The most effective measure against worm infection is to keep the pasture manure-free. This involves looking at the number of animals per hectare. Less than 1 horse or 2 Shetlanders per hectare do not cause very many worms and can be considered relatively 'safe'. When there are more horses on the pasture. pasture management should definitely be applied in order not to increase the number of worm larvae transmitting infections too far. The main rule for de-fattening pasture is: the more often, the better.
A horse with an average weight of 600 kg produces 24 kg of manure per day. This is 10 tonnes of manure on an annual basis, so twice a week de-fertilising the pasture is the bare minimum. Between November and March, once a week is enough.
For pasture management, it is important to know about the life cycle of worms. Below is a simplified explanation of this cycle.
The 5 steps of the worm cycle
1. Horse ingests worm while grazing.
2. Inside the horse, worms mature and lay their eggs inside.
3. The eggs come out with the manure.
4. The eggs hatch and the larvae crawl out of the dung into the grass.
5. Larvae develop into larvae that transmit infections.
What can be learned from this is that point 1 directly highlights the most important measure, keeping the pasture manure-free. Points 2 and 3 are clear. Explaining point 4: a pasture provides a good environment for eggs to hatch. These hatched worms will end up in the grass of the pasture (point 5). Once the horse eats these worms, the cycle is complete.
For parasites such as tapeworm or liver fluke, point 5 involves an intermediate host. In this case, the infection is passed on by another animal (e.g. a sheep). It is therefore important to disrupt the worm cycle as much as possible. A manure-free meadow is very important here! Keep in mind, however, that this does not eliminate every worm infection in the meadow! Eggs and larvae can survive on pasture for quite a long time. With the right measures, however, worm infections can be kept under control. We will discuss 3 of them below.
Looking at what good pasture management entails, there are obviously better solutions. Very important is that horses cannot reach the manure, so cordon off the manure heap with tape or fencing. 2 to 3 metres from the dung heap is sufficient distance.
The worm eggs and larvae survive for a long time in a dung ball. Therefore, do not simply drag the dung from the pasture to a corner. This way, the dung will contaminate the clean grass of the meadow.
Removing the manure is best done in the same way. From the dunghill in the corner of the meadow to the place where the manure will eventually be stored/processed. When doing so, also make sure that the clean grass does not get infected.
If you choose not to remove the dung balls from the pasture, regular pasture dragging is very important. Worms like a warm and moist environment. Dragging the meadow pulls the dung balls apart, causing them to dry out and cool down.
Drag pasture mainly during dry periods (hot or cold) and avoid dragging wet pasture! Dragging in wet meadows can actually have a negative effect, as it spreads the worms in a moist environment.
This is particularly important in areas where the horse dung. Worms prefer long grass because: warm and moist. Then the long grass is eaten by the horse. This allows the worm to develop further inside the horse.
Short grass contributes to disturbing the worm cycle, for best results it is best to mow weekly. Preferably in dry periods and in combination with pasture dragging.