Beef cow parasite control

How are beef herds managed differently from dairy herds?

• All cows should calve within about 60 days

• Degree of confinement varies depending on the time of year

• Calves are mainly the responsibility of the cow

• Calves are raised on pasture

• Calves are weaned at about 200 days

• Cows and post-weaned calves are managed as groups

• Group management allows parasite control to be more targeted

What are the important Endoparasites parasites of beef cattle in Ontario?

• Eimeria spp.

• Cryptosporidium → rarely cause disease

• Hypoderma spp.

• Dictyocaulus viviparus

• Ostertagia → must be on pasture

• Trichostrongylus

• Cooperia

Parasitic gastroenteritis is an important clinical outcome associated with some internal parasites

What are the important Ectoparasites parasites of beef cattle in Ontario?

• Lice

• Horn flies

Which macrocyclic lactones are listed for cattle, and what are their meat withdrawal times?

• Ivermectin → most common

  • Injection: 35 days

  • Pour-on: 49 days

• Doramectin

  • Injection: 40 days

• Eprinomectin

  • Injection: 120 days → only used in spring

  • Pour-on: 0 days

meat withdrawal does not drive selection because the animals are not going to slaughter until months later

What other anthelmintic is available for use in beef cattle for gastrointestinal nematodes?

• Fenbendazole (Safe-Guard) → benzimidazoles

• Internal parasites

• Oral

• Given as a premix

• Meat withdrawal time is 13 days

• Used only for gastrointestinal nematodes (GINs)

What are the key points about lice in beef cattle?

• Lice are common in Ontario

• They are more common on beef cattle than dairy cattle

• High numbers are especially seen on young livestock

• Fall treatment is preventive

• Some macrocyclic lactone pour-ons are sold with a 28-day co-mingling guarantee

• The slide notes that lice may be underestimated by vets but overestimated in significance by farmers

What are the important features of horn fly infestation in beef cattle?

Haematobia irritans

• They are worst in July and August

• They are commonly found on the withers, shoulders, flank, and around the eyes

• Moderate infestations of more than 50 flies per side can decrease weight gain

• Preventive measures commonly used by producers include:

  • Insecticide-impregnated ear tags

  • Backrubbers

  • Insecticide sprays such as permethrin

  • Macrocyclic lactone pour-ons such as ivermectin

• Insecticide resistance may be a concern

When is coccidiosis most commonly a problem in beef calves?

• The most important species are Eimeria bovis and E. zuernii

• It is most commonly an issue in:

  1. Early-born calves, especially February or March calves in yards around April → Giving birth in yards (indoors for the longest)

  2. Calves at pasture in late summer and fall, often around feeding and watering areas

  3. Backgrounding facilities and feedlots, usually within the first month

What are the main features of gastrointestinal nematode infection in beef cattle?

• Exposure increases throughout the grazing season

• Exposure is linked to pasture intake

• Infection tends to occur as trickle infection

• Immunity generally develops quicker than in dairy cattle

• L3 burdens on pasture are generally lower than in dairy cattle

• These parasites often have a subclinical impact

What is the basic timeline for the first year of life in beef calves?

• About 75% of calves are born from February to May in yards

• Calves are turned out to pasture around May 1

What parasite concerns are present in calves during the first part of the first year while they are in yards with their dams?

a) Feb/March calves

• Calves stay in yards with their dams until about May 1

• Cryptosporidiosis is noted as uncommon

• Coccidiosis can be a problem around April

• Even if creep feed is available, calves consume minimal amounts

• Possible group treatment mentioned includes:

  • Long-acting sulfa boluses

  • Toltrazuril (not approved in the US)

b) April/May calves are noted as usually not having coccidiosis as a problem in this context

What parasite control issue is important for first-year calves on pasture?

• Coccidiosis can be a problem in late summer and fall

• It is typically associated with feeding and watering areas

• Creep feed is sometimes provided in the last few months on pasture

• That creep feed may include:

  • Decoquinate

  • Lasalocid

• These may be included for 6 to 8 weeks before weaning

What deworming options are suggested for first-year calves at pasture?

a) If cows were not dewormed, calves can be treated in July

• Ivermectin pour-on is suggested

• February and March calves appear to benefit

• Deworming may not be justified for May and June calves

• The slide questions whether deworming at pasture is required in Ontario

OR

b) Another option is treating cows in the fall with a macrocyclic lactone

• Fall treatment of cows can lead to heavier calves at weaning the following fall

Why are first-year calves treated with a macrocyclic lactone at confinement?

• It is preventive for:

  • Lice

  • Gastrointestinal nematodes, especially Ostertagia

  • Warbles

  • Dictyocaulus viviparus

• Calves are weaned at confinement at about October

• Ivermectin pour-on, such as Ivomec, is commonly used in Ontario

What parasite-control approach is used for calves that remain in confinement until slaughter?

• In backgrounding for 4 to 5 months:

  • Decoquinate may be included in feed for the first month

  • Monensin may be included for the remaining time → for growth enhancement

• In the feedlot:

  • Decoquinate may be included in feed for the first month

  • Monensin may be included for the remaining time

• Clinical coccidiosis is rarely seen if a coccidiostat is used

What is important to remember for second-year replacement heifers at pasture?

• Their grazing history is very different from dairy heifers

• An important consideration is whether all were treated with a macrocyclic lactone the previous fall

When is the optimal time to treat second-year heifers after turnout?

• The preferred timing is 3 or more weeks after turnout

• This is considered optimal if they were at pasture the previous year and treated with a macrocyclic lactone in the fall

• If handling is not possible, treatment can be given via feed, such as fenbendazole

• If handling is possible, a macrocyclic lactone such as ivermectin can be used

When might treatment at turnout be justified in second-year cattle?

• Treatment at turnout could be justified if:

  • They were not treated with a macrocyclic lactone the previous fall

  • Medicating after turnout is difficult

• A drug with residual activity must be used

• If eprinomectin injectable (LongRange) is used, ideally about 10% (random selection) should be left untreated due to resistance

Are two treatments during the grazing season justified for second-year cattle in Ontario?

• Probably not in Ontario, especially if cows are treated in the fall

• Definitely not if eprinomectin injectable is used

• Fecal egg counts may be monitored 4 or more weeks after anthelmintic activity has ended

What is recommended for replacement heifers when they come off pasture?

• Treat with a macrocyclic lactone when they come off pasture

• Replacement heifers usually come off pasture at the end of September

• They have their first calf the following spring

What is the parasite-control recommendation for adult cows in the third year at pasture?

• Treat adult cows with a macrocyclic lactone in the fall → once a year, do not need to treat offspring in grazing season

• This is preventive for:

  • Lice

  • Warbles

• It also helps prevent overwintering of Ostertagia in cows

• This increases weaning weights of calves

• If cows are treated in the fall, the justification for treating calves before housing at the end of their first grazing season becomes questionable