Research work carried out by Department of Department of Primary Industries and Regional Development (DPIRD) researchers some years ago demonstrated that summer drenching programs provide good worm control in beef yearlings under Western Australian conditions. Weaner cattle remain the most vulnerable animals to parasites on the farm. The table below is designed to pin point the time in the management calendar when drenching for the different classes of cattle on the farm are best carried out.
| Time of year | Weaners | Bulls | Calving heifers | Mature cows | Suckling calves |
|---|---|---|---|---|---|
| Weaning (December - January) | Yes (check WHP and ESI) | Yes | No | No | No |
| Pre joining (March - May) | Only where severe parasite problem in past years | Yes | N/A | No | No |
| Pre calving (February - March) | No | No | Yes (some mobs may benefit) | No (individual cows with signs only) | No |
Please note:
- calendar dates will vary slightly depending on location
- individual cows with signs of worms justify a drench at anytime of year
- no drench required for calves at calving or marking
Drench resistance
Drench resistance is now known to be present in WA. A recent survey indicated that ivermectin (macrocyclic lactones) resistance was detected in the hair worm (Cooperia oncophora) and present on two-thirds of farms. Importantly, ivermectin was fully effective against brown stomach worm (Ostertagia ostertagi). The white and clear drenches were fully effective against hair worms but resistance was present against brown stomach worm on about half of the farms tested.
These results present good evidence for use of combination products to fully control the parasites of cattle and to prevent further progression of the resistance situation. Currently there is at least one combination registered for use in cattle in Australia.
Lice control
Cattle may carry both sucking and biting lice, but these usually do not detract from growth rates unless infestations are heavy. Heavy infestations usually occur when animals are in poor condition and lice populations are able to build up in cold weather. In these cases, it is important to check that nutrition is adequate, and consideration then given to a whole herd treatment. Generally there is no need for a regular yearly lice treatment, even though lice may be on the property. Only specific spray on treatments registered for lice will give complete removal, while drenches will control but usually not eradicate lice, so regular herd drenching to control lice is not warranted.