Pinkeye in cattle: Part Two
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Many approaches have been tried over the years to prevent pinkeye. The random nature of pinkeye outbreaks and the numerous factors that contribute to the disease have led to many myths and misconceptions regarding pinkeye prevention. Management practices that reduce the risk factors associated with pinkeye are the most effective tools in decreasing the incidence of disease. With a lower incidence of disease, the overall concentration of bacteria on the farm will be lowered, reducing the risk of a severe pinkeye outbreak.
Fly control is essential, but can be difficult as face flies are only on the animal for a small percentage of the time. Therefore, addressing the egg and larval stages of the fly as well as the adults is most effective. A moderate to heavy fly infestation is when there are 10 to 20 flies per animal during the middle of the day. A single fly-control program will not work on every farm, so it often takes multiple methods of control to achieve good results. Fly tags, insecticide pour-ons, back rubbers, dust bags and knock-down sprays are helpful in reducing the number of adult face flies on your animals. Fly traps can also be helpful in reducing the number of flies. Feed additives are available that target the maggots that are laid in the manure. Encouraging dung beetles, which break down the manure pat, will also decrease egg survival. Face flies can develop resistance to pesticides over time, so switching the drug class of the pesticides used every year is important. For example, if pyrethrins are used one year, then organophosphates should be used the following year. Waiting until the start of fly season to apply fly tags and removing the old fly tags in the fall also decreases the development of resistance. It is also extremely important to follow the safety precautions recommended by the manufacturer as these insecticides can be toxic to people if handled improperly.
Appropriate grazing, along with clipping pastures will prevent seed-head development, reducing the irritation to the eyes of cattle, as well as reducing the resting areas for the flies. Clipping pastures to a low stubble height in May, just after the seed heads emerge, and again in mid-summer when weeds appear is recommended. Shaded areas need to be available to decrease the ultraviolet (UV) exposure and, in Herefords, breeding for pigmented eyelids has been successful, as this is a heritable trait. A good management program, including an appropriate vaccination program, especially infectious bovine rhinotracheitis (IBR) and bovine viral diarrhea (BVD), good quality nutrition and minerals available at all times will improve the overall condition of the cattle and decrease the incidence of this disease. Overhead hay feeders should be lowered and round bales should be rolled out. Ensuring adequate bunk space will decrease direct contact between the animals. Animals that develop pinkeye should be isolated if possible.
An outbreak is considered to occur when five to ten percent of the animals are affected. The pinkeye vaccine has been disappointing as the sole means of controlling pinkeye because 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. Reportedly, there has been some success when producers have cultured the eyes of their calves and had a vaccine formulated to address the strains of M. bovis that are present on their farm. This generally is only feasible for larger herds, and, as yet, no scientific studies have been done to support this. Vaccines are best utilized when combined with other management strategies.
Check out Part One of this article for pictures and descriptions of each stage of a pinkeye infection.
For additional cattle management resources, visit the MSU Beef Team website.
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