Pre-weaning Drenching - what does the science say?

We often get asked whether it's worthwhile drenching lambs pre-weaning?  Survey work showed that up to 90% of farmers routinely drench their lambs at this point, targeting perceived benefits of better growth rates, less dags, and less pasture contamination.  Unfortunately any increase in drenching also carries an increased risk of selection pressure for resistance.  It is therefore good to have some clear evidence of the benefits of such strategies so that the pro's and con's can be weighed up.

In 2010, to answer this question, Beef+Lamb NZ funded a trial looking at the effects of a pre-weaning drench (normal roundworm), with or without a tapeworm drench (+ Praziquantel).  Both of these were compared to a control group that received no drench.  The tapeworm question was an interesting addition - it had long been thought that tapeworm didn't adversely affect growth.  However some more recent studies had challenged the theory that tapeworms are benign, and farmers also routinely report that they believe tapeworm causes a smelly scour that is attractive to strike flies.

Key Findings:

Weaning Weight

  • Lambs given a roundworm drench were ~0.5kg heavier at weaning than the control group
  • Lambs given roundworm + tape drench were ~1kg heavier at weaning than the control group
  • Lambs given the additional tape drench showed a 24g/d liveweight gain advantage over a straight roundworm drench

Dag Scores

  • There was a dag reduction response to a roundworm drench.  This response was slightly better when a tapeworm drench (praziquantel) was included.

Overall, these figures did support the feeling of farmers that a pre-weaning drench will lead to heavier and cleaner lambs at weaning.  The addition of a tape drench at this point may be beneficial.  Most of our clients opting for a Tape option would use "First" Drench (BZ, Levamisole + Praziquantel).  As with all drenching questions, any gains should be weighed up against the increased risk of resistance.  Our vets can help you examine these pro's and con's for your farming system, so make use of them!