How Porcine Ear Necrosis Drains Profits and What New Science Says About Stopping it.

By Matheus Costa, DVM, PhD, DABVP (Swine Health)

Since the 1960s, Porcine Ear Necrosis (PEN) or “ear tip necrosis” was viewed by many producers as an unpleasant but ultimately “cosmetic” issue. It is a condition that appeared a few weeks into the nursery, resulting in disfigured ears, and then stopped progressing as pigs reached the finisher phase.

However, there’s more to it than meets the eye: ear necrosis, like any necrosis, is very painful.

Humans who experienced necrosis reported excruciating pain even with small wounds, which suggests that the welfare of the animals is also affected by this disease. In addition, in a world of social media “virals,” public perception of the pork industry can be impacted negatively quite rapidly when images of pigs with necrotic or missing ears are shared online.

Recent research shows that PEN impacts weight gain and animal performance, but we have also recently learned that it is a preventable issue.

THE ETIOLOGY REVOLUTION: IDENTIFYING THE PRIMARY CULPRIT

Historically, PEN was labeled a “multifactorial disease.” Proposed causes were everywhere, from mycotoxins and high humidity to Staphylococcus hyicus (the agent of Greasy Pig Disease). While these factors may be associated with the disease, they were not the “smoking gun”—i.e., not the cause.

We have successfully reproduced the disease in controlled trials using pure cultures of Fusobacterium necrophorum. This anaerobic, “flesh-eating” bacterium—commonly found in the pig gut tract and manure—is now recognized as the primary cause of PEN.

When skin integrity is compromised through ear-biting or environmental abrasions, F. necrophorum colonizes the site, causing progressive tissue death (necrosis) over time.

THE DISEASE MECHANISM

The progression of PEN is a predictable but dangerous process. Understanding this cycle is critical for identifying where “silent” money is being lost.

This is what we currently know about the disease:

1. Phase 1: The Trigger: The stress of weaning can lead to increased aggressive behaviors, such as ear-sucking or chewing, and fighting. Even microscopic damage to the ear skin provides a route of infection. High stocking densities, poor environmental conditions, and limited feeder space act as catalysts here. Finally, individual “bully” pigs are more likely to “attack” and chew on pen-mates than others.
2. Phase 2: Colonization and Ischemia: F. necrophorum (and secondary opportunistic pathogens like Streptococcus suis or Staphylococcus aureus) enters the wound. The bacteria cause local inflammation and clog small blood vessels of the ear. Because the ear edges have a limited blood supply, these clots quickly starve the tissue of oxygen, leading to the characteristic “black ear” (necrosis and dry gangrene).
3.  Phase 3: The Systemic Breach (The Money Pit): This is where the “silent” costs accrue. The necrotic tissue acts as a reservoir for bacteria. Sometimes these pathogens can then enter the bloodstream (bacteremia) and travel to other parts of the body. Recent studies have confirmed a direct correlation between severe PEN in the nursery and the later development of:
   • Septic Arthritis: Leading to lameness and further ADG (Average Daily Gain) drops.
   • Lung Abscesses: Which may not show outward clinical signs until slaughter.
   • Spinal/Joint Abscesses: Leading to full carcass condemnation at the packing plant facility.

THE “CARCASS ABSCESS” FACTOR

Slaughterhouse surveillance in Canada indicates that abscesses are the main cause of carcass condemnation, resulting in significant economic loss to producers.

PEN is likely an open door to microbes that can cause abscesses, including F. necrophorum and Streptococci.

This is the “hidden” cost: a pig that looks healthy in the finisher but is condemned or trimmed at slaughter, costing the producer the full value of the animal or significant additional grade penalties.

QUANTIFYING THE ECONOMIC IMPACT

To understand why PEN matters, we must also look at numbers.

While a pig with a “mild” lesion (just a small scab) might show negligible growth impairment, the “moderate” and “severe” categories tell a different story.

MANAGEMENT AND PREVENTION: BEYOND ANTIBIOTICS

With the identification of F. necrophorum as the primary bug, the strategy has shifted from “waiting for it to go away” to proactive targeted management.

The Gut-Skin Link: Since F. necrophorum is shed in feces, hygiene is paramount. Gut microbiome modulation can likely reduce the shedding of pathogenic bacteria, subsequently lowering the environmental “load” of the bacteria that cause ear necrosis.

Environmental Engineering:

• Humidity Control: High humidity (>75%) softens the skin of the ear, making it easier for bacteria to penetrate.
• Water Sanitation: Biofilms in water lines can harbor Fusobacterium. Regular acidification and sanitation are non-negotiable.
• Enrichment: Providing toys for oral manipulation (chains, wood) during the first 14 days post-weaning may reduce ear-directed manipulative behavior.

CONCLUSION

Porcine Ear Necrosis is not a minor disease. It is a biological indicator of a production system under stress and a primary source of persistent economic “leakage.”

By focusing on the Fusobacterium necrophorum and addressing the environmental and behavioral triggers that allow it to enter the skin, producers can reclaim lost performance and potentially reduce the risk of costly carcass condemnations.

Matheus Costa, DVM, PhD, DABVP (Swine Health)
University of Saskatchewan

Dr. Matheus Costa is an Associate Professor at the University of Saskatchewan’s Western College of Veterinary Medicine. He investigates the complex interplay between the host, pathogens, and the microbiome. His research targets economically devastating swine diseases, such as Swine Dysentery and Streptococcus suis, employing advanced genomic tools to develop strategies that reduce antimicrobial reliance. With a DVM from Brazil’s UFMG and a PhD from the University of Saskatchewan, Dr. Costa bridges molecular microbiology with practical on-farm applications. He is a globally recognized leader dedicated to enhancing swine health and the longterm sustainability of the pork industry.