How to control farm parasites

WHILE ground conditions and grass supply are still very good in most parts of the country, from now on, as we move further into the autumn period, we will see more animals being housed on farms.

Whether it is weanlings, store cattle or cows and calves, controlling parasites in all classes of stock at housing is extremely important. It ensures that animals keep thriving during the winter period and that we get the maximum return from the feed that they are consuming.

Housing marks an abrupt transition for animals from pasture-based husbandry to their management indoors, and this has implications for parasites and their control. Cattle pick up infections with worms and liver fluke almost exclusively while grazing at pasture, because the infective stages are located on the pastures and survive poorly on conserved forage.

Thus, when cattle are housed, they no longer pick up new worm and liver-fluke infections until they are turned out onto grass the following spring.

This means that effective parasite control at or during housing should keep the animals virtually free of worms and liver fluke until they return to pasture the next year.

So, how well is your herd performing? Before considering the parasites themselves and what parasites you are going to treat the animals for, it is worthwhile to consider the performance of the stock over the previous grazing season and how they have performed up until housing.

Indicators including growth rates and weights; milk yield; condition score and fertility rates should all be monitored and used as signs of an underlying parasite issue within the herd.

The number of parasites carried by cattle at housing can vary according to several factors. These include their age, as older animals generally become more resistant to some parasites; their health status; stocking rates; previous grazing management and the level of previous parasite treatments.

As should be the case with all parasite control treatments, it is advisable that you consult with your vet in order to determine what level of dosing is required.

For example, one should consider what they are dosing for; what products they should use and at what intervals animals should be treated.

Some useful tips that you could consider might include the following:

Combination products should be used appropriately for the target parasite species.

Pay particular attention to dose-to-weight calculations to ensure animals receive a full dose as it is important that you are accurate with your weights. If possible weight a sample of animals in the group.

Consider what products are suitable for you in terms of labour availability and handling facilities, and whether you will use a drench, injection or pour-on.

Read the label and instructions for the chosen products carefully to ensure that you know exactly what they can and cannot do, and set your targets and expectations accordingly.

For worms, it is best to use products that are active against both adult and inhibited larvae of the stomach worm.

Whilst acceptable levels of liver-fluke control can be achieved with a treatment at housing time, if infection levels are high and, particularly if animals have picked up a lot of new infections just before they are housed, then a more stringent approach may be required.

Although we have experienced a very dry summer, this does not rule out the possibility of cattle having liver fluke.

Depending on what product you use for fluke treatment at housing time and the stage of infection that is controlled by the product, it may be necessary to treat the animals twice: once at housing; and another treatment six to eight weeks later.