Pink eye in cattle is treated with injectable antibiotics, most commonly long-acting oxytetracycline given as a single shot under the skin. Early treatment is critical because the infection can progress from mild tearing to a deep corneal ulcer within days, potentially causing permanent blindness in the affected eye. Beyond antibiotics, a combination of eye patches, fly control, and pasture management gives cattle the best chance at a full recovery.
Recognizing Pink Eye Early
Pink eye, formally called infectious bovine keratoconjunctivitis (IBK), typically starts with excessive tearing, squinting, and redness of the whites of the eye. Within a day or two, a small white spot appears on the cornea. That white spot is an ulcer, and it can expand rapidly to cover most of the eye’s surface. In advanced cases the cornea turns completely opaque, the eye may rupture, and the animal loses vision permanently.
The earlier you catch it, the faster it resolves and the less tissue damage occurs. Calves and young stockers are hit hardest, but any age group is susceptible. Animals that are squinting or holding one eye closed in bright sunlight are the ones to pull from pasture first.
Injectable Antibiotic Treatment
The standard treatment is a single dose of long-acting oxytetracycline (the 200 mg/mL formulation) at 9 mg per pound of body weight, given subcutaneously. For a 500-pound calf, that works out to roughly 22.5 mL. This single injection maintains therapeutic levels in the tissues long enough to clear most infections without repeated handling. Beef Quality Assurance guidelines recommend subcutaneous injection over intramuscular to reduce carcass damage.
Your veterinarian may also recommend a subconjunctival injection, which places a small volume of antibiotic directly under the membrane covering the eye. This is done with a 25-gauge or smaller needle, and the total volume is typically 1 mL or less. It delivers a high concentration of drug right at the infection site, which is especially useful for more advanced ulcers. This technique requires proper restraint in a chute and some comfort with the procedure, so work with your vet the first time.
All antibiotics used in cattle require veterinary oversight. Under the FDA’s Veterinary Feed Directive framework, using medically important antimicrobials without authorization from a licensed veterinarian is illegal. You need a valid veterinarian-client-patient relationship, which means your vet has examined or visited your animals and takes responsibility for clinical decisions about their health.
Why the Bacteria Matters
Two closely related bacteria cause most pink eye cases: Moraxella bovis and Moraxella bovoculi. They don’t respond to antibiotics the same way. Research comparing the two species found that M. bovis consistently required higher antibiotic concentrations to be killed, while M. bovoculi was more susceptible across most drugs tested. Among M. bovis strains specifically, 40% showed resistance to penicillin and 20% showed resistance to oxytetracycline. Only 9% of M. bovoculi strains were resistant to penicillin.
This matters practically because if you’re treating cases that aren’t responding to oxytetracycline, the pathogen involved may be a resistant strain of M. bovis. Talk to your vet about culturing the bacteria from an affected eye so you can choose the right antibiotic rather than cycling through treatments that aren’t working.
Eye Patches Speed Healing
Applying a cloth eye patch after treatment is one of the most underused tools for managing pink eye. A controlled trial in stocker steers found that patched eyes healed in a median of 10 days compared to 14 days for unpatched eyes. Statistically, patched eyes were 62% more likely to heal at any given time point during the study.
Patches work on multiple levels. They block visible and ultraviolet light, which relaxes the iris and reduces painful spasm inside the eye. They also physically block face flies from landing on the infected eye, which slows transmission to other animals in the herd. Commercial cattle eye patches are glued to the skin around the eye socket, with the bottom edge left unattached so fluid can drain. Reinforcing the edges with duct tape helps keep the patch on longer, since glue alone often fails within the first day or two.
Controlling Face Flies
Face flies are the primary vector spreading pink eye through a herd. They feed on eye secretions, picking up bacteria from an infected animal and depositing them on the next one. Treating individual cases without addressing flies is like bailing water without plugging the hole. The treatment threshold is 10 or more face flies per animal.
You have several delivery methods to choose from, and using the right one depends on your operation:
- Insecticide ear tags: Two tags per animal provide season-long control. Remove them at the end of fly season or when they stop working. Rotate the insecticide class every year to prevent resistance buildup.
- Backrubbers: Effective against face flies when used with face fly attachments. Mix the insecticide with mineral oil or fuel oil, and recharge as needed. Forced-use setups (placed where cattle must pass through, like at water or mineral stations) work best.
- Dust bags: Some formulations kill face flies when hung in forced-use locations. Use in pairs for best coverage and recharge throughout fly season.
- Pour-ons: Formulations that allow face application will control face flies directly. Most provide two to four weeks of control before reapplication is needed.
- Oral larvicides: Fed as mineral additives or boluses, these pass through the animal and kill fly larvae developing in manure, reducing the next generation of flies on pasture.
Rotating between chemical classes (pyrethroids, organophosphates, and macrocyclic lactones) from year to year is essential. Fly populations develop resistance quickly when exposed to the same class season after season.
Pasture and Environment Management
Tall, mature grass with seed heads at eye level is a classic trigger for pink eye outbreaks. The seed heads scratch the cornea as cattle graze, creating micro-abrasions that give bacteria an entry point. Clipping pastures to keep grass below eye level during peak fly season reduces this mechanical irritation significantly.
Dust, pollen, and UV radiation also irritate the corneal surface and disrupt the eye’s natural defenses. Providing shade structures or access to tree lines helps on multiple fronts: it reduces UV exposure and gives cattle a place to congregate away from the worst midday sun, when flies are most active. Keeping feeding areas clean and dry minimizes dust exposure. Good nutrition and high-quality forage support immune function, which in turn helps animals resist or recover from infection faster.
What About Vaccines?
Pink eye vaccines are widely available but their track record is disappointing. A five-year randomized trial involving nearly 1,200 calves compared three groups: one receiving an autogenous vaccine (custom-made from bacteria collected on that operation, including both Moraxella species), one receiving a commercial M. bovis vaccine, and one receiving a placebo. The autogenous vaccine group had a lower cumulative pink eye rate (24.5%) compared to the commercial vaccine group (30.1%) and the placebo group (30.3%), but the differences were not statistically significant. The autogenous vaccine also produced stronger antibody levels, yet those antibody levels did not correlate with actual protection against the disease.
This doesn’t mean vaccines are useless in every situation, but it does mean you shouldn’t rely on vaccination as your primary prevention strategy. Fly control, pasture management, and early treatment of active cases will do more to reduce losses in your herd than any currently available vaccine.