WHILE research is indicating drench resistance in beef cattle is not having an effect on weight gain at this point, animal scientists believe we are very close to the turning point.
A study involving six southern NSW beef properties showed anthelmintic resistance (AR) was widespread but was not impacting production in the majority of cases.
But the use of a combination drench will likely be prudent in the future, according to Professor Bruce Allworth, from Charles Sturt University’s School of Animal and Veterinary Sciences.
“What I think is happening is we are removing enough worms that we haven’t had a significant challenge to worry about weight gain yet,” he said.
“But if we continue to use the single active and get a crook season we will see a big weight difference.”
Prof Allworth led the research last year, which compared the effectiveness of a single active mectin drench with the combination pour-on products both in terms of efficacy and weight gain.
Two treatment groups of around 50 steers were given single active and combination treatments, plus a group of control animals was monitored.
Prof Allworth explained AR was well-recognised in sheep flocks but due to both less precision in egg counting techniques and generally low egg counts in beef there had been limited work around drench resistance in cattle.
“The gurus believe that combining actives is a more effective way of minimising resistance than rotation or using single actives,” he told delegates at the Animal Production conference held in Wagga Wagga last week.
“What we were interested in was the production advantage in using a combo drench versus a single active.”
Resistance was detected to the single active on five of the six properties, while the abamectin/levamisole combination drench was considered effective.
Animals treated with the combination were significantly heavier at three, seven and 11 weeks on just two farms with the majority showing no significant difference despite AR being present.
Cooperia was predominant worm.
Prof Allworth said the results indicated resistance was likely present in many southern beef herds.
“The six herds were not selected on the basis of any suspicion of AR but rather because they were competent operators,” he said.
“Given the likelihood of resistance, it would appear prudent for cattle producers to consider using combination drenches even if weight gain advantages were not always apparent.”
The continued use of a single active is likely to lead to even greater resistance, making anthelmintic failure, weight loss and clinical parasitism more likely, he believes.
The story Drench resistance widespread in southern beef herds first appeared on Farm Online.