Pinkeye in cattle spreads quickly and can turn from a small issue into a problem for the whole herd. It moves from animal to animal through direct contact and flies, especially face flies. That’s why it’s important to spot it early and act fast. What begins as mild tearing or irritation can lead to cloudy eyes, ulcers, or even blindness if not treated right away. Once pinkeye takes hold, it’s much tougher and takes more time to control, so catching it early is your best bet.Pinkeye in cattle usually follows a seasonal pattern. It starts showing up in spring, gets worse in early summer, and peaks when it’s hot and dry. Dust, tall grass, and lots of flies make things worse. Breeds with lighter-colored eyes, like Herefords and Charolais, are more at risk because they’re sensitive to sunlight and irritation. These conditions make infection more likely, so prevention is important.
When pinkeye shows up, treating it can take a lot of work. You’ll need to sort, treat, and keep an eye on sick animals. Even mild cases can get worse if ignored, so separating infected cattle helps stop it from spreading. The main point is this: the sooner you spot and deal with pinkeye, the easier it is to manage. In the next sections, we’ll cover how to prevent outbreaks, what signs to look for, and how to handle pinkeye before it affects your herd’s health and your bottom line.
Why April Is Pinkeye Prevention Month
If you want to get ahead of pinkeye in cattle, start in April—not when you first notice symptoms. By the time you see watery eyes or cloudiness in calves, the issue has often been growing for weeks. That’s why experienced producers use April for prevention, not just reacting.
As spring gets going, several risk factors start stacking up at the same time:
- 🌿 Pastures are growing fast – Taller grass and seed heads can irritate the eye, creating an entry point for infection
- 🪰 Face flies are emerging – These flies spread bacteria from cow to cow, especially around the eyes
- 🌬 Dust and wind increase – Dry conditions and wind-blown debris can scratch and stress the eye
- ☀️ More sunlight exposure – Cattle with light pigmentation are especially sensitive this time of year
As calves get older and more active, they come into contact with each other more often. This extra contact makes it easier for pinkeye to spread.
The main way to prevent pinkeye in cattle is to manage the environment before the bacteria can spread.
Here’s what that looks like in April:
- Start or tighten up your fly control program early.
- Keep pastures from getting overly mature or stemmy.
- Monitor cattle closely for early signs, such as tearing or blinking.
- Make sure your mineral program supports immunity (Vitamin A, Copper, Selenium)
April isn’t when pinkeye is at its worst, but it’s when the groundwork is laid. Paying attention now can save you time, money, and lost performance down the road.
What Causes Pinkeye in Cattle (And Why It Spreads Fast)
Pinkeye is mainly caused by a bacterium called Moraxella Bovis. If a cow’s eye gets damaged, this bacteria can get in and cause trouble.
Common Triggers:
- Face flies – They feed on eye secretions and carry the bacteria from cow to cow.
- Dust & tall grasses – These can scratch the eye, creating the perfect opening for infection.
- Sunlight sensitivity – Cattle with light-colored eyes are more vulnerable.
- Poor nutrition – Vitamin A, Copper, and Selenium deficiency can worsen pinkeye.
Face flies, dust, and tall grasses can irritate cattle’s eyes, making it easier for bacteria to enter. Face flies especially feed on eye secretions and move the bacteria from cow to cow. This shows why controlling flies in your pasture is so important for stopping pinkeye.
Poor nutrition can also make pinkeye worse. Deficiencies in Vitamin A, Copper, and Selenium can lead to more severe cases.
How to Spot Pinkeye Early (Before It Spreads)
Pinkeye in cattle usually develops in three stages. In the first stage, you may see excessive tearing, more blinking, and a bit of cloudiness in the eye. These early signs are easy to miss, so it’s important to watch your herd closely for any changes.
As pinkeye advances to the second stage, the initial irritation tends to worsen. The cloudy appearance of the eye may become more pronounced, and you might start seeing a spreading ulcer across the cornea, with new blood vessels appearing as the eye turns a noticeable shade of pink. In the final stage, the infection can become severe—ulcers may cover most of the cornea, inflammation spreads, and a pus-like substance can form, potentially leading to vision loss or even permanent damage if not treated promptly.
Stage 1 – Early Signs:
- During this stage, cattle will have excessive tearing.
- Will also have an increased sensitivity to sunlight
- Due to the irritation and sensitivity, the cattle will tend to blink more than usual.
- The cornea will develop a slightly cloudy grey appearance due to inflammation.
- It can progress to a small ulcer, which will appear as a small white spot.
Stage 2 – Getting Worse:
- Signs from Stage 1 will continue, but the ulcer will spread across the cornea.
- The eye will become more cloudy.
- Some of the dark colors of the iris can still be seen.
- Blood vessels on the outside portion will begin to grow to make it appear pink (this is what gives the disease its name)
Stage 3 – Severe Infection:
- The ulcer covers most of the cornea.
- Inflammation spreads to the inner part of the eye.
