pASTURE MANAGEMENT

Dung removal 

By far the most effective way of reducing larval numbers on your paddocks is via removal of the dung. If you remove the manure (and the worm eggs each pile contains) then there will be far less eggs left on the pasture to hatch into the infective larvae. As temperatures increase so does the hatching and so dung removal should be performed every three days. Obviously, this may not be practical for large farms, so other methods will need to be used to minimise exposure. Pasture vacuums are a very effective solution for manure pick up. 

Resting paddocks 

On bigger farms, mares are often moved from paddocks to the working area to be under lights or to foal down. This means that certain paddocks will be partially rested when the mares are moved, and therefore the shedding of eggs onto these pastures (and the number of infective larvae that could develop) has been reduced. It would be a wise idea to take some manure samples from these mare paddocks to carry out FEC. This will help to gauge which are the ‘dirtier’ paddocks with the higher egg counts. 

Cross-grazing 

As the old saying goes: “Drench the paddock, not the animal.” If the egg counts from a particular paddock are high, it would be better to allow older, less susceptible animals to graze these pastures compared with younger stock, or even rest the paddock completely. Resting paddocks effectively is not a practical option for many properties hence if cattle (steers) are available, then they should be moved into the contaminated paddock to help ‘mop up’ the worm eggs and larvae. Yearlings could also be moved onto these paddocks if the contamination isn’t too high to grow these young animals out. Make sure if you are putting your yearlings onto these pastures that they have been drenched with an effective treatment at least three days prior to moving them. 

Harrowing 

As the temperature and moisture levels should be ideal for eggs to hatch into infective larvae, it could be a good idea to harrow the paddock before putting cattle or other animals onto these pastures. Harrowing, followed by one to two months of hard grazing will effectively reduce the infectivity of a paddock by up to half. Imagine your animals being exposed to 1 million infective larvae in a paddock versus the exposure to only 100,000! Care needs to be taken that harrowing techniques do not simply move infective worm larvae over more of the paddock. 

Using older animals to ‘clean’ paddocks 

Generally, older animals are less susceptible to worm pressure than younger animals as their level of natural immunity is higher. If cattle are not available to cross graze, you can use older animals to do the same. This is known as a ‘leader-follower system’. Using this system, younger animals (that are more susceptible to worms and will shed more eggs) are grazed first in a paddock, and then the older animals are used to graze afterwards to ‘mop up’ all the eggs and infective larvae. This also allows the younger, growing animals to graze the new spring protein-rich pasture. Lastly a good practice is to plan ahead for weaning so the paddock is ready in time, therefore minimising the exposure to these very susceptible young animals. By implementing some of these simple pasture management strategies, you can effectively decrease the numbers of infective worm larvae in your paddock, which in turn will reduce your horse’s parasite burden. This in turn should mean you can extend the interval between worming treatments and therefore minimise the number of drenches administered to your horse.