[jumper123]

How often should I deworm my horses if they are out in a grass field all day everyday?Thanks!

[shakti21]

Well 95% of wormsd are in the ground and you can never hope to get rid of them. However I do it every 4-6 weeks. Especially if you tend to have a colicy horse.

[Ryle]

How often you deworm is going to depend on the weather conditions, the parasite load already in your pasture (say were there horses kept there previously that weren't dewormed or are there horses on the pasture right now that don't get dewormed?), the age of your horses, etc.

The most common recommendation for adult horses on pasture is to deworm every 4-6 weeks, however that doesn't take into account the amount of time it takes for your horse to start having adult/egg producing parasites in your horses based on the drug you used and so you can actually end up deworming when you don't need to and missing the time when your horse is actually passing eggs and recontaminating your pastures. Each drug used for deworming has a different egg reappearance peroid and it's best if you intend to just deworm routinely if you use this as a guide for when to deworm again. For strongid or fenbendazole you need to retreat in 4 weeks, for ivermectin it's 8 weeks and for moxidectin it's 12 weeks. If you wait too long, say a full 6-8 weeks after using strongid, then you have more parasite eggs being deposited on your pastures. Deworming this way for a year can really reduce the parasite load in your pastures and make it possible to go to just deworming based upon fecal sample results.

You should also take into account that there are certain seasons where parasite loads on pastures will be reduced---for example the summer in the far south in the USA because the hot dry conditions kill parasite larva which means that your horse will not be getting reinfected as quickly or as heavily. For areas where the winter is very cold and harsh, you may not have to deworm over the winter because your horse won't be picking up parasites like they do during the summer months, so deworming after the onset of severe cold weather and then starting back to deworming when the thaw begins may be ok.

Another method is to have regular fecal egg counts done on your horses to determine when your parasite load is getting high and deworm accordingly. This will mean fewer dewormings in the long run and that means slower development of parasite resistance because the parasites aren't exposed to the dewormers as often. However, with this method you will continue to have pasture contamination especially if you go too long in between fecal egg counts.

A good way to help reduce the parasite burden on your pasture no matter what your deworming program is to pick up feces and dispose of it every 2-3 days so that fewer larva make it back into your pasture.

[Madick]

Originally Posted by shakti21

Well 95% of wormsd are in the ground and you can never hope to get rid of them. However I do it every 4-6 weeks. Especially if you tend to have a colicy horse.

It is actually quite easy to get rid of them if you take control with regular FECs and strategic deworming.

[jiggyboy365]

keep them on a regular routine, i always deworm every 6 weeks