To digest is to break down food in the rumen and/or stomach plus intestines etc into substances that can be absorbed and used by the animal.

So digestibility refers to the degree to which something can be broken down, absorbed and used.

If 70% of the material can be used, it is said to be 70% digestible. In very rough terms, this means that 30% will pass out in the manure. So if the animal eats 10 kg and passes 3 kg out this is roughly 70% digestibility.

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Of course it only works like that if you can get a dry matter measure in and a dry matter measure out, plus if you know which bits were eaten when and so on. But it is a handy rule of thumb.

Often the limit on any animal's production is the amount of nutrient it can get. The more an animal eats and the less it passes out the better, because it is being used by the animal for growth, movement, production etc.

This obviously will not work if the feed is passing so slowly because it is indigestible. Then it would limit what the animal could eat because the previous material was not being used up. So the animal would have to wait until the previous material had passed out the rear end before there was enough room for more feed in the system.

Giving animals higher digestibility feed allows you to maximize production because the animal can eat more. This is because it doesn't linger in the rumen but is passed out of there fairly quickly so that it can be absorbed in the later parts of the digestive system. Also, more of it gets put straight into use and there is less waste.

Digestibility of pasture and standing forage
Digestibility percentage What this digestibility percentage means and what such feed is like As any part of the plant at this level of digestibility ages, it does this
75% and higher This is the quality of good new growth It is most likely growing rapidly
65% This is green material, but declining in quality as the plant converts it steadily into structures to support more new growth Becomes tougher, less nutritious, less juicy
55% The material will be green but losing more quality still. It may well be senescing.
In the case of plant leaves this is worse than just growing old, it's beginning to fall off the twig, something humans save till the end
Becomes tougher still and thus
MORE able to support the plant with rigidity but unfortunately

LESS able to support your growing animals profitably
45% This is well into the degradation stage. Some parts of some plants will be detaching because they are no longer of use to the plant Leaves may be dropping and becoming
LESS a part of the plant and

MORE a part of the landscape through turning into Litter
35% Very little material of this degree of digestibility will remain on any but the woodiest plants where it has become the structure of the plant Detaching and falling into the litter layer

We try to make our pages as digestible as possible so you don't have to process too much fibre. This way you can absorb more and make more use of it.

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This page was updated on December 27, 2007