There are no general rules about dosing lambs that can be applied everywhere. Local conditions vary widely and even the situation on a specific farm can change from year to year, depending on the climate. What follows, therefore, are merely guidelines.
The first step is to analyse dung samples to establish the species of roundworm (nematode) on your farm. This will vary from season to season. Generally, however, hairworm is the main problem in the humid summer months, while brown stomach worm and bankrupt worm are more common in the cold months.
Lambs and pregnant ewes are most at risk. Lambs require special attention because they have not yet developed an effective immune system. So it’s crucial to dose them preventively.
A female roundworm may produce 100 to 10 000 eggs per day, depending on humidity and temperature. A farmer must particularly keep an eye open after good rain, on irrigated pasture (moisture and a high stocking rate), at leaking water troughs (moisture and accumulated dung) and at springs and vleis.
The parasite load on the pasture will determine when to dose the lambs for the first time. If the load is high, this is three weeks after the lambs start grazing.
Keep the kraal clean of grass and weeds in which parasites can survive to infect young animals. Move lambing ewes to the farm’s cleanest camps. It is crucial for lambs to obtain natural immunity from colostrum, so immunise the ewes six weeks before lambing.
Conduct a dung egg count test every second year to confirm that your worm remedy is working effectively.
A list of remedies, to be combined if required
As a general guideline, dose lambs for the first time at between five and seven weeks. Use an active chemical that controls roundworm as well as tapeworm; there are a number of options.
Alternatively, use any combination that addresses your specific problem. Ask your vet for advice.
Possible remedies include:
- White remedies (benzimidazole). These have the advantage of healing the stomach wall where worms attach themselves.
- Levamisole, a cost-effective remedy where only roundworm is involved.
- Derquantel/monepantel, a new-generation remedy suitable for a farm where resistance is a problem.
- Praziquantel (releases the scolex, or head), niclosamide (removes segments) and resorantel are registered for tapeworm.
- All of these can be used in combination with one another.
To sum up, the most appropriate remedy to use on lambs depends on combining the results of dung sample tests and dung sample reduction tests with the advice of your local vet. Alternatively, contact your nearest National Wool Growers’ Association office (www.nwga.co.za).
Administering the first dose
- Dose the animals over the tongue, especially in the case of ‘white remedies’ and avermectins.
- Weigh the heaviest lamb and establish the dose accordingly. Don’t simply estimate; it is easy to make a mistake, especially with smaller lambs.
- Administer all doses with steady finger pressure on the dosing applicator. Ensure that the remedy does not enter the lungs – this can lead to lung infection. Work carefully and don’t insert the tube too deeply.
- Use the shorter dosing tube for lambs. Make sure the applicator has been calibrated; the volume is usually low and small lambs can easily be incorrectly dosed. Use a syringe and water to establish the true volume and adapt as necessary.
Administering the second dose
Give a second dose at eight to 10 weeks, taking into account variations from farm to farm and region to region. This is also the time for the first vaccination. Select the appropriate product for your circumstances.
Once again, take dung samples – at least 10 per flock or group. Have these analysed by the nearest lab for roundworm, tapeworm, fluke and coccidiosis. Identify lambs that have been growing poorly (weigh them regularly) and suffer from diarrhoea.
This could possibly be due to brown stomach worm, bankrupt worm, white bankrupt worm, long-necked bankrupt worm, knobworm, flukes and tapeworm.
Bloat in lambs may also be due to tapeworm – watch for voided segments resembling grains of rice in the dung.
Tapeworms may obstruct the intestine where they also compete for nutrients. Coccidiosis can lead to serious diarrhoea. As this is a protozootic disease and not a worm infestation, no worm remedy will help. But registered compounds to control it are available.
Remember that the very best remedy is sufficient milk and feed for the lambs. Ensure that the ewes are well nourished and able to care for their lambs. Without this, remedies are of little use.
Contact Jannie Fourie, NWGA Western Cape, at 083 564 1105 or [email protected].
NWGA presents courses in sheep handling; contact your nearest production advisor for training in your district.