Deworrners and horse weight- How many pay attention?

[merrygoround]

The title says it all. I know weight tapes are inaccurate but they probably are within 100#. But I’ve observed that several of my horses far exceeded the tapes we commonly use.

But for one reason or another I’ve had them on a real live stock scale, and have learned to judge others from that.

But having seen an owner give a 16.2 big bodied WB a 1100# dose of ivermectin,( Yes, I spoke up), I wonder.

It is understandable as to why resistance to those drugs occurs. You underdose and the survivors develop a tolerance, which they pass on.

[stryder]

exactly right. Or people don’t get it all in. Or the horse spits out some.

[melhorse]

Yes I use a tape and add 200lbs for my worming. With growing horses this is SO important to have the correct dose in the horse at the right time. It is a huge pet peeve of mine that most stables( especially boarding barns) do a tube per horse no matter what :no:

[Kyrabee]

For years, I have dosed Ivermectin as my vet has directed with a deliberate “overdose”. I dose my 1050-1150lb mare with 1 1/4 tubes = 1562 lbs. My friend with a 1600 lb draft cross gives 2 tubes . Ivermectin has a safe profile and allows for this. I would absolutely not do it with moxidectin and I would be darn sure of my horse’s actual weight as in hauling her to the vet an putting her on the scale.

The overage allows for some spit factor and ensures you are dosing adequately. I do not rotate. My horse has been on this regimen for years and has never shown any eggs. I dose my mare for tapes (not very common here) once a year with the 1350lb tube of Equimax only. I do give her the whole tube.

Susan

[saultgirl]

It’s always safer to overdose a little bit on dewormer rather than under-dose.

[Texarkana]

Of course I can’t find the link now, but I think the AAEP recommends you “overdose” by 50kg (about 100lbs).

Any animal I deworm that measures 1000lb and up gets the entire tube-- which is usually labeled for somewhere between 1100lb to 1200lb, depending on the brand. Like everyone else, I do this because of the spit factor and because I’ve found weight tapes to generally read lower than an actual scale. I only dial it down for animals who are measurably under 1000lbs, in which case I use their tape weight + about 100lbs (until they get really small). And obviously, those who tape beyond the weight of the single tube get additional!

With that said, overdosing also leads to resistance. Any survivors are going to pass on their genes for tolerating that slightly higher dose. It’s best to try to be as accurate as possible within a couple hundred pounds.

[Abbie.S]

Resistence to drugs isn’t coming from “overdosing” - it comes from administrating anthelmitics blindly, without knowing what’s it’s your horses gut, what kind of shedder they are and testing a couple times a year to be sure. UNDERDOSING could, over time, lead to resistence, but again, not as much as the aforementioned blind dosing.

My mare hovers around a thousand lbs. I give her the entire tube, usual 1,200 lbs. I do an FEC twice a year, and for the past few years I’ve only had to worm for tapes. Knowledge is power.

[JB]

http://www.cowboyway.com/HowTo/HorseWeight.htm

It’s good to use this, to compare to whatever weight tape you currently have, choose the bigger number, and then add 100lb or so. All my horses, who are between 1200 and a bit under 1400lb, get an 1800lb-ish dose of Equimax, and the bigger one gets a 1500lb dose of Quest Plus, and the others get a 1400lb dose.

[Texarkana]

@Abbie.S;8276024

Resistence to drugs isn’t coming from “overdosing” - it comes from administrating anthelmitics blindly, without knowing what’s it’s your horses gut, what kind of shedder they are and testing a couple times a year to be sure. UNDERDOSING could, over time, lead to resistence, but again, not as much as the aforementioned blind dosing.

Your statement is both true and untrue.

Resistance comes from all of the following: chronically underdosing, incorrect use of anthelmintics (that “blind” use you mention), and overdosing.

Basically, there’s a reason every medication has a dose.

[JB]

Oh, underdosing is absolutely a significant contribute to resistance, just like we have resistance issues with antibiotics because people stop taking them when they feel better, instead of when they run out - that’s the same as underdosing. You could under-dose a Power Pack by not doing all 5 days.

[Texarkana]

[QUOTE=JB;8276621]
Oh, underdosing is absolutely a significant contribute to resistance, just like we have resistance issues with antibiotics because people stop taking them when they feel better, instead of when they run out - that’s the same as underdosing. You could under-dose a Power Pack by not doing all 5 days.[/QUOTE]

Right. But I think where the misconception lies is regarding overdosing not being a contributor to resistance. Resistance to drugs comes from all forms of incorrectly dosing. Overdosing 100-200lbs isn’t particularly significant, especially considering the difficulties of knowing a horse’s exact weight without a scale. But, dosing for say 1800lbs when one has every indication that their horse is only 1000lbs at best does not offer any increased protection, can be potentially harmful for the horse, and can still leave a percentage of highly resistant worms remaining to reproduce.

[JB]

If you’re using a chemical you know is (still) effective, it’s not going to be any more or less effective at the 1800lb dose than at 1100lb. And if it’s not moxidectin, then you can dose many times more than 80% more and still be safe. IIRC ivermectin has been tested safe at something like 10x for a prolonged period, and fenbendazole and pyrantel pamoate even more.

