The Disease That Brings a Flock to Its Knees

Foot rot is the most economically devastating chronic disease in sheep production worldwide, and it is one of the most frustrating conditions I treat because it does not have to exist. Unlike many livestock diseases that are an inevitable part of raising animals, foot rot can be eliminated from a flock entirely — and in many countries, it has been. But elimination requires a systematic approach, not the haphazard treatment-when-you-notice-it approach that most producers default to.

I have worked with flocks where fifty percent or more of the ewes were lame at any given time. Those operations were losing money on every front: reduced feed intake, poor body condition, decreased conception rates, increased lamb mortality from ewes that could not keep up with their lambs, and a chronic antibiotic bill that ate into margins. Every one of those flocks could have been brought under control with a disciplined plan. This article gives you that plan.

What Causes Foot Rot

Foot rot in sheep is caused by the synergistic interaction of two bacteria: Fusobacterium necrophorum and Dichelobacter nodosus. Both organisms are required — neither one alone causes the full disease.

Fusobacterium necrophorum is a normal environmental organism found in soil and manure everywhere sheep are kept. It is an opportunist that invades damaged skin in the interdigital space (the area between the two toes). On its own, Fusobacterium causes interdigital dermatitis (also called scald) — a mild, superficial inflammation between the toes that causes some lameness but does not invade deeper structures.

Dichelobacter nodosus is the true pathogen. It is an obligate parasite of sheep (and goats) — it cannot survive in the soil for more than about seven to fourteen days. Dichelobacter produces proteolytic enzymes that break down the keratinized tissue of the hoof wall, undermining the horn and separating it from the underlying tissue. When Fusobacterium creates the initial interdigital inflammation and Dichelobacter moves in behind it, the result is progressive, invasive foot rot with characteristic undermining of the hoof wall and a foul-smelling, gray-white necrotic discharge.

The Role of Moisture

Both organisms thrive in wet conditions. Foot rot outbreaks are strongly seasonal, peaking during wet periods when interdigital skin stays moist and macerated (softened). Dry conditions — ambient temperatures above 50 degrees Fahrenheit combined with dry ground — suppress transmission because Dichelobacter cannot survive in dry soil and the interdigital skin is intact and less vulnerable to Fusobacterium invasion. This is why foot rot is worse in spring, fall, and any prolonged wet period, and may seem to resolve during dry summer months only to return with the rains.

Lameness Scoring: Measuring the Problem

Before you can manage foot rot, you need to quantify how bad it is. Lameness scoring gives you a standardized way to assess individual animals and track flock-level progress over time.

The 0-5 Lameness Scoring System

  • Score 0: Sound. Normal gait, even weight-bearing on all four feet.
  • Score 1: Slightly uneven gait. Subtle shortening of stride on one limb, may be hard to see at walk but visible at trot.
  • Score 2: Obvious lameness. Clear head bob or shortened stride, but the sheep is still mobile and weight-bearing on the affected foot.
  • Score 3: Severe lameness. Very short stride, obvious reluctance to bear weight, but the sheep can still walk.
  • Score 4: Non-weight-bearing. The sheep carries the affected limb, hops on three legs, or walks on its knees.
  • Score 5: Recumbent. The sheep cannot or will not stand because of foot pain.

Score your entire flock at least monthly. Record the results. The target for a well-managed flock is less than two percent of sheep scoring 2 or higher at any given time. If more than five percent of your flock is lame, you have a foot rot problem that requires systematic intervention.

Treatment: Individual Animals

Hoof Trimming: Do Less Than You Think

This is a point where I disagree strongly with traditional advice, and the research backs me up. The old school approach to foot rot treatment was aggressive hoof trimming — paring away all underrun horn to expose the infected tissue to air. This approach is painful, causes bleeding, creates open wounds that are slow to heal, and actually delays recovery compared to more conservative management.

Current best practice is minimal, therapeutic trimming. Remove only loose, detached horn that is clearly separated from the underlying tissue. Do not dig, do not gouge, do not trim into healthy tissue or draw blood. The goal is to remove necrotic material and allow topical treatment to reach the infected tissue, not to perform radical surgery on the hoof. Studies from the University of Warwick and elsewhere have consistently shown that sheep treated with antibiotics alone recover faster than sheep treated with aggressive trimming plus antibiotics.

Topical Treatment

After minimal trimming, apply a topical antimicrobial. Options include:

  • Oxytetracycline spray (Terramycin aerosol): Convenient, easy to apply, provides a local antibiotic concentration at the site. Spray thoroughly into the interdigital space and over any exposed tissue.
  • Zinc sulfate solution (10%): Apply directly to the affected foot. Zinc has antibacterial properties and promotes keratinization (healthy horn regrowth).

Systemic Antibiotics for Severe Cases

Sheep with lameness scores of 3 or higher, or sheep with advanced undermining of the hoof wall, should receive systemic antibiotics in addition to topical treatment. The most effective options are:

  • Long-acting oxytetracycline (LA-200): 20 mg/kg intramuscularly, repeat in 48-72 hours if needed. This is the most commonly used and cost-effective choice.
  • Tilmicosin (Micotil): Effective but has a very narrow safety margin in sheep — must be given subcutaneously, never IV (IV administration is rapidly fatal in sheep and goats). I use this only in severe or refractory cases with careful dosing.

After treatment, keep treated sheep on dry ground for at least twenty-four hours to allow the antibiotic and topical agents to work before the feet are re-exposed to mud.

Foot Bath Protocol: Whole-Flock Treatment

Foot baths are a tool for whole-flock treatment and prevention, not a substitute for individual treatment of clinically lame sheep. A foot bath alone will not cure an actively infected sheep with undermined hoof wall, but it will reduce the bacterial load on feet across the flock and help prevent new infections.

