The dangers of under dosing when worming your horse.
A common mistake when worming horses is under dosing, so ascertain the weight of your horse as accurately as you can either by using a weight tape or even better a weigh bridge. Correct dosing is important, if you under dose your horse the product will not work efficiently and could lead to resistance.
If you administer a sub therapeutic level of the drug and thereby expose the worms to the drug, but perhaps not at a sufficient dosage to kill them, worms that survive treatment may pass on their “immunity” to subsequent generations. Those generations will then become more adept at surviving chemical treatments, with the potential for resistance to develop to that drug.
There are brands on the market that now that treat up to 700kg in a single syringe and now some available in tablet form with each pack treating up to 800kg. These larger syringes and tubes give that little bit extra to play with when dosing. Many popular brands only treat up to 600kg of bodyweight, so you may need to take care when working out the doses required with many horses needing more than one syringe.
When you estimate the weight of your horse remember we all lie about our weight so if in doubt when estimating the weight, err on the generous side. Although a slight overdose of wormer is unlikely to have harmful effects, as with all drugs, it is important to dose accurately and in accordance with the manufacturer’s recommendations.