding the bacterium, at which point M. hyo-negative gilts can safely be brought into the unit.
To date, the most successful eliminations have occurred after a 240-day herd closure paired with strategic and timely use of appropriate antibiotics just prior to the introduction of test-negative animals.
Herd closure procedures
If space allows, producers should start by loading up the gilt developer unit (GDU) with enough gilts for a 240-day herd closure. Herds that do not have sufficient sow farm and GDU space should discuss the feasibility of an off-site breeding project to provide enough days of closure to occur. This way, ready-to-farrow, mycoplasma-negative gilts can be brought into the farm as soon as the closure period ends.
At the GDU, start mixing the naive gilts immediately with older gilts or low-parity sows from the sow farm that are actively coughing. The more of these "seeder" animals there are, the more likely it is that mycoplasma exposure will occur. Use ropes to obtain oral fluid samples for every pen and room in the GDU, and confirm that all samples are positive for M. hyo on polymerase chain reaction. It is critical that all gilts are exposed before proceeding with the 240-day closure.
Once the herd is closed, vaccinate the entire herd with a mycoplasma vaccine. This should be repeated quarterly before negative gilts are reintroduced. Gilts at the off-site breeding location should be vaccinated for mycoplasma twice before breeding to provide them with extra immune protection. The entire sow farm should be power-washed and cleaned to remove any potential M. hyo-containing fomites. Plan to be conservative with culling decisions so that breeding targets can be maintained with a limited gilt pool.
Six weeks prior to the introduction of new gilts, initiate antibiotic pulses to all sows to help eliminate any shedding that is still occurring. Additionally, all piglets on the farm should be treated with an injectable antibiotic that has activity against mycoplasma. This should be done when treatment to the sows is started and should be continued for another four weeks of farrowing. It is important to make sure all piglets have an antibiotic injection so mycoplasma is not harbored in the farrowing house.
At the end of this period, all animals should have had sufficient time to stop shedding M. hyo, and negative replacement gilts can safely be introduced to the herd.
Simultaneously taking a sow farm to a negative PRRSv and M. hyo status is a huge undertaking, but the end result provides a significant health advantage for the entire wean-to-finish herd. Adding M. hyo to the agenda when deciding to clean up PRRSv on the farm requires some additional time, preparation and input costs; however, the value of mycoplasma-negative pigs is well worth it.
The protocol described has an estimated cost of $6.50-7.00 per sow, while the value of M. hyo-negative pigs is estimated at $1.75-1.90 per pig produced (Baker, 2011). With an increasing number of sow farms pushing 30-plus pigs per sow per year, it quickly becomes apparent that the protocol is time and money well spent.
Baker, R.B. 2011. Mycoplasma hyopneumoniae: A brief review with an emphasis on elimination. AASV Swine Information Library. Dec. 31.
Stark, K.D.C., et al. 2004. Completed eradication of epizootic respiratory diseases in swine in Switzerland. Proceedings of the 18th International Pig Veterinary Society Congress, Hamburg, Germany. Vol. 1.