News & Advice

Will worm drenching your milking herd make you money?

Aug 1, 2018 | Dairy, Dairy Animal Health & Welfare, Milk Quality

A study by Massey University published last year has confirmed previous research; that a treatment of EPRINEX on adult dairy cattle does increase milk solid production. The study showed that on average, a herd treated with EPRINEX would expect an increase in production of 0.03kgMS/cow/day for the remainder of lactation. There have now been two large independent studies looking at the effect of EPRINEX on milk yield in New Zealand and they both had similar results (+0.03kgMS/cow/day on average). Note that this research and resultant increase in milk-solids production has been shown only in EPRINEX in New Zealand.

For the average herd the treatment is cost effective. Treatment on average costs $5-6 a cow and in early lactation, based on a 0.03kgMS response for 250 days (7.5kgMS) at a $6 payout, that’s a return of $45.


So, is your herd going to get this average response? 

There is no simple or single answer to this, and there are still some parts of the science we don’t have answers for yet, but to make an informed decision about drenching your herd we would like you to consider the following factors that may influence the response (some of which may be intuitive but some you will need to have a chat to your Vet about);

  • What is your stocking rate? 
  • What is your herd BW? 
  • What are your pasture residuals on average for the year? 
  • Do you have a healthy herd or are there other conditions affecting immunity such as Johnes Disease, BVD or a history of Facial Eczema? 
  • Are your cows under feed or climatic stress at this time? 
  • Do the youngstock (calves or heifers) graze on the milking platform? 
  • Are the cows grazed off farm for any length of time where youngstock graze? 
  • Do you quarantine drench stock when they arrive back on the milking platform? 


If you have then decided on a worm treatment for the adult cows, there are still more factors to consider: 

  • When using a pour-on application, which for practical reasons, is most common in adult animals, to be effective it needs to be applied in fine conditions, we would say at least 2 hours without rain post application.
  • Is this the right active ingredient? 
  • Certainly EPRINEX (Eprinomectin active ingredient) is the only product proven to give a milk production response in New Zealand, but if your herd has a history of liver fluke infestation then this active will not treat the fluke 
  • Have you used this active ingredient in your calves and suspected (or measured with testing) it hasn’t worked as well as it should i.e. is there some resistance appearing in your worm population? 


What time of year will you treat the herd? 

  • Historically there has been evidence to support treating around calving or in early lactation, but the recent research from Massey was done in the summer. The benefits in later lactation are likely associated with improved dry matter intakes and reduce energy for immune challenge from the worm larvae, therefore there is more energy available for BCS gain or growth in late lactation early dry off. 
  • If you have quarantine drenched you R2s on arrival home from grazing, there is no point treating them again in early lactation.

We strongly recommend you consider your options and talk to your vet about what’s best in your herd, which is likely different to what your neighbour does! 


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