Factsheets - Sheep & Beef
The following fact sheets have been prepared by Anexa FVC Veterinarians as a guide to topics of interest. For specific information please contact your local vet.

Targeted selective treatments

Targeted selective treatments
By Lucy Scott, Veterinarian, Anexa Vets, Raglan

We are selectively treating our dairy cows with Dry Cow, why don’t we selectively drench our youngstock? Wouldn’t this reduce the use of chemicals in our animals and maintain refugia?

Targeted selective treatments (TST) are systems that drench part mobs instead of complete mobs based on liveweight, body condition score, liveweight gain, faecal egg count etc. depending on farming system.

The advantages include that of providing Refugia and being seen to be using chemicals responsibly in our food producing animals. However, the best, most appropriate options are undecided as they all come with some loss of production. In young cattle, at a 72% decrease in drench use, an average 5% decrease in liveweight gain is seen, and at a 47% decrease in drench use, an average 2% decrease in liveweight is seen; not large!

Liveweight gain (LWG) seems to be the most accurate and practical way to decide if an animal requires drench. If weighing regularly, this is something easily implemented. If an animal isn’t gaining the expected weight per day, then they are drenched. Using LWG is effective, relevant, low cost and is mostly practical (although it requires good yarding systems, scales and can increase labour time).

If you don’t know what the expected daily gain for your animals should be, using ‘sentinel animals’ is a good idea. These are animals drenched 28 daily and are used to set the supposed ‘correct’ LWG for a mob. If an animal gains less than 80% of the sentinel animals’ gain, then they are drenched.

Key points include:
  • Not all animals need treatment at all times
  • Faecal egg count is poorly correlated with animal performance/live weight gain
  • Body condition score and liveweight in lambs isn’t useful due to the high variability but liveweight gain may be
  • Setting an appropriate live weight gain target can be a challenge, sentinel animals may help
  • There’s still room for improvement in choosing which animals to treat; research to come!
  • The potential benefits of TST extend beyond providing refugia and need to be harnessed
  • All young cattle should be treated in April due to the risk of type 2 ostertagia
  • Since haemonchus (Barbers pole) has less of an effect on appetite and therefore LWG, we will see clinical signs in lambs before a change in LWG. In Haemonchus areas Lambs should be treated routinely.
The potential benefits and disadvantages of TST depends on many factors but due to the refugia benefits and decreased use of chemicals (cost!) this may be something you can use on farm. Contact your local Anexa Vet to discuss if this is something you may benefit from.


Date Added: Tuesday, 5th March 2019


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