Parasites may be the problem when weight gain is poor

Even seemingly healthy cattle might do better after deworming

Parasites may be the problem when weight gain is poor
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This season has really turned around in Western Canada in terms of moisture.

This has seen the pastures shoot up, humidity run up and should lead to optimal survival of internal parasite larvae. If turnout to pasture occurred at normal times, maximum picking up of larvae has or is occurring so internal levels will be at about their highest.

Every time we check our pastures I know we are on the lookout in case there are sick cattle, hurt bulls, and so on. The signs of higher levels of parasites will often be quite subtle. Clinical signs include coughing and slight diarrhea (if lungworms is the issue) or weight loss.

Keep in mind that those which are most infected are the tip of the iceberg. Rates and degree of infection are such that many are asymptomatic but could still be affected by decreased weight gain.

Of course, initially slight decreases in weight are hard to see but the gaunt, dry haircoat and standing out in a negative way from their cohorts is another clue.

If you are suspicious parasites are increasing, and gains don’t appear to be what they should be, checking into the problem may provide the answers. This year with the flush of grass (and if minerals are being looked after), the growth of cattle should be good. If it isn’t, have your veterinarian check into and rule out internal parasites. Many animals may even have levels whereby they look quite healthy but removing the parasites will have them perform even better once dewormed.

To test the cattle, fresh manure samples are collected and chilled till taken into the veterinary clinic. Fresh means not dried at all and we need a golf ball-sized sample and several from the herd. Older calves and yearling will have the highest levels followed by bulls and cows. Use a zip-lock bag inverted over itself to grasp a small sample.

I have always wondered if the bulls after breeding season that get run down may be good ones to test when they are pulled after breeding. Also keep in mind that each pasture may have different levels of contamination of larvae from the year before.

Your veterinarian will want several samples, but talk to him or her about their protocols for testing. Many of the mixed and large-animal clinics across the West do their own lab tests on counting worm eggs.

A moderate or high count tells us deworming would be of benefit. It also tells us the pasture will have high loads for a few years, so a midsummer deworming will be of benefit. It is called strategic deworming — which is deworming at the appropriate time to benefit both the cattle and help reduce the pasture contamination.

For midsummer deworming, there are several non-handling formulations on the market or others if cattle are going to be processed midsummer. We always need a reason to process but there are many good ones, from treatment for flies to booster shots for calves (or pre-weaning). Pregnancy checking can also be done.

The main products for deworming are the benzimidazoles (such as Safeguard), which is given orally. The first is an oral application with a hook feeder if cattle are run through. It could be with the crumbles or a premix form mixed in the feed. Your veterinarian would have to write a prescription for Safeguard mixed in a mineral mix or another form of fenbendazole which is water soluble. The macrocytic lactone products such as Ivermectin or Eprinomectin need to be poured on or injected. Keep in mind these products are only about 50 per cent effective on internal parasites.

Watch your herd closely for the potential of internal parasites and get them checked if necessary. Some pasture areas or herds may have higher levels than others, so it is not a one-size-fits-all scenario.

Once levels are established, you know the contamination level of the pasture and it will take several years to get the parasite burden down. Make sure your veterinarian is aware of the changing issues regarding internal parasites in Canada. The resistance thing with internal parasites is not new and has been building for over a decade.

About the author


Roy Lewis practised large-animal veterinary medicine for more than 30 years and now works part time as a technical services veterinarian for Merck Animal Health.



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