The summer grazingperiod is a crucial time for sheep and cattle production, as farmers strive tomake the best use of grass, the cheapest form of feed. Taking a targeted,informed approach to managing the impact of parasites during this time is vitalto protecting future returns.
The July NADISParasite Forecast, sponsored by Merial Animal Health warns that July and Augustwill be a crucial time for parasite control in lambs. Peak pasture larvaecontamination will occur during the coming months, as lambs developsignificant worm burdens, passing increasing numbers of eggs onto the pasture,and favourable climatic conditions hasten the development of these eggs to theinfective larval stage. The risk will depend on pasture management andtreatments early in the season. Control strategies should take into accountthese farm-level risk factors for maximal effect.
Unmanaged gutwormburdens in lambs can have a negative impact on growth rates, increasingfinishing times and may lead to parasitic gastroenteritis which causes scouringand can result in lamb losses.
Sioned Timothy,veterinary adviser for Merial, says: Worm control in weaned lambs can becomplex, so taking advice on the most appropriate wormer and worm treatment isa good strategy. Discuss your specific farm setup and previous flock managementwith your vet or local animal health adviser (SQP) who will be able to suggestthe best group of wormers for your situation, and how best to incorporate theminto your strategic worming programme.
Targeted wormtreatments based on achieving predicted liveweight gain ensures that only lambs with worm burdens sufficient to impair their growth are treated. Although weighing and sorting lambs may be more time-consuming than grouptreatment, there are considerable benefits; reduced treatments and medicinecosts, and reduced selection for resistant strains of worms, because not alllambs will require treatment. For this approach to be effective, advice shouldbe sought from a vet or SQP on the right product for the flock and parasitespresent.
Implementingtreatment based on faecal egg counts (FEC) can also help achieve a balancebetween reduced selection for wormer resistance and minimizing the productionimpact of parasites. The decision to treat a group should be basedon the FEC result from a pooled sample taken from at least 10 lambs.
Treating the wholeflock or group at regular intervals, without the use of any diagnostic test(liveweight gain or FECs) is not recommended. This approach can reduce theeffectiveness of wormers over time by increasing selection for wormer-resistantstrains of parasites, especially when lambs are grazing relatively safepasture. If this approach is used, measures should be taken to minimize theselection pressure, such as leaving around 10% of fitter animals within a groupuntreated.
Other issuesduring the summer months include tapeworms and blowfly strike. Tapewormsegments are commonly seen in faeces passed by lambs during July and August butare not generally of clinical significance. Blowfly strike is a major risk fromJune onwards which can be reduced through effective internal parasite control,to minimize scouring since this may predispose sheep to blowflystrike.
Strike preventionis the best form of control, says Ms. Timothy. Spray-on products containinginsect growth regulators (IGRs) will prevent infestation, but will not killmaggots that are already present.
Where sheep havealready become struck, farmers should use topical products containing a syntheticpyrethroid (SP), or a diazinon based plunge dip to clear the problem. Theseproducts may also provide protection against blowfly strike and treat otherexternal parasites; farmers should consult their vet or animal health advisorto ensure they are using the most appropriate medicine for the circumstances
In cattle, theNADIS Parasite Forecast reminds farmers to be alert for signs of lungworm inanimals of all ages during July and August, especially in unvaccinated herds.Production losses occur from reduced milk yield in lactating dairy cows,reduced growth rates in youngstock, and the cost of replacements whereindividual losses occur.
Strategic wormingprogrammes using broad-spectrum wormers such as those containing ivermectin(IVOMEC Classic, IVOMEC Super – which also contains clorsulon) andeprinomectin (EPRINEX) to control gutworms, will also help prevent a severelungworm infection, says Ms. Timothy. Achieving a balance between exposure tolungworm larvae to build immunity, and treatment to prevent disease is key toshort and longer-term control of this damaging parasite.
She continues:Lungworm should be suspected in cattle of any age that are coughing at grass,and if diagnosed, farmers will need to treat the whole group. Ivomec classic(injection or pour-on) is suitable for beef cattle and dairy youngstock, whilstEprinex (pour-on) has the benefit of zero milk withhold for adult dairycows.
Incidents ofclinical PGE will peak in cattle during August and September if preventativemeasures have not been implemented. Where young cattle have receiving strategictreatments for gutworm, it is important that they remain set-stocked on thesame pasture for the entire grazing season or are moved to safe grazing, suchas silage aftermath. This will to ensure they are not exposed to additionalworm burdens.