Forage Resources

Forage is the major and most important component of ruminant feed. Different ruminants (e.g. goats, sheep, cattle) and non-ruminants (e.g. poultry, pigs) are adapted to use different types of forage. Cattle, for example, are primarily grazers whilst goats are adapted to utilize parts of the tree and shrub forage, or browse.

Use of Forage Grasses Legumes Legume Leaf Meal Tree Fodder References and Further Reading

Forage can be defined as "grasses, herbs and small shrubs that are used as feed by livestock or wildlife". Under natural situations livestock feed on those parts of the available forage resources that they are best adapted to utilize. Many definitions of forage specifically exclude woody plants, whilst others include buds and some types of bark.

Under natural conditions, intake of forages is generally correlated with the amount of nutrients that can be extracted from the different species or types of feed, i.e. its digestibility.

Digestibility is largely determined by features of the plant, including the species, its age or stage of growth, and the season, as well as by the specific physical and physiological characteristics and adaptations of the animal. However, the potential digestibility, and the potential hence nutritional benefit, may not be fully achieved due to interactions between feeds or between one or more feeds and the animal itself.

For more on the different nutritional requirements of ruminants and non-ruminants, go to the section on Nutrition

Ruminants (sheep and goats) and, to a lesser extent non-ruminants (pigs and poultry) are able to use forage (grasses, legumes and tree fodder) as a source of both energy and protein. Forage will also provide some minerals and vitamins, although the amounts and types of the vitamins and minerals provided vary widely between different species of forage. Ruminant animals are able to meet all of their feed requirements from forage provided there is enough available of a sufficiently varied type.

The problem is that forage resources are usually insufficient to meet all of the animals' needs and there will almost certainly be some times of the year when forage supply cannot meet requirements. This is less of an issue with tree fodder compared with grasses and legumes, as the deeper roots of trees mean that they are able to survive and continue to provide green forage longer into the dry season than can grasses, but in most situations, the availability of tree fodder is not sufficient for the number of livestock. Tree fodder may also contain a number of anti-nutritive factors, which reduces its usefulness as a feed. However, as demonstrated by recent research, some components of tree fodder and shrubs may provide compounds that help in combating internal parasitic worms.

Ideally, when forage is cut and carried to livestock, the forage that is harvested will be selected so as to provide a balanced diet that meets all, or most of the animals' needs for different nutrients. This is often difficult or impossible to achieve, since selection is frequently dictated by what is available rather than what may be desirable. However, a number of projects have sought to describe the nutritive value of different forages (particularly tree fodders) so that decisions can be made to strategically supplement particular animals or groups of animals with forages that provide required nutrients.

Types of Forage

Forage can conveniently be divided into three main categories:

• Grasses
• Legumes, and
• Tree Fodder

 

Grasses

Sheep evolved to eat grass, and in the wet season when grass growth is lush, grass can provide all of a sheep’s requirements for protein. In the early wet season, when the grass is growing very fast, it provides more protein than it does energy, and sheep may need to be supplemented with some other source of energy to make sure that they use the protein in grass as efficiently as possible. As the grass matures, particularly after it has seeded, it becomes much drier, with a greater proportion of stem to leaf, and it is then much less valuable as a feed for sheep. Nevertheless, it does make a useful basis of the diet. If grasses can be conserved (by making hay or silage) when it is more nutritious, then it can make a valuable contribution to the diet long into the dry season.

Tropical grasses are generally much more fibrous than grasses that grow in temperate climates, and so are more likely to need supplementing with some form of protein.

Legumes are an excellent source of both protein and energy for small livestock, and have the added advantage of providing nitrogen to the soil in which they are grown. As with grasses, they tend to stop growing in the dry season and they are more difficult to conserve than grasses, particularly as silage as they do not pickle well.

In areas with a long, dry season, most dry fodder will still be capable of providing sufficient energy and fibre for ruminant livestock, but it will become deficient in terms of protein and vitamins. One way to provide the quality fraction of the diet is through the use of dried leaf meal cut from a range of tree legumes. The material is harvested during the dry season, dried in the shade and bagged for use later in the year. When fed at up to 20 per cent of the diet to ruminants, it will improve animal growth rates and milk yields. At levels in the range of 2-5 per cent in the diets of laying hens, it will ensure a rich, yellow-orange in egg yolks.

Tree Fodder

Tree fodders can be utilized as supplements to low quality grasses and conserved fodder.

Goats were evolved to browse, and so are particularly good at utilizing forage taken from trees and shrubs. Tree fodder includes both leaves and young twigs, and indeed both sheep and goats will often eat bark readily. It is not clear whether this is to extract some mineral present in the bark, or whether it is to access more digestible material under the bark. If not controlled, the damage done to individual trees and shrubs by sheep and goats eating bark can be considerable.

Goats can also be used to control the growth of undesirable woody species, and are increasingly used for this purpose in habitat maintenance, restoration and conservation.

In systems that rely heavily on tree fodder for livestock, trees are valued by farmers because of their ability to satisfy hunger and/or promote growth or milk production. Since many trees do continue to produce green forage well into the dry season, they are also valued for this. Different species of tree also recover to different extents after they have been extensively lopped, and this is another factor that will determine how useful a particular species is.

for which proper precautions need to be taken in selecting the species of trees and their level of feeding to grazing animals. Trees often contain a number of secondary compounds, such as saponins and tannins. These antinutritional factors can reduce the value of tree fodder, since although tree fodder may contain a relatively large proportion of protein, this will be of no use to the animal if the tannins in the leaves prevent the animal from digesting the protein. Such trees can be used strategically, however, to some advantage. Depending on the type of tannin that a tree produces, it may be very useful in the control of worms as many tannins have anthelmintic properties (for example, see the tool "Farmers can use Tannins to kill parasitic worms").

CSIRO. World Fertilizer Use Manual: Tropical Grasses. CSIRO, Division of Tropical Crops and Pastures, Queensland, Australia.

Lanting, E., Sevilla, C. and Gabunada, F. (2000). Stylo 184 as a Protein Source in Rice Straw-based Rations for Sheep Pages 149-151 in: in: Stür, W.W., Horne, P.M., Hacker, J.B. and Kerridge, P.C. (eds). Working with Farmers: The Key to Adoption of Forage Technologies. Proceedings of an international workshop held in Cagayan de Oro. Philippines , 12-15 October 1999. ACIAR Proceedings No. 95, 325 pp.