Two of Australia’s largest animal health companies, Coopers Animal Health and Boehringer Ingelheim, have submitted the items below for publication, discussing their respective drench products and worm resistance. Editor.
COMBINATION drenches can not only help southern beef producers prevent the development of worm resistance on their properties, but can also deliver measurable production benefits, a recent trial has suggested.
Conducted by Charles Sturt University in collaboration with animal health product manufacturer Boehringer Ingelheim, the trial compared Boehringer’s Eclipse Combination Pour-On against single-active macrocyclic lactone (mectin) drenches on six beef cattle properties in southern NSW. A total of 550 weaner steers were involved.
At the start of the trial, weaners were weighed and allocated to one of two treatment groups, to receive either Eclipse Pour-On or a single active pour-on.
Egg counts were taken and weights recorded ten days after treatment and then every 30 days for three months. Eclipse demonstrated a statistically significant advantage over the single-active (mectin) treatment on two of the six farms, a summary released by Boehringer Ingelheim said.
On average across all six trial sites, at the end of the trial weaners treated with Eclipse were 5kg heavier than those treated with single active.
Lead researcher Professor Bruce Allworth said the trial found resistance to the single-active mectin drench on five of the six farms. Eclipse was effective on all six properties, with an estimated efficacy greater than 99 percent, the summary said.
“Producers are not always aware of the significance of the production risks to younger cattle. This research demonstrates the risk of treatment failure for the first time in Australia,” Prof Allworth said.
He suggested even greater weight differences in favour of Eclipse-treated weaners might be expected depending on seasonal conditions.
“Worm burdens usually peak during winter, but 2017 had a relatively dry winter so the worm count was not as high as it might have been,” Prof Allworth said. “The results may have been more pronounced in a tougher winter season.”
One of the researchers involved in the trial, Dr Brad Goonan, a veterinarian at Murray Valley Veterinary Services, said worms were particularly problematic in cattle at the age of the trial animals – around nine to 15 months.
“Younger cattle are particularly vulnerable to worms as they have recently been weaned, so they only have a few months’ exposure to worms via the pasture. Their systems have not built an immunity to worms, and this is a peak time for their development,” Dr Goonan said.
“It’s a time when young cattle are trying to grow and develop. We’re aiming to give them the best chance, and using an effective drench helps them develop into well-grown and healthy cattle.”
One of the farmers who participated in the trial said that most cattle producers were conscious of the link between worms, weight and profit.
“You want them to be in their prime. Because they’re growing, worms can set them back – they just don’t do as well. They probably feel a bit crook, don’t eat as much and don’t put as much weight on,” he said in Boehringer Ingelheim’s summary.
Lead researcher Bruce Allworth said now was the ideal time for producers to look more closely at their drenching regimen.
“At the moment, returns on cattle are reasonable and steer prices remain strong. It’s a good time for producers in susceptible areas to implement best practice, including monitoring worm burdens, assessing their drench usage and testing for resistance on-farm,” he said.
“Using a combination drench will help producers make the most of a strong market by potentially optimising weightgain, and at the same time it is likely to be the best strategy to combat drench resistance,” Prof Allworth said.
Farmers, for many years, have relied on drenches for worm burdens in their cattle, says Coopers Animal Health ruminant technical advisor, Michelle Dever.
This has been a very successful management strategy in the past, however recent reports have shown an increasing prevalence of drench resistance on cattle farms in Australia1,2,3.
Worms cost the Australian Cattle Industry about $94 million/year4. Production losses can occur without any obvious external signs that cattle are ‘wormy’. Reduced growth of 20-30 kg has been shown in young cattle when worm control has not been managed well5.
There is widespread resistance of the three major worm species (Ostertagia ostertagi, Trichostrongylus spp. and Cooperia spp.) to each of the three drench groups (macrocyclic lactones (ML), benzimidazoles (BZ) and imidazothiazoles (LEV)).
Two recent drench surveys conducted in southern Victoria and in the Macalister Irrigation District of Gippsland, Victoria reported 90pc and 100pc of farms respectively had resistance to at least one drench active3,6. On farms where a triple oral active (ML+BZ+LEV) combination (Trifecta) was administered, no resistance was observed7,12. These findings are in agreement with confirmed ML resistance on dairy farms in southern QLD2 and on beef properties in WA1. Recent work undertaken by Coopers Animal Health in northern NSW and southern QLD has shown 80pc of the farms tested had ML resistance; while fenbendazole, levamisole and the combination drench, Trifecta® all remained effective on these farms7.
