Tree Fodder

Fodder trees and shrubs have always played a role in feeding livestock. Trees and shrubs are increasingly recognized as important components of animal feeding, especially as suppliers of protein. In difficult environmental conditions, where the available grazing is not sufficient to meet the maintenance requirements of animals for part of the year, the contribution from trees and shrubs is significant. Trees and shrubs are valuable sources of fuelwood, shelter, timber, herbal medicines and food for people, and also help to maintain soil fertility. Livestock may also play an important role in the distribution of tree seeds in their dung. An example of this are many of the Acacia species. The seeds of Acacia tortilis are nutritious and are adapted to distribution by wildlife (and therefore also by livestock).

Agroforestry Importance of Leguminous Plants as Fodder Leucaena Prosopis Anti-nutritive Factors Feeding Tree Fodder to Control Parasitic Worms References and Further Reading   Use of Trees by Livestock: Acacia Calliandra Ficus Gliricidia   Radio Scripts: Trees Provide Fodder for Livestock

Tree fodders contain high levels of crude protein and minerals and many show high levels of digestibility. They are readily accepted by livestock and presumably because of their deep-root systems, they continue to produce well into the dry season. However, antinutritive factors can be a problem in some species (Paterson et al., 1998).

Woody species, including trees, shrubs or undershrubs, are an important component of the potential fodder resources for both livestock and wildlife. The fodder value of their leaves and fruits is often superior to herbaceous plants, particularly in the case of legumes. In arid and semi arid zones, they provide the largest part of the protein supply during the driest months; for example, it is estimated that, in the Sahel, up to 80% of the protein ration is provided by plants of the Capparaceae family during the three driest months of the year (Speedy and Pugliese 1992).

The importance of trees and shrubs in the feeding of animals in the tropics and sub-tropics has long been recognized by livestock owners. In arid areas where the growth of herbaceous plants is limited by lack of moisture, leaves and edible twigs of trees and shrubs can constitute well over 50% of the biomass production of rangeland. At high altitudes, tree foliage may provide over 50% of the feed available to ruminants in the dry season, branches being harvested and carried to the animals. Even in regions of higher rainfall where grass supplies the major proportion of the dry matter eaten by ruminants, tree leaves and fruits can form an important constituent of the diet, particularly for small ruminants.

Interest in the planting of trees as a source of feed for livestock has been encouraged by workers in research and development, but in contrast to the hundreds of indigenous species which are used as fodder, attention has focused on a limited number of introduced species. Thus there are publications reporting the chemical composition of Leucaena leucocephala leaves and suggesting management strategies for utilization of the tree for fodder, but it is more difficult to find information on alternative genera which might be equally, or more, appropriate.

Some trees and shrubs are utilized by in the treatment of animal diseases and disorders. See below under "Feeding Tree Fodder to Control Parasitic Worms".

In some areas farmers use trees and shrubs to preserve livestock products such as milk. Wood from some species of trees or shrubs is, for example, burned and produces smoke that is forced into gourds used to store the milk. This smoke improves the keeping properties, or increases the "shelf life" of milk and imparts desirable flavours to the "clotted" and concentrated product (see in Komwihangilo et al. 1995). These uses can usefully be considered alongside the use of trees and shrubs as fodder, with some species providing multiple uses.

Trees are also very important for shade and shelter - especially in semi-arid areas during the dry season. Trees can be planted specifically to supplement existing trees. These can be arranged either as windbreaks, woodlots or scattered individually, and can improve productivity by protecting livestock, crops and pasture from extremes of weather and climate. The value of providing shade and shelter depends on how important these extremes are in relation to other factors that limit productivity. However, the value of providing shelter should not be overestimated.

There are several ways that shade and shelter influence productivity. These are:

• The protection of plants.
• The protection of livestock.
• The alteration of microclimate.
• Reduction in soil losses, and maintenance of fertility.
  
