Typically, porcine reproductive and respiratory syndrome, or PRRS, is a seasonal virus in pig herds. It usually spikes between October and April and wanes during the summer months.

But that has not been the last few years. PRRS has persisted through the summer with new strains that seem more severe than usual. In addition to causing the usual reproductive issues, these strains of PRRS have generated a higher rate of mortality in both sows and nursery pigs, leaving many of us in the industry to wonder if the severity of PRRS is going to continue increasing.

Understand the replication of RNA viruses like PRRS
PRRS, much like other viruses in animals and humans, can be transmitted through close contact via the nose, mouth, or through the air. Once inside the pig, it starts attacking the immune cells in the lungs and going head-tohead with the immune system.

If the immune response is not fast enough to take the cells back from the PRRS virus, the immune system will kill off those cells to save the rest of the pig. With fewer immune cells available, this decreases the pig’s ability to fight off additional infections or other diseases, like the flu. As all of this happens, the virus will continue to replicate and spread to other immune cells in the lungs.

Like swine influenza, rotavirus and corona viruses, PRRS is an RNA virus. This means that its makeup consists of a single strand of genetic material RNA, unlike DNA viruses, which contain multiple strands woven together.

Since RNA viruses are made up of a single strand, it’s easier to mutate or make different versions of themselves. These different strains can make it difficult to treat or vaccinate against since vaccines are usually made for a specific strain.

Slow down PRRS in pigs with proven trace mineral nutrition
While there are many preventative methods for controlling PRRS, such as vaccines and improving biosecurity measures, proper nutrition also helps you gain back control over your pigs’ health. In particular, research has shown that zinc slows the replication of viruses.

When a RNA virus replicates, an enzyme called RNA polymerase transcribes viral DNA into more viral RNA, allowing it to spread to other cells. To do this, it needs a divalent metal ion, or metal with a 2+. One example of this is magnesium (Mg2+). Magnesium is still an important nutrient for many functions in a pig’s body, but it must be in the right balance. In this situation, RNA polymerase is like a train, and magnesium is what keeps building the tracks for it to keep going and producing more virus.

However, zinc can replace magnesium, slowing down the production of the tracks and greatly reducing virus replication. The replication reaction inside the cell actually prefers zinc to magnesium. For zinc to be preferentially used in this reaction and impair viral replication, zinc has to be inside the cell. RNA polymerase has a greater affinity for zinc than manganese. If zinc is available, the cells will pull it in to get to work before magnesium gets a chance.

Give pigs an advantage with unrivaled trace mineral absorption
You are giving your pigs an advantage when you feed the right zinc amino acid complex. You are giving your pigs an advantage when you feed the right zinc, a source that is the most metabolically available, which allows more of it to reach the immune cells and help reduce the replication of viruses like PRRS.