07/11/2022
Key Points
In order to effectively control internal parasites in beef cattle, producers first need to know which parasites they are dealing with.
Roundworms are the most common and economically important group of internal parasites in beef cattle. Impacts can include reduced appetite and grazing behaviour, depressed weight gains, poor feed efficiency and diarrhea in calves and yearlings; and reduced milk production and reproductive inefficiency in cows. Roundworm larvae cannot survive feedlot environments so it is not a production concern there.
Adult roundworms live inside the gastrointestinal tract of adult cattle, shedding eggs in cattle manure. Eggs develop into larvae which live in pasture grass and are consumed by grazing cattle, causing the cycle to repeat itself.
Cattle under the age of two typically have the highest worm burdens and are most impacted, however internal roundworms are found in adult cattle as well.
Proper pasture management, such as avoiding overgrazing, harrowing only when it is hot and dry, and avoiding use of a pasture in the fall then the following spring, can help reduce worm burdens. Be aware that pastures last grazed by yearling cattle can affect young cattle grazing the following year.
Monitor parasite loads by collecting manure samples so your veterinarian can conduct f***l egg counts.
To reduce drug resistance in parasites, it is important to use the correct product, at the correct time, on the correct class of cattle, at the correct dosage, and then check for effectiveness.
Fall application of ivermectin may not be effective at controlling roundworms. Consult your veterinarian to determine if a spring application of another product such as fenbendazole is necessary to control roundworms.
When introducing new animals to your herd, to minimize the introduction of resistant parasites into your herd, treat new animals with parasite control products from two different classes (i.e. ivermectin and fenbendazole).
Common parasites
Internal parasites, such as roundworms and coccidia, live inside the gastro-intestinal tract whereas external parasites, such as lice and flies live on, or around, the animal. It is important that all parasites are not considered as a single group when planning control measures. Instead, both internal and external parasite control should be considered separately in consultation with a veterinarian, to ensure an overall integrated parasite control program is in place.
Before developing a parasite control program it is important to understand which parasites affect your herd and to what extent.
*Common* *parasites*
Type
Impact on Animal
Roundworms: Brown stomach worm (Ostertagia ostertagi), instestinal worms (Cooperia oncophora and punctata, Nematodirus helvetia**s)
Internal
Roundworms are the most common class of internal parasites in beef cattle and impacts can be insidious. They cause depressed weight gains, poor feed efficiency, diarrhea in calves and reduced milk production and reproductive inefficiency in cows.
Lungworms (Dictyocaulus viviparous). Sporadic disease outbreaks
Internal
Lungworms in upper airways of respiratory system cause nasal discharge, coughing and difficult breathing. It is a sporadic disease in Canada but can be severe affecting both calves and adult cattle.
Fluke (flatworm) (Fascioloides magna)
Internal
Fascioloides magna has a regional distribution (eg. Foothills of Rockies, Great Lakes). It is carried by elk/deer and transmitted in wet boggy areas via semi-aquatic snails. It causes liver condemnation and impact on production poorly defined.
Tapeworms (Monezia benedeni)
Internal
Tapeworms are several metres long and are common. Segments can often be seen in manure but are not considered harmful.
Coccidia (Eimeria bovis, Eimeria zuernii and othe Eimeria spp)
Internal
Coccidiosis is caused by single celled parasites that invade and destroy cells lining the intestine. It is very common parasite causing acute dysentery and diarrhea, neurological signs, chronic diarrhea and reduced growth. Disease most commonly occurs in 1-6 month old calves.
Lice (Damalinia bovis, Linognathus vituli, Haematopinus eurysternus, Solenopotescapillatus)
External
There are two types of lice, biting and sucking lice. Numbers increase with cooler temperatures reaching maximum levels in late winter. Lice cause coat discolouration and hair loss, and sometimes anemia and production loss.
Stable Flies (Stomoxys calcitrans)
External
Typically affect confined livestock, but can also occur on pasture. Bites are painful and often bleed. Pain and decreased production due to reduced grazing/feeding, and animal fatigue from attempts to dislodge insects.
Horn flies (Haematobia irritans)
External
Horn flies congregate around and on cattle at pasture all summer. They bite and suck blood, affecting livestock behaviour, causing reduced performance and reduced milk production.
Cattle grubs (Hypoderma bovis, H. lineatum)
Internal & External
Ivermectin has reduce the prevalence of cattle grubs to very low levels. Adult female flies lay eggs in the hair of the animal which hatch into grubs and migrate deep into the tissues where a painful warble develops that causes pain to animals and holes in the tissue.