  

Nitrogen is generally the most limiting element in agricultural production. Deficiency of N reduces productivity of crops and livestock. The potential sources of nitrogen include:

• Nitrogen from mineralization of soil organic matter
• Nitrogen from artificial fertilizers
• Nitrogen from organisms associated with tropical grasses
• Nitrogen from biological nitrogen fixation in leguminous plants

Of these, Nitrogen from soil may often, on its own, be insufficient for plant growth especially in most tropical soils which are low in organic matter. Nitrogen from organisms associated with grasses is a minor source. Nitrogen from fertilizers and Nitrogen fixed by legumes are the largest potential sources. Nitrogen fixed by legumes is the cheapest source. Nitrogen fixed by legumes is transformed into protein and this can be consumed by livestock to meet their protein requirements. The excess is returned to the soil in the form of animal wastes. Legumes can also be used as an organic mulch.

Since few other plant families include species with a nitrogen fixing ability, legumes produce the majority of biologically fixed nitrogen and are important in maintaining the Nitrogen balance.

 

Leucaena foliage and green pods are a valuable food source used as fodder. It can be used in zero grazing cut-and-carry systems or as browse for pastured animals. Leucaena can be fed to ruminants (sheep, goats, cattle) and non-ruminants (poultry, goats, swine, fish). It has generally high palatability, digestibility, and nutritional quality (22-28% protein). The leaves stay green well into the dry season, long after grasses and other sources of forage have turned brown. Foliage or pods may be eaten fresh or processed into dried pellets. When properly managed, for example by coppicing, fodder yield can be high (50 ton/ha/yr). Rapid regrowth after coppicing, and overall high growth rate also make Leucaena a high yielding source of fuelwood. High wood density and heating value make it an excellent source fuel or charcoal. In addition to serving as a source of food for livestock, Leucaena can also be planted as a dense living fence to keep animals from wandering.

For more on Leucaena leucocephala

Mesquite or algarrobo (Prosopis species) are now probably the most common trees in the dry tropics of the world. Many species were widely introduced from their native Americas in the past two centuries, and today, epitomize the problems of, and failures in, promoting new dryland tree crops; a number of which are now invasive weeds.

At least 44 species of Prosopis have been described. Most are native to the Americas ranging from the southwestern United States, through Central America and as far south as Argentina. At least three species, P. glandulosa, P. juliflora and P. ruscifolia, are considered as aggressive woody weeds that can cause major problems in grasslands. Prosopis glandulosa, the mesquite of southern USA, has reduced the livestock carrying capacity of over 30 million hectares of rangeland by competing with grasses for nutrients and water. These species spread rapidly due to their ease of propagation and ability to withstand adverse conditions and heavy grazing. They should never be introduced to new locations (National Academy of Sciences 1979).

Other Prosopis species lack the aggressiveness of these weedy types but retain many of their desirable features. They are very drought tolerant and are adapted to the heat and poor soils of arid and semiarid regions. Most require at least 250 mm annual rainfall but some species have been found in areas receiving less than 100 mm. Prosopis species are generally medium sized shrubs or short bunked, spreading trees. Most have spines and although spineless forms do exist they are generally less vigorous than the spiny types. Flowers are most often arranged in elongated spikes or spherical heads. Leaves are compound, bipinnate and feathery in appearance. Usually found on poor land, Prosopis trees thrive on light sandy or rocky soils. Some species like P. pallida are remarkably salt tolerant and dominate arid, saline coastlines. Prosopis tamarugo is the only tree that survives on the arid salt flats of Chile's northern desert plateau where it produces the only available forage, timber and firewood.

Livestock will eat Prosopis pods. In many species the pods contain a sweet, dry yellow pulp and are the seeds contained in the pods are high in protein (34-39%). The pods can sustain livestock in dry seasons when little other feed is available. However, when pods of some species (P. pallida and P. glandulosa) are fed as an exclusive diet for long periods, livestock, particularly cattle, can become malnourished and show ill-thrift symptoms. Thus, it is preferable that livestock consuming Prosopis pods should also have access to other feeds to balance their diet (Gutteridge and Shelton 1998).

