Parasitic Infections In Adult Dairy Cattle

Adult dairy cows can harbour a large number of gastrointestinal parasites

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A large scale abattoir survey carried out in the Netherlands, UK, Germany, Belgium and the USA found that 83-100% of culled dairy cows were infected with gutworms but what does this mean in terms of a cow’s performance?

Milk Production & Quality

Numerous studies have shown that strategic anthelmintic treatment with Eprinomectin (e.g. Eprizero) can result in a positive milk yield response, varying from 0.35 to 2 litres per cow, per day; this effect is particularly marked in heifers.

The quality of the milk produced from treated animals is also superior, with consistently higher milk fat, protein and overall milk solids. Eprinomectin-treated animals have been shown to graze for up to an hour longer each day, which can increase their dry matter intake (DMI) by up to 1kg per day.

Given milk yield is positively correlated to DMI; high DMI results in higher nutrient intake and, therefore, higher milk yield.


Not only are there significant benefits to eprinomectin treatments on production parameters, the fertility of animals treated with eprinomectin can also be significantly improved. Improved calving to conception intervals and higher conception rates at first service are associated with treatment at calving.

The elimination of parasites around calving time is thought to improve energy balance during the post-partum period, thus reducing metabolic disorders, with consequent significant benefits on
reproductive performance.

In conclusion, strategic use of eprinomectin e.g. first lactation heifers at calving or any cows with low BCS (Body Condition Score) at housing, can have a positive effect on yield and fertility.

The COWS Five Rs Principles

Wormers should always be administered following the COWS five Rs principles:

  1. RIGHT product
  2. RIGHT animal
  3. RIGHT time
  4. RIGHT dose
  5. Given in the RIGHT way

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