7 March 2012

3 minute read

Oceania

The Mackinnon Project Beef Group PDS was facilitated by the Mackinnon Project and is made up by about 16 producers mostly running spring calving herds producing 400-450kg steers at 14-17 months of age.

Increased intensification can, however, come with the increased risk of worm . How this risk is managed often determines the success of the enterprise.

The PDS investigated two animal health issues that can potentially emerge in high production systems - worm control and trace element deficiencies.

Worm resistance to drenches is a major problem in the sheep industry but little is known about the extent of the problem in the beef industry.

Worm drench resistance to all drench groups was shown to be present in cattle herds in Victoria with 50% of properties showing evidence of drench resistance to Ivermectin in the macrocylic lactone (ML) drench group.

Abamectin, a more potent ML, was still effective on farms tested with Ivermectin resistance. About 20% of properties detected resistance to Ivermectin in Small Brown Stomach Worm (Ostertagia), the most pathogenic gastrointestinal worm affecting cattle in south eastern Australia.

There was no difference in the risk of resistance between the spring and autumn calving herds.

Based on these findings and experience with sheep where drench resistance is much more widespread and serious, it is important that producers:

• Understand the resistance status of worms on their cattle properties. While the severity of resistance is low in most cases, producers need to understand how resistance is affecting them and implement a management strategy to minimise the impact.
• Minimise drench use through strategic worm control.
• Consider rotation of effective drench groups, rather than total reliance on the ML group.
• Ensure drench equipment is delivering an accurate dose and that cattle receive a full dose based on bodyweight when drenched.
• Quarantine drench - all new cattle should receive a combination of at least a potent ML plus Benzimidazole (white drench group) and Levamisole (clear drench group) when introduced to prevent introducing drench resistant worms from other properties.

The difference in production, as measured by liveweight gain (based on a typical farm producing about 332kg beef/ha), was up to 26kg/head between good worm control and poor worm control for steers sold at the end of spring and up to an extra 14kg/head for cull heifers sold in late summer.

For a typical 600 ha property in the high rainfall regions of Victoria running 16 dse/ha, this would be equivalent of producing an extra 13kg liveweight/ha (4 per cent increase) and a property with good worm control which would reduce the cost of production about $0.05/kg liveweight.

This study highlighted that the main tool used for monitoring worm burdens (worm egg counts (WEC)) in cattle has very limited value and in some situations can be very misleading as this study found that even when WECs were as low as 50 eggs per gram, substantial growth rate responses were achieved with drenching.

In essence, better tools need to be developed to assist beef producers to decide when to time strategic and non-strategic drenching. The trials also highlighted the gaps in knowledge for producers to make rational decisions regarding when to drench beef cattle, apart from strategic times such as at weaning.

The study also looked at trade element deficiencies in southern production systems.

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