Stomach worm infestations are on the rise in dairy cattle this year, according to a Kilkenny-based veterinary surgeon.

Richard Brennan, of the Thomastown Veterinary Clinic, said other worm infestations – such as lungworms – are also becoming more common.

“Older stock are becoming increasingly susceptible to worm infections,” he said.

Brennan said that stomach and bowl worms will start to become a problem from mid-to-late June.

“The incidences of lungworm infection in dairy cows and replacements have increased in recent years. Cattle just can’t build up immunity anymore.

“The animal isn’t getting challenged by a worm infection in it’s first grazing season anymore, due to the effectiveness of the doses and vaccines.

“Immunity can be boosted through vaccines,” Brennan said.

Animals are so well protected nowadays, in their first season of grazing, that it’s possible the animal will pick up its first lungworm infection during its second grazing season.

This protection will occur from dosing at regular intervals, throughout the animals’ first grazing season.

Breeding heifers in particular, should be watched and treated for lungworm accordingly. They are at risk as they are second-season grazers.

Symptoms of lungworms, stomach and bowl worms can include: a drop in milk yield; a deep, husky cough; a reduction in average daily gain (ADG); and a loss of condition, he said.

“Moisture and heat are required for worm populations to thrive,” Brennan added.

Brennan mentioned that dung sampling is a very effective way of determining infection.

If the Faecal Egg Count (FEC) is 300-400 eggs per gram of dung, he said, a dosing and/or vaccinating programme should be developed and implemented immediately.

How to fight worm infections

Anthelmintics are the most commonly-used drug to control worm infections. White drenches are effective, he said, and products such as Valbazen are very commonly used.

However, Brennan did say there are now concerns regarding resistance to white drenches.

Ivermectin is another chemical which is capable of controlling worms.

“Sometimes when these products are used they can actually make the animal worse for a few weeks – especially in cases of heavy infestations.

“If you suddenly kill all of these parasites at once, there are a large number of dead and rotting worms within the animal’s body.

If the dead worms are in the lungs, for example, the animal will actually cough harder to try and remove these rotting worms from its lungs. This can put the animal under pressure for a few weeks.

Natural control

First-season grazers (calves) should get priority to the freshest and most-palatable grass. Calves shouldn’t be made graze low to the ground, as this is where the worms lie within the pasture.

Calves should be moved from paddock to paddock regularly, he said, and older stock should be used to clean out the paddocks after them.

The older stock can tolerate these worm burdens, as they have some immunity. This type of grazing is known as leader-follower grazing, he said.