It’s a funny thing about walking among beef cattle — I tend to catch things that I wouldn’t otherwise see by staring at them from a truck. Take spotting cattle with pinkeye for instance. The other week, I was walking along with the feedlot manager after the feedbunk was filled. Most of the beef finishers were up to the bunk cable and eating, but about a dozen animals hung back.
I saw that two of these steers had each something wrong with one eye; one animal had an inflamed dripping eye that was closed shut, while the other steer had a visibly cloudy eye. The manager took their ear-tag numbers and treated them that afternoon for pinkeye.
By now, I understand that the patches used to protect their infected eyes have fallen off and both animals are up to the bunk with the rest of the cattle, like nothing happened.
This story is a good reminder that early detection, rapid treatment and a good prevention program should halt the advancement of pinkeye in most cattle herds. We should also be reminded that untreated cattle that go blind in one diseased eye consume less feed and don’t gain as well compared to cattle with acceptable two-eye vision. For example, mid-American research (SDSU, 2013) states spring calves diagnosed with pinkeye weigh about 20 pounds less than normal, which translated in hard cash is about $30 of lost revenue at weaning time.
Even with a pinkeye program in place, some people are shocked when a string of their cattle come down with this highly contagious and painful disease caused by Moraxella bovis bacteria. In itself, the healthy bovine eye has adequate defense mechanisms to prevent M. bovis growth, but a number of factors particularly during the summer months come together that breakdown this natural protection and cause a pinkeye outbreak.
I find it surprising that pinkeye can literarily start with one animal; one eye for whatever reason starts to tear, which underlies the perfect environment for the M. bovis bacteria to thrive. The initial source of eye irritation can come from anywhere such as abrasive pasture grass, dust, wind, or excessive sunlight, yet by far the primary source of cattle eye irritation is the common face fly.
Flies are leading culprits
Face flies are naturally attracted to the head of cattle on pasture, and specifically attracted to the discharges of the eye. These flies have abrasive spongy mouthparts that stimulate the eye to tear, so they can feed off the secretions. Inadvertently, they fly from one individual transferring m.bovis from animals with clinical pinkeye or recovered pinkeye carriers (still harbour bacteria in inner eyelid surface) to healthy cattle. These flies also cause small scratches on the conjunctiva and corneas of the eyes when they feed, which makes it much easier for the M. bovis organisms to attach to the eye tissue and thrive.
Treating cattle infected with pinkeye can be straightforward, but nobody should wait for it to appear before medical action is taken. A sound program for pinkeye prevention may start with insecticidal and non-chemical control, which focuses around the head of the animal as well as takes into account that face flies spend only about 10 per cent of their adult life on the face of cattle. Face flies are usually found spending most of their time on fences, trees and other objects. In the fall, face flies tend to overwinter in cattle buildings.
Pinkeye control program
The underlying foundation of a good pinkeye control programs are:
- Ear tag protection. Plastic ear tags are impregnated with either organophosphates or pyrethroids. One tag per season is recommended per animal. Most people should be aware that the efficacy of the insecticide in ear tags is good for up to about five months of control.
- Strategic rotation of insecticides. It’s also common practice for producers to alternate organo- and pyrethrin-based tags every other year to reduce the chance of face-fly resistance. Note: a new ear tag has come out in recent years that contains both of these insecticides.
- Non-chemical and animal management. Some producers keep their cattle out of tall grass pasture and overgrown bush, which is not always practical, but reduces the incidence of eye irritation. In drylots, excessively dusty areas are controlled by various means. Ideally, infected animals should be isolated from the rest of the herd, because they are highly contagious.
- Nutrition prevention. Make sure nutrients that promote good eyesight and a functioning immune system (such as vitamin A, vitamin E, zinc, copper and selenium) are fed.
- Feed management. I know of one feedlot producer who adds water to his beef grower diet to keep the dust down. Another producer quit emptying dusty feedlot ration on the heads of the cattle during feeding time to avoid irritating feed getting in the cattle’s eyes.
Such methods to halt pinkeye in cattle are important because of the serious economic losses when an animal loses sight of even one eye. Pinkeye might be a summertime disease because of the associated risks involved, but implementing the proper treatment and prevention programs can help producers combat the effects of pinkeye, all year round.