Managing parasites for productivity during housing

Housing provides an opportunity to address the range of parasites picked up over the grazing season, to maximise cattle health and productivity over the winter.

The questions of which flukicide to use and when to treat can be challenging, complicated further by the increasing concerns over triclabendazole resistance. Understanding the properties of available flukicides is key to making informed treatment decisions.

Table 1 outlines the active ingredients and formulations available and their spectrum of activity.

Age of fluke vs Active ingredients

What factors should influence product selection?

Adult fluke burdens have the greatest impact on productivity in cattle, and an abattoir study Liveweight gain with flukicidesconducted in Autumn months demonstrated that 97% of the fluke present in cattle livers at this time were late immature or adults with only 3% present as early immature.2 This supports the use of a flukicide targeting the later stages of fluke as an effective approach to treatment at housing.

In another study3, beef cattle were housed and treated with either an ivermectin/clorsulon combination (IVOMEC® Super), or ivermectin (IVOMEC® Classic Injection) plus nitroxynil (Trodax®) or Triclabendazole (Fasinex Cattle oral drench), or ivermectin (IVOMEC® Classic Injection) only. There were no significant differences in liveweight gain between the different flukicide groups, as shown in Chart 2. The study found that flukicide treatment of animals that had positive fluke egg counts at housing resulted in significantly higher weight gain over the 112-day trial period than cattle that were not treated.

It is also worth noting that cattle that were negative for fluke eggs at housing grew on average 20.5kg more than those that were positive, irrespective of treatment, so it is important to remember the other objective of controlling parasites – reducing pasture contamination – and view the housing dose as a way of reducing challenges from parasites next year.
Treating at the point of housing will ensure that animals benefit immediately from production improvements associated with fluke control. Remember, no product is effective down to the very first day of infection: in order to ensure that treatment benefits continue throughout housing and that animals are turned out fluke-free, either test and retreat if necessary or retreat strategically later during housing. The interval for testing/treating will depend on the product used – your vet or SQP can advise on the best approach for your farm.

References:
1. Adapted from Fairweather and Boray, The Veterinary Journal 1999, 158, 81–112
2. MacGillivray F et al., Intern J Appl Res Vet Med 2013. 11(1): 1-6
3. Forbes AB et al., Veterinary Record 2015. 176(13):333

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