Drench & Mineral Trial Update

10 Dec 2021

Summer Update - Injecting Some Evidence into Cattle Worm Control and Trace Mineral Use

Nathan Jennings Senior Land Services Officer - Livestock, Lismore.

In our Spring issue we wrote about two trials being run by North Coast Local Land Services and the NSW Department of Primary Industries looking at the effectiveness of injectable trace minerals (Multimin) and injectable drenches for young cattle on the north coast. The following is an update on what those trials have found over the last few months.

Injectable Trace Minerals Trial

Steers in this trial were moved from Wollongbar to the Duck Creek research station so we could investigate the effects of stress and change of diet on weight gain and changes in general health. All steers continued to gain weight at acceptable backgrounding rates whether they had received further booster doses of Multimin or not.

These steers have now received 3 doses of Multimin and, despite being run in the same paddock at the same time as the untreated steers, the addition of Multimin has not shown any weight gain or financial advantage at this point. In early November both groups of steers averaged 431kg each.

All steers are due for a final weigh in on the 8^th of December before leaving the north coast for “Tullimba” research feedlot at Armidale. From here the steers will receive further Multimin treatments and be fed until late March before processing. We will continue to investigate any potential benefits on weight, immunity and carcass quality that could potentially be attributed to Multimin through the feedlotting stage.

Final results are expected mid 2022 - we will keep you updated as we progress.

Injectable drench trial

This trial was run at the Pearces Creek Research station from April 2021 with 280 cross bred weaner steers purchased from across the far north coast. The steers were selected from a much larger initial purchase and assigned groups to ensure an even allocation of properties of origin, weights, worm burdens and freedom from other internal parasites such as liver fluke. We were investigating the effectiveness of six of the most common injectable cattle drenches available on the market at present.

The aim was for a 120-day trial, however on day 63 after treatment we had to intervene and treat the steers. This was due to ongoing weight loss and the inability of any of the injectable drenches to reduce the worm burden sufficiently. Rapid reinfestation by the key worm species was also observed. Low levels of control and high larval pickup from pasture were the most likely cause for the fast rate of reinfestation.

This finding confirmed the results from the Duck Creek research station trial in 2020. It also provided more evidence around the increasing issue of drench resistance in the macrocyclic lactone (ML) family, for example - products containing Ivermectin, Moxidectin, Doramectin, Abamectin etc as the sole active ingredient.

All the injectable drenches provided some degree of worm control and were far better than not drenching at all.

Regardless of administration method (injection, oral, pour on) graziers should be considering the active ingredients in the drenches they use and design programs accordingly. This should include:

Rotating chemical families,
Use of combination or concurrent treatments that include multiple active ingredients for weaner aged cattle, and
any non-chemical worm prevention practices available, such as paddock rotations with adult cattle.

9 key messages for producers from both drench trials which have looked at pour on, oral and injectable drench products:

These results do not suggest there is one single superior product, nor were the trials ever intended to be a competition between products. They do suggest we need to take greater care of what products are used if we want to have effective treatments in the future. Worm resistance on the North Coast is emerging to all ML single active products.
The oral drenches oxfendazole and levamisole still provide good control. If you have been using these repeatedly with minimal to no rotation of chemical families then they may not be as effective as these trials have demonstrated. These products could also become less effective with continued single use and no rotation.
Best results came from the use of a combination of products or concurrent treatments (multiple actives at once), with regular reassessment and change - avoid using the same product or treatments repeatedly.
Worm testing and identification will give a clear indication of what treatments are needed and also enable you to determine how effective, or not, a treatment has been. Assumptions can contribute to increased resistance.
Barbers pole worm and Cooperia are major worms of concern on the north coast. Rapid reinfestation from pasture is likely highlighting the importance of worm control programs long term.
When effective treatments are used, weight gain differences are established early. This can be related to animal value.
Once worms get out of control and pasture contamination is high the effort required to control the infestation is significantly higher. Once achieved, young cattle are likely to express some compensatory growth.
Some natural tolerance to worms does develop and weight loss stops, however untreated animals will experience lower weight gain than animals that have been treated, regardless of what treatment they received.
The impact of worms is higher when there is a period of stress or poor nutrition. Worm control at weaning and other stressful times is important for young cattle.