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Animal Health Notebook
Wormy cow Alan Newport
Dewormers may be losing their effectiveness, but they have also encouraged us to stop selecting for cattle that don't need them.

Deworming ain't what it used to be

Good parasite control these days requires us to listen, think and execute using the natural model.

Maybe 10 years ago I was attending a conference at a university vet college.  The noontime meal was above average and I was sitting next to some staff members that introduced themselves as part of the parasitology department.  They did not seem particularly interested in “worm” topics, but I did inquire as to any new deworming compounds that might be showing up in the next several years.  The answer received was that there was nothing new in the pipeline. 

Truth is that we have not had any new classes of dewormers that I am aware since the early 1980’s.  I agree with Dr. Navarre from LSU that small ruminants have been a picture of dewormer resistance for better than 20 years.  I will add that they have also been an example of our leaving the natural model. 

For example, remember that goats have the highest nutrient requirements of all the domestic ruminants.  They are not programmed to consume lots of grass and be healthy.  This is especially true in areas that receive annual moisture of 25 or more inches.  Goats require lots of new growth from brush and trees and forbs.  They can often eat themselves out of a job and health quickly in a high-moisture environment.  Internal parasites, specifically ostertagia, haemonchus and coccidia can take them out in short order.  The same is true for urinary calculi from or as a result of grain feeding.  A bunch of what we have learned about cattle parasitism has been the result of what goats have taught us.  They are the “canary in the coal mine.” 

The major parasite issues in cattle are mostly management or mismanagement decisions.  Remember the following facts:

  • We do not have any new dewormers.
  • There are two negative worms.  The ones killed by the dewormer are the worms that are resistant to the wormer.  If we kill the sensitive worms then the resistant worms have free range.
  • A few hundred worms are needed by the healthy animal(s) to stimulate the immune system.
  • Immune systems are closely tied to nutrition.  Nutrition is closely tied to mineralization, soil health and plant diversity.
  • Time reduces the infective nature of a pasture.  The thumb rule is 70 days but this is likely a minimum, not a hard fast rule.
  • There are lots of plant compounds that are anti-parasitical.  This is significant if they are present in good numbers and the cattle consume good amounts.  Most are considered brush or weeds, such as blackberry briars, willow, buck brush, dock and high-tannin plants).  Cattle are quite easily taught to graze many of these plants.  Some are toxic and we need to beware and pay attention.
  • We cannot deworm ourselves or our cattle out of a worm or parasite problem.  Those days are mostly over. 

I have actually spent many years recommending programs that did not work for any length of time.  I know some good people that do not agree but chances are that they will come around with time.  If it weren’t for money and town jobs they would come around a lot quicker.

Here are some of the natural principles we need to strive to reproduce:

  1. Run the cattle in high densities and graze forage that has been completely recovered, meaning more than 10 weeks.  Use the sale barn and prostaglandins to manage your calving season.  We can develop heifers and bulls in the herd much cheaper and more efficiently than with separation.  Running a single herd takes out lots of costs and allows for lots of pasture growth and recovery.
  2. Cull the animals you deworm.  We cut the switch from their tail for identification.
  3. Wormy cattle often respond to a two- or three-dewormer cocktail in three to five days.  Remember that wormy cattle do not fill up.  Also remember to cut their switch and put them on a non-return trip to town after the drug withdrawal time has expired.
  4. Calves running under a single strand hot wire onto recovered pasture almost never get wormy.  They are or should be acclimated to eat a highly diverse number of plants and stay away from dung.
  5. Do not drag pastures; you are spreading parasites.

Anthelmintics have been a real asset to the cattle business since 1960 when thiabendazole came on the market.  But that sweet spot in time is over.  Now it is time to adopt the natural model principles.

TAGS: Beef Genetics
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