Key points:
Worms survive less favourably in hot dry conditions. This means that during the recent dry years we have generally not experienced worm issues. A better season in 2010 means that worms may become more of an issue.
Weaners and lambs are the most susceptible class of sheep to worms and management is essential to maximise weaner weight and growth. The immune system of the weaner is not fully developed and the stress of weaning can increase susceptibility to worms.
Low risk paddocks or ‘clean paddocks’ need to be provided to wean lambs on to. These paddocks need to be prepared well in advance using strategies such as grazing cattle, appropriate spelling or through cropping. Paddocks should be spelled for a minimum of 6 weeks and ideally 2 months in which time cattle can be used to graze and manage dry matter availability.
In addition paddocks need to meet the nutritional requirements of weaners or a supplementary feeding program needs to be put in place. Nutrition plays a vital role in the development of the weaner’s immune system and therefore its susceptibility to worms. Weaners being retained as replacements are being supplied with a diet of inadequate protein e.g below 8% it will predispose the weaners, even with low egg counts, to start struggling from January onwards and the effects of worms can be severe by autumn. In prime lamb weaners ensure adequate energy is being supplied in the diet e.g 10-11 MJ ME /KG and ensure they are positively gaining weight.
Worm problems on many properties in July/August can often be traced back to poor worm control in summer/autumn. Therefore it is important that producers have a worm control strategy in place which includes monitoring, grazing and strategic drenching.
If general worm control on the property is good and a clean paddock is available prime lambs should only require a weaning drench. Additional drenching prior to slaughter is usually unnecessary.
If weaners are to be retained a weaning drench should be administered and then a Worm Egg Count (WEC) carried out in December before Christmas. If the count is 100 eggs per gram (epg) or above a summer drench should be administered. A second check should be carried out in February and if the resultant count is 80 epg or above, a second summer drench is required. In May a third WEC check should be done with results less than 100 epg requiring no action.
Using less than fully effective drenches and a combination of poor drenching strategies and methods will not control worms resulting in production losses and further resistance. A drench resistance test should be carried out at least every two years to monitor drench performance.
Worm management in weaners is essential for optimal weaner performance. With monitoring and strategic drenching worms in weaners can effectively be controlled.
Written by Ian Carmichael, SARDI Livestock Systems. For further information go to Wormboss.
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