Should we be worming our adult dairy cows?

This is a question that we often debate and more often than not the answer is no. If I was to suggest to you that the banks were going to give you a return on your savings of 10:1, I think many would likely jump at those odds.

In a North Island study (Hickman, B – unpub.) of adult cattle going through the abattoir, more than half showed evidence of significant parasite damage to the fourth stomach (abomasum). This data is similar to published data from France which looked at cattle abomasa for a two-year period (2009-2011).

If we consider that this information is showing over half our adult cattle have damage, where is this damage coming from? Our cattle are resistant to worms by the time they are adults; they never show clinical signs of worms; they act as pasture cleaners don’t they for our young stock?

The fact is adult cattle are still subject to damage from the early larval stages before their immune systems have a chance to recognise and kick out the adult worms, usually before they start to produce significant quantities of eggs!

It’s this larval damage to the mucosa of the gut lining that can cause the problems; it incites an increase in gastrin secretion (this is an appetite depressant), and along with the natural immune system’s demand for glucose when responding to these larvae, we see a net loss in energy available to the cow. This net loss is through decreased drive to eat from increased gastrin and therefore reduced intake potential, and the loss of available blood glucose to the immune system, i.e. to non “productive” functions in terms of animal profitability but a vital function no less. Damage to the gut lining will also act to potentially decrease the digestive efficiency of the gut (Gibb et al 2005), i.e. we don’t get out that which we would expect from what is going in!

So how and when can we act on this and how can it be worth up to 10:1 on our investment?

A New Zealand study conducted in 2013 season, looking at the question of effect of treatment, showed a response to treatment of around 0.03kg milk solids (MS) per day over the whole lactation (Lawrence et al 2017). This result agreed with a previous study also showing around 0.03kgMS/d over a 250-day lactation (McPherson et al 2001). This is interesting when you have more than one scientific study showing very similar results!

If we think about what this is worth, then if we work on an industry average of around 274-day lactation and multiply 0.03 x 274 we get an extra 8.22kgMS/cow; at a payout of around $6.45 this equals around $53. If the treatment cost is approx. $5.30 for the product this equates to a 10:1 return. This doesn’t include benefits from improved energy balance and the positive effects this has on first service conception rates etc and future days in milk.

So which drench should I use? The studies above used the active Eprinomectin (Eprinex® or EpriSure®). These pour-on products have a NIL milk and meat with-hold so are safe to use in early lactation and are non-bio-accumulative.

When to drench? Many dairy farmers apply a whole herd pour-on at dry-off, combining lice and internal parasite control using Cattle Pour or Genesis or Reflex, then a month before mating starts treating with Eprinex® or EpriSure®.

Selective drenching can also be used during the season to assist lighter cows and feed conversion efficiency!

Please discuss with your veterinarian the best time to look to drench your adult cattle, it’s a good time now to put plans in place for next season.


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