If you find
Selective grazers often overgraze the good stuff (as they see it) and undergraze other plants
Leaving the least appealing plants to continue growing causes many weed problems in pastures
Sown or improved pastures often don’t last long enough to pay for their establishment
Overgrazing happens one plant at a time
Woody weeds take over many rangelands
Some animals revisit and regraze a plant, almost the moment a new leaf appears
Any animal which is unable to move because of fences, predators etc is likely to overgraze an area
A selective grazer is any animal that is able to aim for and get a particular plant. Selective grazing involves just what it says, selecting something and then grazing it.
The ultimate selective grazer on the farm is probably the sheep because it:
- can PICK UP small seeds with its lips
- can NIBBLE just this leaf and not the one next to it and
- likes to REVISIT the plants it has grazed to get the fresh regrowth.
Horses are also selective, just not as accurate nor as nimble.
Goats are selective browsers and grazers, eating shrubs, trees and pasture plants.
Cattle are less selective because of their greater mouth size, different method of grazing — often they pull off a mouthful of grass and sometimes they pull it right out of the ground.
Hippopotamuses and rhinoceroses (not common on farms) are not very selective because of their vision and mouth shapes. Elephants (again, not common on farms) are very selective because the length and manoeuverability of their trunks gives them the ability to see, smell, select and uproot or break off their chosen fodder.
Selective grazing happens when a selective grazer is allowed to choose what it will graze. This happens a lot when animals are set stocked rather than rotated. They graze the plants in order of their preference. They graze and sometimes overgraze the good stuff (as they see it) and undergraze the rest. This means the least appealing plants are grazed last, if at all.
Leaving the least appealing plants to continue growing causes many weed problems in pastures.
This sort of broad-scale selective grazing also occurs with rotational grazing when the graze and rest periods are out of balance with the farm’s needs. And the result can be the same, an increase in weeds and a decrease in the most palatable and most digestible plants.
Non-selective grazing happens when animals are given no choice in what to graze by the farmer deciding:
- what types of animals and
- how many of those animals will put
- how much grazing pressure
- on how large an area
- for how long.
By making it hard for animals to graze selectively, the farmer takes back control rather than letting the animals decide. If a farmer decides well,
- weed problems decline
- pasture quality improves
- animal performance improves and
- the enterprise becomes more profitable.
However, if management is not up to the mark, problems are likely to increase and the farm environment is likely to go backwards. There are plenty of opportunities in the process for Learning from pests.