- The inside of the eye will fill with a pus-like substance called fibrin, making the eye appear yellow.
Common Mistakes That Make Pinkeye Worse
Most pinkeye problems in cattle start small and build up over time because of little mistakes that are easy to miss. By the time you see it spreading in the herd, you’re already behind. Knowing what to avoid is just as important as knowing what to do.
Here are some of the most common mistakes producers make with pinkeye prevention and treatment:
- ❌ Waiting too long to treat
Pinkeye rarely fixes itself. Early cases are much easier (and cheaper) to manage. Waiting often leads to more severe infections and spread across the herd. - ❌ Ignoring fly control early in the season
Face flies are one of the biggest carriers of pinkeye. If you wait until fly numbers are high, you’ve already lost ground. - ❌ Letting pastures get too mature
Tall, stemmy grass and seed heads can irritate the eye, creating the perfect entry point for infection. - ❌ Not separating infected animals
Pinkeye spreads quickly through close contact. Leaving infected cattle in the group increases exposure for the rest of the herd. - ❌ Overlooking nutrition and mineral status
A weak immune system makes cattle more vulnerable. Deficiencies in key nutrients, such as Vitamin A, copper, or zinc, can increase the risk.
The bottom line? Pinkeye control is about timing and consistency. Small management decisions—good or bad—tend to snowball. Catch issues early, stay proactive, and you’ll save yourself a lot of headaches (and treatment costs) down the road.
How to Prevent Pinkeye Before It Starts
There are many myths about preventing pinkeye because outbreaks can be unpredictable and caused by many factors. As a result, people have tried lots of different methods—some work, and some don’t.
The best way to keep pinkeye under control is to manage the risk factors. When pinkeye isn’t common, there’s less bacteria around, which lowers the chance of an outbreak.
Fly control in your operation is an excellent first step in controlling this disease. The problem is that face flies live on the animal for only a short time, making it difficult to do this. Taking care of the larval and egg stages, as well as the adult stages, is your most effective strategy. I went over the steps you can take to control fly populations in a previous article, “How do you control flies on cattle?”
Another helpful step is to keep your pastures grazed at the right height. This stops grasses from forming seedheads, which can irritate cattle’s eyes. If grazing isn’t enough, mowing the pasture can help too.
How to Treat Pinkeye (Before It Gets Worse)
It’s important to treat pinkeye in cattle as soon as you spot it. If you catch it early, you can use simpler treatments before it gets worse. Acting quickly lowers the risk of serious problems and keeps treatment easier and less expensive.
The treatment you need depends on how far the disease has progressed. In the early stage, one dose of a long-acting antibiotic may be enough. If the disease gets worse, you might need more medicine and even protective patches to stop further damage. Watching your cattle closely helps you know when to act.
Stage 1
Treating the infected cattle with long-acting oxytetracycline, such as Bio-mycin 200 or LA200, will be very effective at this stage. The recommended dose is 4.5 cc per 100 lbs of body weight, administered subcutaneously or under the skin fold. A second dose given within 48 to 72 hours may increase the percentage of patients who respond to treatment.
It is also recommended that you put a patch over the infected eye. This patch will prevent other irritants from getting in there, thereby preventing the problem from worsening. It will also help with the cow’s increased sensitivity to sunlight.
Commercially available patches will work well for covering the eye. If you do not want to do that, 5″ x 6″ blue jean patches cut to size with glue on three sides, leaving the bottom open, will also work. To ensure that the patch stays on, use cattle backtag cement to glue it in place. Just make sure not to get any glue in the eye.
Stage 2
Treatment for stage 2 pinkeye often continues with the same tetracycline dosage used in stage 1, which helps to control the infection. In addition, a bulbar injection can be very effective—administering a shot into the white part of the eye to target the affected tissues directly. This injection helps to ensure that the medication reaches the specific areas where the infection is causing damage, promoting faster healing and reducing discomfort.
Many producers have had good results using penicillin or dexamethasone in these bulbar injections. Penicillin adds extra antibiotic protection, while dexamethasone helps lower eye inflammation. Both can help with symptoms and recovery, so your choice may depend on your herd’s health and your vet’s advice. Keep a close watch on your cattle after treatment to see how well it’s working and make changes if needed.
Stage 3
At this stage, an oxytetracycline injection and bulbar conjunctival injection will be necessary. You will also need to place an eyepatch. Finally, the third eyelid of the cow will need to be sutured over the eye and closed.
Suturing the third eyelid over the eye will prevent debris or other irritants from entering the eye. It will also make the eye more comfortable, reduce excessive tearing, and possibly shed bacteria.
Another advantage of suturing the eyelid shut is that it supports a fragile cornea, helping to prevent corneal rupture.
Disclaimer: Any suturing should be done by a veterinarian or someone who has been adequately trained to do so, so as not to run the risk of damaging the cow’s eye.
Michigan State has a publication that provides more details on cattle pinkeye if you would like to read more.
Leave a Reply