South East Local Land Services animal health update August 2022

24 Aug 2022

South East Local Land Services District Veterinarians

Your district vet is a source of impartial advice for herd health and welfare concerns on your farm. They provide over the phone advice, property visits and veterinary sampling where required. They work with your private practioner veterinarians, rural resellers and agricultural advisors to provide you with an accurate diagnosis of the cause of disease and treatment and prevention options. The monthly surveillance results share the significant cases seen and reported over the last month.

South East monthly disease surveillance results

Managing worms in weaner lambs: what are the options?

Matt Lieschke, Senior Agricultural Advisor - Goulburn

Managing internal parasites continues to be a major challenge for graziers. With many flocks lambing at present and over the coming months, we need to look ahead and start planning for the next big challenge – weaners. A big part in successful weaner management is preparing paddocks with a focus on both nutrition (for example, pasture quantity and quality) and worms. The below article outlines various options to address both factors, starting with a worm egg count prior to lamb marking.

Worm test prior to lamb marking

Drenching at lamb marking is not normally required, but this is an extreme year for worm risk and it may be warranted in some mobs. To determine if a drench at lamb marking is required, do a worm egg count (WEC) and larval culture on the ewes 10 - 14 days before marking to assess the extent of the problem and give yourself enough time to get organised if drenching is required. Once you have the WEC results back, seek expert advice on whether a drench at marking is needed and what drench to use.

If the WEC results from ewes indicates that the ewes need drenching, then also drench the lambs at marking.

Note: Do not drench lambs in the marking cradle as this increases the risk of inhalation, leading to pneumonia and possibly death. Also, giving lambs the correct dose rate can be difficult due to low volume and large differences in size at marking. Drafting lambs into groups by size/weight is recommended. Always read the product label and work slowly and carefully.

Plan now for weaner worm management

This preparation is best started when lambing commences as paddocks take 3 months to prepare in cooler regions.

Options for preparing weaner paddocks include:

Spelling weaner paddocks – this is good for worm control, but not good for pasture quality and weaners won’t want to go into long grass! Long grass also protects worm larvae (by keeping conditions near ground level moist and protecting larvae from damaging ultraviolet light) and is likely to cause more grass seed issues.

Slash – in addition to worm control, slashing designated weaning paddocks in spring has many other advantages including pasture quality, reducing grass seed issues and enabling the pasture to better respond to summer rain. The main disadvantage is the time involved to slash paddocks. Also, many paddocks are not suitable for a range of reasons (rocks, stumps, holes etc.). It’s important to remember that you don’t need to slash the entire paddock; even just slashing parts of paddocks will help. Stock will graze slashed areas. Slashing a track to watering points is important.
Note: Some producers used a ‘cool burn’ in autumn this year to reduce the overburden of old dead pasture and stimulate new growth. By opening the pasture up, this technique can also make worm control more effective. If you are considering doing a cool burn next autumn, it’s important to slash a good width around the perimeter of the paddock this spring. This area will green up and provide a valuable fire break for when the burn is carried out.

Grazing with cattle – grazing weaner paddocks with cattle is a great option as the worms that affect cattle don’t affect sheep. However, this option will only be available on those properties running cattle, or are set up to run cattle. Target a small number of paddocks and graze with cattle to keep pastures under control.
Note: while most cattle worms don’t affect sheep, there is some limited cross over including T. axei (Stomach hair worm) and Haemonchus placei (the ‘cattle version’ of Barbers Pole worm). Weaner cattle are more likely to contaminate the pasture with these two types of worms – therefore it is best to graze paddocks with adult cattle, or cattle that are at least 12 months of age.
Intensive grazing with sheep – even though grazing with sheep is the least favourable option, some grazing will be required in spring to set paddocks up for weaners.
If you are going to graze weaning paddocks with sheep, it is best to use adult dry sheep (for example wethers). If you are going to graze weaning paddocks with sheep, further contamination must be prevented. This can be done by drenching the sheep with a drench proven to be effective on your property, graze for up to 25 days after the drench and then remove stock from the paddock. If further grazing is required, repeat the process with another mob of freshly drenched sheep.

Fodder conservation –paddocks cut for hay or silage in spring make ideal paddocks to wean lambs into as they will carry very low worm burdens. However, due to the high cost of fodder conservation it’s important to ensure that cutting fodder fits in with your overall farm management plan and you aren’t just doing it for the sake of worm control.

Cropping- cropping allow paddocks to be spelled and removes the plant material that protects the worm larvae, further exposing them to drying and damaging ultraviolet light. A good option for setting up future ‘low worm risk’ paddocks with high quality feed, but good planning and preparation is required. One of the biggest limitations to this strategy will be getting onto paddocks with machinery for spraying, sowing etc.

Wean lambs at 12 weeks

Lambs will start grazing pasture around 4 weeks of age and hence will start picking up worm larvae. Last year there were cases where lambs were dying before weaning due to high worm contamination in lambing paddocks. If worm contamination in lambing paddocks is high, wean lambs around 12 weeks from the start of lambing. If this period is extended to 14 or 15 weeks, it is likely you will see deaths in lambs before weaning.

Weaned lambs require good nutrition to support a healthy immune system and continue to grow. Feeding a supplement to weaners will be important if they don’t have access to high quality green feed, especially if they have been weaned a bit earlier than normal or if weaning weights are down.

Before weaning, don’t forget to ‘imprint’ lambs.

Imprint feeding involves feeding a small amount of supplement (grain, pellets etc) to lambs while they are still on the ewe. Without this teaching process lambs can take up to three weeks to get onto the supplement.

Drench lambs and ewes at weaning

Drench lambs and ewes with an effective drench and move lambs onto a prepared ‘low worm risk’ paddock.

Should I use a ‘long-acting’ drench at weaning?

If you are not confident in your paddock preparation and barbers pole worm or significant scour worm issues are likely, then a drench with sustained action product may be required.
Rather than using a LA product, the other option is to use an effective short acting drench and monitor every 4 weeks.

There are several mid to long-acting (LA) products available, however a lot of these products contain moxidectin. Some properties have reported resistant small brown stomach to moxidectin and we are also seeing increasing resistance by barber's pole worm to moxidectin. If you are going to use a LA drench it’s critical that you use a priming drench and carefully monitor with faecal worm egg counts to ensure resistance is not emerging. It is also recommended to use an exit drench to kill and worms that may have survived the persistent treatment. Further information around the use of LA drenches is available on the Wormboss website.

Keep worm testing

Doing a faecal worm egg count every 4 weeks is the best way to monitor worms. Don’t assume that everything will be fine if you’ve recently drenched a mob. Sadly, there have been cases this year where large numbers of sheep have died 3 weeks after a drench was given. Even if you use a LA product, continue to do worm egg counts every 4 weeks to keep any eye on worms.

Unfortunately it looks like regular monitoring for worms will be required for some time yet, with the Bureau of Meteorology recently raising the La Niña status to ‘ALERT’. La Niña events increase the chances of above-average rainfall for northern and eastern Australia during spring and summer.