Invest in worm control to promote productivity in the dairy herd.

The current problems of low milk prices faced by dairy farmers mean that increasing productivity is even more critical.

Low milk prices mean that maximising the number of litres produced and minimising the cost of production is paramount.

To do that requires ensuring that cows are in the best physical shape, allowing them to deliver in terms of milk yield and solids.

The gut worm threat

Infections with Gutworms are very much an underestimated cause of reduced performance in pastured dairy herds.

Previously it was always assumed that adult dairy cows could easily deal with parasitic infection and that such infections would not have any detrimental effect on productivity.

Recent evidence has emerged regarding the negative impact that gutworms can have on the productive performance of adult dairy cows.

The effects of gutworms in dairy cows can be divided into clinical and subclinical effects. Outward visible symptoms-clinical signs of gutworms including scouring and rough coat are relatively unlikely to occur in adult dairy cows. This is more common in young stock during their first or second grazing season.

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Losses in the animal’s productivity without outward clinical signs, otherwise known as subclinical effects are the much more common presentation in adult dairy cows.

Subclinical infections are more difficult to detect but are a major cause of reduced productivity in dairy herds.

Adult dairy cows can harbour a large number of gastrointestinal parasites (mainly Ostertagia ostertagi).

One 1999 study found that between 83% and 100% of culled dairy cows were infected with gut worms. If as this study suggests, most herds are suffering from a high gut worm burden it means Irish dairy farmers are losing money as a result.

Dairy cows are bred to produce vast quantities of milk and are therefore under nutritional pressure so even a few parasites can reduce production in these high yielders.

For example, the same burden of worms in a suckler cow is likely to cause little or no production losses. Because of the demands of lactation it takes fewer parasites in high producing dairy cows to cause economic losses than it takes in lower producing animals that are not under the same pressures.

Gut worms can also affect the animal’s immune system. Animals harbouring a gutworm infection will be immunosuppressed. This can interfere with the animal’s ability to deal effectively with infections that they are exposed to. The freshly calved, transitional cow is already immunosuppressed and the presence of worms magnifies this immunosuppression.

The benefits of worming dairy cows with an Eprinomectin cased wormer:

1. Milk Yield

Numerous studies have shown that a worming treatment of dairy cows can result in a positive milk yield response. Studies show up to a 2l increase per cow per day.

The quality of the milk produced from treated animals is also superior, with consistently higher milk fat, protein and overall milk solids.

2. Animals graze longer

Treated animals have also been shown to graze for up to an hour longer each day, which can increase their DM intake by up to 1kg per day.

Milk yield is positively correlated to dry matter intake. High dry matter intake (DMI) results in high nutrient intake and therefore higher milk yield, where the difference in yield was up to 2.35kg/day between treated and nontreated, and is particularly marked in heifers.


Not only are there significant benefits to worming treatments in terms of the production parameters, the fertility indices of treated animals can also be significantly improved, with improved calving to conception intervals associated with treatment at calving13, and higher conception rates at first service (58% treated animals V 38% nontreated).


A bulk tank milk test for the measurement of antibodies to the main gutworm -Ostertagia ostertagi exists. This test helps to give an indication of the level of exposure within a herd to this harmful gutworm

The results of this test are expressed as a ratio and offer an excellent tool to assess parasitic burden within a dairy herd.

The higher the ratio the greater the potential benefit of treatment of that herd for gutworms. Overall the Bulk Tank Milk Tests can be used to identify those herds where the greatest milk yield response after a worming treatment is expected and can contribute to a strategic and justified use of an anthelmintic.

Lungworm in Dairy Cows

Over the last number of years the problem of coughing dairy cows has become much more prevalent. Reinfection Hoose or lungworm can be the cause of this.

When the immunity of these adult animals is low, they can become parasitised by lungworm larvae, resulting in the clinical signs of coughing, milk drop, weight loss and secondary bacterial infections.

If adult cows that are only partly immune to lungworms are exposed to heavy larval challenges from pasture they may develop severe respiratory signs.

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Pasture grazed by calves will be likely to have a heavy larval burden. In situations, where wet weather follows a period of dry conditions this can cause a mass release of lungworm larvae from dung pats increasing the likelihood of animals developing lungworm.


Clinical signs of lungworm include coughing and difficulty breathing, as well as milk drop, weight loss and death in severe cases. Famers should remain vigilant of these clinical signs and take steps to treat appropriately.


As soon as lungworm is identified in a herd, it is extremely important to treat the whole herd and to instigate treatment as quickly as possible.

Delaying treatment can result in permanent damage to the lungs, affecting the animal’s long term performance as well as making them more susceptible to secondary infections.

Treating cows with lungworm is quite different to treating cows with an underlying gut worm burden. Cows with lungworm are clinically sick while, those with gutworms are more likely to be clinically well but production may be compromised.


Eprizero 5mg/ml Pour On Solution for Beef and Dairy Cattle is a convenient and effective pour on solution for the treatment of gutworms, lungworms and external parasites. It offers a zero milk withdrawal period making it the ideal choice for dairy farmers as it can be used strategically at any stage of lactation. It also has an improved meat withdrawal period of just 10 days. It is fully rain fast and its unique formulation means shorter time to effective blood levels.