Controlling Internal Parasites In Beef Cattle
Internal parasites live in the digestive tract and lungs of cattle throughout the
world. These internal parasites can result in a very significant economic loss to anyone engaged in beef cattle
operations. Protozoans and worms compete with the animal for the available nutrients and this reduces the animal’s
production, weight gain and milk production. Cattle that are infected with internal parasites are also at great
risk for anemia and other health problems.
Although parasites are often treated in the fall it is
more cost effective and beneficial to treat the animals in both the spring and the fall. This will reduce the risk
of passing the parasites on through waste elimination in the pasture. Treating the cattle twice a year will also
make the pasture a safer area for calves at grazing time.
Parasites that exist internally in cattle have different life cycles. Some of these
worms develop inside the animal and others have a life cycle that must take place in the cattle’s manure. When the
infected manure contaminates food or water sources for the cows the parasites can then spread rapidly. Even the
cold of winter may not kill the larva and eggs that are in the manure. The parasites will often remain dormant
until the next grazing season.
The best way to achieve internal parasite control is to eradicate as many of the
parasites as possible from all of the infected animals. This will help minimize the risk of parasite infection to
calves and other herd members that are parasite free. There are several ways for a beef cattle owner to manage and
control internal parasites.
Lower Stocking Rates
If your herd has high stocking rates it makes it difficult to control and eliminate
internal parasites. Too many cattle grazing on the same land area means that some are forced to use forage that has
been contaminated. Lower stocking rates in a pasture will decrease the spread of infection and reduce the amount of
parasites that come in contact with the animals.
Rotate Pasture Lands
When a pasture is allowed to rest it gives nature a chance to clean and refresh the land.
Parasitic eggs and larvae can be killed when exposed to long periods of uninterrupted sun, rain and fresh air.
Without the requisite host animals the life cycle is interrupted and often terminated.
Utilizing watering systems designed for pastures will give a cattle herd fresh, clean
water that is free from parasitic contamination.
If internal parasites are a pressing concern it may be necessary to treat not only the
infected animals, but the entire herd as well.Beef cattle dewormers come in different forms including pour on
formulas, boluses, feed and mineral additives, pastes, drenches and injectables. There are two basic classes of
products that are used to rid cattle of worms.
• Fenbendazole and Levamisole
• Avermectins (abamectin, doramectin, moxidectin,
Fenbendazole and Levamisole will kill adult parasites and any larvae that may be
present when the treatment is given. The chemicals are quickly eliminated by the cattle and do not interfere with a
future slaughter date. Some parasites can be left alive if they are in a life cycle stage that the chemicals do not
effect. This is why a repeat treatment application must be given within 2-4 weeks from the initial dose.
Avermectins also destroy parasites in the cattle but these chemicals remain in the body
for a much longer period and remain effective during this time. These preparations can kill the parasites more
effectively and do not require frequent administration. Avermectins are more effective at parasite control but they
are also more expensive to buy and use.
When to Treat Cattle for Grubs
Cattle owners can use avermectin class antiparisiticals as a pour on to effectively
control all stages of cattle grubs. Grubs are classified as both an internal and external cattle parasite and they
can be tricky to treat. If the animals are treated when the larvae is in the tissues of the esophagus it can create
bloat. If the cattle are treated when the grub larvae are in the spinal canal the animals can stagger or become
paralyzed. In both cases the animals have a high risk of death. Any cattle treatment for grubs must be done when
the larvae are not in vital tissue areas. A veterinarian can help you plan your internal parasite control