Zinc Sulfate Foot Bath (Preferred)

Use a 10% zinc sulfate solution (10 kg of zinc sulfate heptahydrate dissolved in 100 liters of water). The foot bath should be long enough that each sheep takes at least four to six steps through it, and deep enough to cover the hooves and interdigital space (minimum three to four inches of solution). Sheep should stand in the bath or walk through it slowly — the goal is at least one to two minutes of contact time. If possible, set up a stand-in bath where sheep remain for fifteen to thirty minutes.

After the foot bath, keep sheep standing on dry concrete or dry ground for at least thirty minutes to allow the zinc sulfate to adhere and act on the hoof surface. Do not turn them out onto wet pasture immediately — the solution will wash off.

Copper Sulfate Foot Bath (Use with Caution in Sheep)

Copper sulfate (5-10% solution) is effective against foot rot organisms but carries a significant risk in sheep: copper ingestion. Sheep standing in copper sulfate may ingest it by licking their feet or drinking from the bath, contributing to cumulative copper load and potential copper toxicity. I strongly prefer zinc sulfate over copper sulfate for sheep foot baths. If you must use copper sulfate, ensure sheep cannot drink from the bath and limit exposure time.

Formalin Foot Bath (5%)

A five percent formalin (formaldehyde) solution is effective but has significant drawbacks: it is a known carcinogen, irritating to skin and mucous membranes (both yours and the sheep's), hardens the horn excessively if used too frequently, and is increasingly restricted in many regions. I no longer recommend routine formalin foot baths when zinc sulfate is available and equally effective without the health risks.

The Five-Point Plan for Foot Rot Elimination

The five-point plan was developed by researchers at the University of Warwick and has been adopted across the UK and internationally as the evidence-based standard for eliminating foot rot from a flock. It works. I have seen it take flocks from thirty percent lameness to less than two percent within two seasons.

Point 1: Avoid — Quarantine and Biosecurity

Every new sheep entering your flock is a potential source of Dichelobacter nodosus. Quarantine all incoming animals for a minimum of twenty-one days on dry ground. Inspect and foot-bath all four feet on arrival. Do not mix new animals with the flock until you are confident their feet are clean. Dichelobacter can only enter your flock on an infected sheep — if you keep it out, you do not have to fight it.

Point 2: Treat — Promptly and Correctly

Treat every lame sheep within three days of onset of lameness. Prompt treatment reduces the duration of infection and the period during which the sheep is shedding Dichelobacter onto the pasture. Use the minimal trimming plus antibiotic approach described above. Do not wait for a scheduled handling day to treat lame sheep — by then, they have been shedding bacteria for weeks.

Point 3: Cull — Chronic and Repeat Offenders

Sheep that have been treated more than three times for foot rot in a season, or that have chronic, deformed feet from repeated infections, should be culled. These animals are reservoirs of infection that re-contaminate pastures and infect flock-mates. Culling chronic offenders is one of the most effective steps in reducing flock-level prevalence, and it is the step most producers are reluctant to take. I understand the reluctance, but the math is clear: one chronically infected ewe will cause more economic damage through ongoing treatment costs and production losses than she is worth.

Point 4: Vaccinate (Where Available)

Footvax is a multi-strain Dichelobacter nodosus vaccine that reduces the severity and duration of foot rot and improves treatment success rates. It is not a standalone solution — it works best as part of the five-point plan, not as a replacement for it. The vaccine is given as two initial doses four to six weeks apart, followed by annual boosters before the high-risk season. Side effects include injection site swelling, so administer subcutaneously in the axillary region (behind the elbow) rather than on the neck or shoulder where carcass damage would matter. Footvax is available in many countries but not universally — check availability in your region.

Point 5: Select — Breed for Foot Health

Foot health has a heritable component. Sheep that consistently maintain sound feet, even during wet conditions and high-challenge periods, have genetic resistance to foot rot. Select replacement ewes and rams from lines with a history of sound feet, and cull lameness-prone animals aggressively. Over multiple generations, you build a flock with inherent resistance that requires less chemical intervention.

Why Over-Trimming Makes It Worse

I want to come back to this point because it is one of the most common mistakes I see. When producers aggressively pare the hoof — trimming deep, cutting into bleeding tissue, trying to "air out" the infection — they cause several problems. First, they create pain and open wounds that take longer to heal than the foot rot itself. Second, they destroy the structural integrity of the hoof wall, making the foot more vulnerable to future infection. Third, they stress the sheep, which suppresses immune function and delays recovery. Fourth, the bleeding tissue they expose is an ideal substrate for Fusobacterium, potentially worsening the infection.

The research is unambiguous: minimal trimming (removing only loose, detached horn) combined with systemic antibiotics produces faster recovery, less pain, and lower relapse rates than aggressive trimming. If your hoof trimmer is drawing blood, they are trimming too much.

Wet Season Management

During prolonged wet periods when foot rot risk is highest, management adjustments can reduce transmission. Avoid holding sheep in muddy lots or laneways for extended periods. Provide well-drained loafing areas with gravel or concrete pads where sheep can stand on dry ground. Increase the frequency of lameness scoring to weekly during high-risk periods so lame sheep are caught and treated early. Consider moving sheep to drier pastures or housing if chronic wet conditions persist.

The Bottom Line

Foot rot is not something you have to live with. It is an infectious disease that can be systematically eliminated from a flock through quarantine, prompt treatment, culling chronic carriers, vaccination, and genetic selection. Stop accepting lameness as normal. Score your flock, treat early, trim conservatively, cull repeat offenders, and keep Dichelobacter off your property through strict biosecurity on incoming animals. A sound flock is a productive flock, and a productive flock is a profitable one.