What has led to the emergence of drench resistance on cattle farms?
Until recently, combination drenches were not available for use in cattle and there has been a heavy reliance/overuse of ML based drenches.
MLs are routinely used to treat both internal and external parasites and while this is considered advantageous there is a risk of increasing selection pressure for development of resistance against non-target species. As ML resistance emerged, there were reports of variability of pour-on and injectable ML drenches to consistently deliver high efficacy.
A study involving 14 farms in New Zealand8 investigated the efficacy of moxidectin against worms when administered to cattle as either an oral, injectable or pour-on formulation. Overall, a significantly greater reduction in worm egg counts with less variation was observed following treatment with moxidectin oral (91.1pc) compared with treatment with moxidectin injectable (55.5pc) or with moxidectin pour-on (51.3pc). It was postulated that ‘oral administration of ML’s results in a higher concentration of the active reaching the target worms’8.
Use of combination drenches
Combination drenches are most likely to provide adequate efficacy against worm populations that include several resistant species, whilst also reducing selection pressure for development of drench resistance9. Increasing the number of actives within a drench, with similar spectrums of activity but different modes of action, is likely to reduce the rate at which resistance develops10,11. Trifecta is the only triple active combination (abamectin, levamisole and oxfendazole) commercially available for use in cattle.
Best practice strategies to delay the development drench resistance:
1 Cotter JL, Van Burgel A, Besier RB (2015), ‘Anthelmintic resistance in nematodes of beef cattle in south-west Western Australia’, Veterinary Parasitology 207, 276-284
2 Lyndal-Murphy M, Roger D, Ehlich WK, James PJ, Pepper PM, (2010), ‘Reduced efficacy of macrocyclic lactone treatments in controlling gastrointestinal nematode infections of weaner dairy calves in subtropical eastern Australia’, Veterinary Parasitology 168, 146-150
3 Rendell DK, Homer D, Rolls N, Webb-Ware J, Cotton S, Beall B, Larsen J (2014), ‘Anthelmintic resistance in cattle nematodes on thirty-six Victorian properties’, Proceedings of the 28th World Buiatrics Congress 231–244
4 Lane J, Jubb T, Shephard R, Webb-Ware J, Fordyce G (2015), ‘Priority list of endemic diseases for the red meat industries’, B.AHE.0010. Meat & Livestock Australia Limited, Sydney
5 Eppleston J (2011), ‘Managing the growth of weaner cattle: The impact of internal parasites’, B.AHE.0010. Meat and Livestock Australia Limited, Sydney
6 Bullen SL, Beggs DS, Mansell PD, Runciman DJ, Malmo J, Playford MC, Pyman MF (2016), ‘Anthelmintic resistance in gastrointestinal nematodes of dairy cattle in the Macalister Irrigation District of Victoria’, Australian Veterinary Journal 94, 35-41
7 MSD data on file (2018)
8 Leathwick DM, Miller CM (2013) Efficacy of oral, injectable and pour-on formulations of moxidectin against gastrointestinal nematodes in cattle in New Zealand, Veterinary Parasitology 191, 293-300
9 Leathwick DM, Waghorn TS, Miller CM, Candy PM, Oliver AMB (2012), Managing anthelmintic resistance – use of a combination anthelmintic and leaving some lambs untreated to slow the development of resistance to ivermectin, Veterinary Parasitology, 187, 285-294
10 Besier B, Laurenson, Y (2016) Drench resistance management, Paraboss Technical Workshop. Retrieved from www.paraboss.com.au
11 Bartram DJ, Leathwick DM, Taylor MA, Geurden T, Maeder SJ, (2012) The role of combination anthelmintic formulations in the sustainable control of sheep nematodes, Veterinary Parasitology 186, 151-158
12 Whale A, Rendell D (2017) Summary of worm egg count trials conducted by Livestock Logic for Coopers MSD from 2014-2017, Livestock Logic, Hamilton, Victoria
Sources: Boehringer Ingelheim, Coopers Animal Health