If there’s any thought that any chemical could potentially leave a percentage of highly resistant worms to produce a whole generation of resistant worms, that chemical shouldn’t be used at all, not at the 1000lb dose and not at the 1800lb dose.

[Texarkana]

It’s not a matter of “less” effective, JB. It’s a matter of improper dosing.

100% elimination of parasites is not a realistic goal with today’s anthelmintics. If one is giving a (significantly) higher dose for one’s animal “just to be safe,” that person is exposing those survivors to an increased amount of anthelmintic. Those survivors are going to, well, survive and reproduce. And future generations of those survivors are likely going to be able to tolerate that increased dose. If one is doing this in a closed population over time with other poor parasite management in place, that person is creating a problem for their animals. Especially if they are doing it frequently, as frequency of deworming is probably the BIGGEST contributor to resistance… much bigger than overdosing/underdosing.

[JB]

I’m not trying to be dense, but I’m not getting the logic LOL

I don’t get how extra chemical is going to do harm. If those stronger worms are going to survive more chemical, they’re going to survive the proper dose, and if anything, there’s a chance, however small, those stronger worms would be done in by the increased dose.

The chemical is either going to be a stronger dose for the same time it’s in the body, or it’s going to last in the body a bit longer, and either way, that bodes well for killing the stronger worms. What am I missing?

[Mosey_2003]

I always overdosed ivermectin and fenbendazole. Never Quest, I tried to be within 100lbs when using Quest. But, on my stock horses I had that were both 900lbs or less, they always got the full 1,200lb tube. The pony I deworm for my friend gets 600lbs worth usually. My big guy got a tube and a half (the other half convenient for the pony ;)) I’d rather overdose than under, but I won’t personally give anything smaller than a small horse Quest. It makes me nervous.

[Texarkana]

[QUOTE=JB;8277327]
I’m not trying to be dense, but I’m not getting the logic LOL

I don’t get how extra chemical is going to do harm. If those stronger worms are going to survive more chemical, they’re going to survive the proper dose, and if anything, there’s a chance, however small, those stronger worms would be done in by the increased dose.

The chemical is either going to be a stronger dose for the same time it’s in the body, or it’s going to last in the body a bit longer, and either way, that bodes well for killing the stronger worms. What am I missing?

[/QUOTE]

It’s the same reason we don’t use our “big guns” in medicine every time you need a drug, whether it be anthelmintics, antibiotics, or antimicrobials. Or the same reason the doctor doesn’t tell you to take a double dose of antibiotic to get better more quickly.

Let’s say you give 1.5 times the correct dose every time over years and years (a dose and a half). All of your “survivors” (resistant individuals) are going to always survive 1.5x the dose.

If you have a targeted parasite control program and good rotational grazing practices, it should not be an issue: those worms will get taken out somewhere and never establish a significant population.

But let’s say a farm doesn’t have “perfect” parasite management, like so many of us don’t. Those 1.5x dose tolerant parasites are going to be able to slowly increase their population size over time. You are essentially contributing to the creation of a population of slightly stronger parasites that are not only resistant to the regular dose, but also 1.5x the dose.

[merrygoround]

[QUOTE=JB;8277327]
I’m not trying to be dense, but I’m not getting the logic LOL

I don’t get how extra chemical is going to do harm. If those stronger worms are going to survive more chemical, they’re going to survive the proper dose, and if anything, there’s a chance, however small, those stronger worms would be done in by the increased dose.

The chemical is either going to be a stronger dose for the same time it’s in the body, or it’s going to last in the body a bit longer, and either way, that bodes well for killing the stronger worms. What am I missing?

[/QUOTE]

JB I guess I’m equally dense as you. Texarkana’s logic defies logic.

[merrygoround]

Gee whiz, Merry and JB, got room for me?

[Texarkana]

[QUOTE=merrygoround;8278130]
JB I guess I’m equally dense as you. Texarkana’s logic defies logic.[/QUOTE]

I’ve been very polite in this discussion. Everyone in disagreement has been very polite. Perhaps you should follow suit?

If you don’t get it, you don’t get it. You’re not the only one. Which is part of the reason we have resistance and tolerance issues across the board-- with anthelmintics, antibiotics, antiprotozoals, antifungals… it’s hard to shake the notion that “more” does not always equate to “better for the long term.”

[ReSomething]

Um, I think I get the logic. You are, rightly or wrongly, breeding for survivors, and at 1.5 the dose you have bred for survivors of 1.5 times the dosage.

I’m trying to remember how it is phrased for poisons, something like ppm’s, you have exposed your population to that much higher a level of ppms and they have survived it and are now your breeding population, they are likely to pass on their ability to tolerate those levels to their offspring, and you’ll need to increase the ppm’s in your dosing to account for that. And meanwhile the poor horse hasn’t acquired any kind of increased tolerance.

And yes, I use my weight tape for deworming and for sedation. I worry about the old guy keeling over from an excessively depressed respiratory system sometimes.