Treating cattle at housing is an effective way to protect productivity over winter and prevent pasture contamination at turnout by reducing worm and liver fluke egg output.
Deciding what treatment to use depends on factors including the species of parasite present on farm, the risk of infection during the grazing period, and the performance of cattle over the summer.
Identify parasites and risk to young cattle
The main parasite species that cause production-loss in cattle are the gutworms Ostertagia ostertagi and Cooperia spp., the cattle lungworm Dictyocaulus viviparus, and the liver fluke Fasciola hepatica. Worms and liver fluke all cause production loss in young animals, making them grow more slowly, and affecting their lifetime productivity.
Grazed youngstock will have come into contact with parasites on the pasture, but the specific challenge will vary according to local conditions, farm history, and animal treatment history.
Before deciding on a treatment, assess the parasite challenge by reviewing the farm history and any treatments given at grass.
Assess cattle performance to identify parasite burdens in youngstock
Monitoring growth and weight gain in youngstock is one of the best methods to identify whether they have a performance-limiting parasite burden. Weighing them regularly will allow their performance to be tracked against targets. Where adequate nutrition is available, but targets are missed, worms are the likely cause.
Where regular weighing isn’t practical, faecal egg counts can provide an indication of the dynamics of worm infection over the grazing season, but provide a less reliable means of assessing worm burdens in individual animals. Blood ELISA tests can detect antibodies to lungworm and liver fluke, while bulk milk ELISA tests can identify antibodies to Ostertagia ostertagi and fluke. Milk tests are more useful in the milking herd, while blood tests can be used for all youngstock. These antibody tests are useful to identify whether animals have faced a parasitic challenge, but will not tell you if they are still infected. Treatment history is therefore important for interpretation.
Choose an appropriate anthelmintic for treating parasites in cattle at housing
Housing is a busy time, so combination antiparasitic products such as IVOMEC® Super (contains ivermectin and clorsulon) offer a practical treatment choice and reduce the stress of handling youngstock multiple times. Depending on the product chosen, a number of internal and external parasites can be treated with one application. However, they should only be used where there is a need to target multiple parasite species. When targeting only gutworms or only liver fluke, choose a single-action product.
Liver fluke treatment is complicated by the emerging resistance to triclabendazole. It is the only flukicide that treats the early immature stage of liver fluke, which causes acute disease in sheep, but does not cause acute disease in cattle. Therefore, it may be appropriate for cattle to be treated with an alternative flukicide such as TRODAX® (contains nitroxynil) or IVOMEC® Super if a combination worm and fluke treatment is appropriate. These flukicide products control the later stages of the parasite and reduce the impact of liver fluke on productivity, while reducing selection for resistance to triclabendazole.
Cattle treated with products that control the late immature and adult stages of liver fluke may need to be retreated at an appropriate interval after the initial housing dose. Diagnostic testing can be used to determine whether a second treatment is necessary.
When selecting a wormer to treat Ostertagi ostertagi at housing, consider whether efficacy against the encysted L4 stage of the worm is required. When young cattle are exposed to a heavy Ostertagi ostertagi challenge late in the grazing period, these worm larvae halt their development in the wall of the animal’s abomasum. Later in the winter and early spring these encysted worm larvae may emerge on mass, causing type 2 ostertagiosis, a severe form of parasitic gastroenteritis which results in significant ill-health, production loss, and can be fatal. The macrocyclic lactones (MLs), such as ivermectin and eprinomectin, are effective against the encysted stages of Ostertagi ostertagi.
Monitor the effectiveness of worm and fluke treatments in cattle
Post-treatment faecal egg counts can help monitor the effectiveness of worm and fluke treatments. The farmer should collect fresh dung samples from 10 individual animals within a group ideally before treatment and, depending on the product used, either seven days (for levamisole) or 14 days (for macrocyclic lactones and benzimidazoles) after treatment. If the results suggest that treatment was ineffective, it should be reported to the product manufacturer and investigated further.
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