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The Best Treatments for Pinkeye

When visiting Greg and Jan Judy a few weeks ago, I asked Greg “What do you do about pinkeye?”

“We don’t treat it,” he said. “We found that if we treated it the cow got better in 2 or 3 weeks. If we didn’t treat it, the cow got better in 2 or 3 weeks.”

His response sounds like an old saying I heard from a South Dakota rancher, “You can treat pinkeye and it will get better in a week. Left untreated it will be better in 7 days.”

Causes of Pinkeye

Moraxella bovis is the bacterium responsible for pinkeye and is found in the eyes of recovered and healthy cattle alike. But the bacteria alone doesn’t necessarily cause pinkeye. It seems that there needs to be some kind of added irritation. So flies moving from cow to cow, tall grasses rubbing their eyes, dust and foreign objects in the eye, ear tags banging against the eye, and ultraviolet (UV) sunlight are all considered potential factors in pinkeye. Breeds without eyelid pigment are more susceptible, as are calves, especially bull calves. Adult cattle develop protective antibodies on their eyes’ surfaces, making them more resistant.

Recently, a new strain of pinkeye has emerged: Moraxella bovoculi. Moraxella bovoculi outbreaks are very aggressive and do not respond well to treatment. The symptoms are virtually identical as Moraxella bovis infection. According to Jodi, Kendrew, a British Columbia, Canada veterinarian, “In my own herd, I have had morbidity rates (percentage of the populations with symptoms of disease) of 100%, and animals having clinical symptoms more than once and in more than one eye. Animals severely affected appear to sometimes become carriers, shedding bacteria during times of stress. It is fair to say the Moraxella bovoculi outbreaks in our herd have been equally bad in winter (REAL winter!! NO FLIES) as in summer, and in the summer we noted no difference with fly control vs no fly control.”

In cases of severe outbreaks, Kendrew recommends contacting your veterinarian to discuss diagnostics and treatment options as you may need to handle a Moraxella bovoculi outbreak differently than one caused by Moraxella bovis.

Prevention is the Best Medicine

According to Kevin Gould of Michigan State University Extension, “Management practices that reduce the risk factors associated with pinkeye are the most effective tools in decreasing the incidence of disease.” In addition to gathering information from researchers, I checked in with a number of farmer/rancher listservs to get their ideas.

Pours and Rubs

Gould suggests a variety of pours and rubs to kill and control flies. There are even mineral feeders to help get the insecticide onto animals. On Pasture reader Ben Hartwell has taken this route, describing his set up. “I like any type of portable mineral feeder that effectively gets backrubber insecticide on their face. I’ve used the round rubber ones with the ‘Fly Killer Kover’ which worked for a few years. I currently have two of the Super Heavy Duty mineral feeders made by Tarter.”

This 2:35 video shows the Fly Killer Kover at work:

Managed Grazing

Concerns about insecticide impacts on dung beetles and other beneficial insects mean that many folks will avoid them. If that’s you, take a look at your grazing plan. Rotational grazing that takes into account the 10-21 day fly life cycle and ensures that animals move before the flies find a new host. Think about how your watering sites might add to your problems as well. A Tennessee farmer said keeping cattle from spending too much time around water was a key. “If they have access to a pond, try to stop that because that only makes the flies worse and almost impossible to fight.” His experience was reiterated by many other producers, including Hartwell. “Between the face application, good minerals, portable water, and frequent rotations, I haven’t treated pinkeye in a few years.”

Minerals and Kelp

Ensuring your herd is not deficient in vitamins and minerals is also very important to boost the animal’s immune system. According to Gould, how well an animal works through pinkeye can be influenced by things like “nutritional imbalances, such as deficiencies of protein, energy, vitamins (especially vitamin A if the forage is lower quality) and minerals (especially copper and selenium).” He adds that, “The presence of other organisms such as the infectious bovine rhinotracheitis (IBR) virus, mycoplasma, chlamydia and Branhemella ovis will increase the incidence and severity of disease.”

So how can you get the right minerals to your herd? Many farmers and ranchers, like On Pasture author Tom Kraweic, swear by Kelp. “Kelp Meal is my go to remedy for and prevention of pinkeye. The results have been stunning! Fifteen years ago we had a herd of 950 feedlot heifers arrive with a bit of pinkeye. In a few days there were about 250 infected – a lot to treat! So, I gave Kelp Meal a try. We calculated 8 ounce per head and fed it free choice over three days. After the treatment there were only four animals still infected. I don’t recall where the 8oz dose came from, but it certainly works. I still use Kelp Meal and put it out free choice for a few days if the animals start showing signs of weepy eyes or they are going into tall rank grass.”

I’ll be reviewing Ms. Moore’s paper and sharing more details in upcoming issues of On Pasture. For a head start, you can download her paper here.

Because this method is so popular I looked into trials that might demonstrate why, or whether, this treatment is effective. I found a 2017 paper by Anna Moore at the Kellogg Rural Leaders Programme that said, “It is a widely held belief by Organic American dairy farmers that supplementing kelp into the diet of cattle reduces the susceptibility to pinkeye due to increased Iodine levels in the tears. It was very difficult to find scientific evidence to support this argument. One study that took place last year at the University of Minnesota stated nothing was known about the Iodine concentration in tears and the conclusion was that cattle fed kelp (Ascophyllum nodosum) for 30 days and no effect on Moraxella bovis (M.bovis) bacteria, the main agent that causes pinkeye.”

She does note, however, that although anecdotal, she believes “supplementing calves’ diet with kelp which has over 60 vitamins and minerals would assist greatly in helping to replace valuable vitamins and minerals lost in stressful periods. Because kelp is a plant, it is in a highly absorbable and available form for cattle.


Many producers complain that the vaccines for pinkeye seem to have no more effect than water, and to a degree, they’re right. “The pinkeye vaccine has been disappointing as the sole means of controlling pinkeye,” says Gould. The reason? “There are over 20 strains of the M. bovis bacteria and continuous mutation occurs in the bacteria. While the vaccines contain the most common strains of M. bovis, they do not contain all the strains that occur.”

As For Treatment…

If you don’t go for no treatment at all, antibiotics are the most recommended treatment. Gould recommends tetracyclines at 4.5 cc per 100 pounds of bodyweight injected subcutaneously or in the thin membrane that covers the white of the eye (the bulbar conjuctiva). Sometimes a patch is added to keep the eye from being further irritated. They’re available purchase, pre-glued and timed to fall off in about a week, or you can make your own out of old blue jeans and glue, like another reader suggested.

Some producers say that putting salt in animals’ eyes can cure pink eye. I have found no information that this actually works. One listserv respondent said, “Don’t do it. It just makes the cows mad,” and he suggested, like Greg, to not treat it at all and the animals would get well.

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Kathy Voth
Kathy Voth
I am the founder, editor and publisher of On Pasture, now retired. My career spanned 40 years of finding creative solutions to problems, and sharing ideas with people that encouraged them to work together and try new things. From figuring out how to teach livestock to eat weeds, to teaching range management to high schoolers, outdoor ed graduation camping trips with fifty 6th graders at a time, building firebreaks with a 130-goat herd, developing the signs and interpretation for the Storm King Fourteen Memorial trail, receiving the Conservation Service Award for my work building the 150-mile mountain bike trail from Grand Junction, Colorado to Moab, Utah...well, the list is long so I'll stop with, I've had a great time and I'm very grateful.

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