Plants have co-evolved with and are eaten by populations of bacteria, insects, fungi and grazing animals, and have developed a variety of defence mechanisms to assist their survival. Leguminous trees and shrubs often have thorns, fibrous foliage and growth habits which protect the crown of the tree from defoliation. Many plants also produce chemicals which are not directly involved in the process of plant growth - and are therefore called secondary compounds (see Norton, 1998). These are largely designed as deterrents against insect and fungal attack. However, these compounds also affect animals (including humans) and alter the nutritive value of forages. Mycotoxins (fungal metabolites) produced by saprophytic and endophytic fungi are also a potential source of toxins in forages.

The effects of both secondary metabolites and mycotoxins vary with animal species. Non-ruminants (e.g. pigs, poultry and horses) are usually more susceptible to these toxins than ruminants which have the capacity to denature potential toxins in the rumen (see the introduction to the rumen and digestive systems).

Hydrogen cyanide is potentially the most serious anti-nutritional factor in fodder trees. Symptoms of cyanide poisoning are laboured breathing, intense red conjunctiva (whites of the eyes), frothing at the mouth, bloat, convulsions and a staggering gait. Post-mortem examination often reveals a characteristic smell of almonds from the stomach contents. A full stomach tends to buffer the absorption of cyanide in ruminants, possibly due to its reaction with sugars or sulphur compounds to form harmless compounds. Poisoning is more likely to occur during drought or periods of feed scarcity, when hungry animals consume large amounts of a particular feed over a short period of time. Avoid feeding pods that are wet. Physically separate potentially dangerous feeds from water sources. Cold water appears to encourage the release of cyanide. Mix potentially toxic feeds with sulphur or molasses, or feed them in conjunction with licks that contain these substances.

Feedstuffs containing tannins are widely used in developing countries, particularly during dry seasons when more nutritious feeds are in short supply. Due to the nature of tannins, the implications for livestock health and productivity are diverse, ranging from the possibility of direct toxicity to the impairment of nitrogen digestibility. Tannins are also implicated in the control of intestinal worms, and whilst they may reduce the digestion of nitrogen in the feed, controlled feeding of certain fodder rich in tannins - particularly some tree species - can have a beneficial effect (for links to more information see below).

Do not be too quick to decide that a tree species can or cannot be used for fodder based on a report you read or even your own quick test. For example, there are many contradictions in the literature regarding the acceptability of fodder from trees and shrubs. Some possible reasons include:

• Acceptability can change during the year. For example, milk goats consume more gliricidia when foliage is older with mature leaves. As the growing season progresses, the proportion of mature leaves increases and leads to improved consumption by goats.
  
• In some cases it may take several days for animals to accept a new feed, but once accustomed they may consume it readily.
  
• Preference for one feed over another does not mean that they will not eat it when it is the only choice.
  
• Within a single species, differences can exist between varieties, individual trees and even between parts of the same tree. Acceptability can be influenced by climate and soil conditions.
  

Poor nutrition is a major contributing factor to intestinal and other parasitic diseases in livestock. Simply put, the message is - Better Feeding, Better Health. In addition, some of the secondary compounds present plants, particularly some tree species, have a direct positive effect when fed in the correct quantities - in that they help to reduce the burden of intestinal worms and other parasites. The following tools provide more information on the relationships between feeding, nutrition and disease control in a number of different situations.

The importance of trees and shrubs in the feeding of animals in the tropics and sub-tropics has long been recognized by livestock owners. In arid areas where the growth of herbaceous plants is limited by lack of moisture, leaves and edible twigs of trees and shrubs can constitute well over 50% of the biomass production of range-land. At high altitudes, tree foliage may provide over 50% of the feed available to ruminants in the dry season, branches being harvested and carried to the animals. Even in regions of higher rainfall where grass supplies the major proportion of the dry matter eaten by ruminants, tree leaves and fruits can form an important constituent of the diet, particularly for small ruminants.

Interest in the planting of trees as a source of feed for livestock has been encouraged by workers in research and development, but in contrast to the hundreds of indigenous species which are used as fodder, attention has focused on a limited number of introduced species. Thus there are many publications reporting the chemical composition of Leucaena leucocephala leaves and suggesting management strategies for utilization of the tree for fodder, but it is more difficult to find information on alternative genera which might be equally, or more, appropriate.

R7351: Increasing the productivity in smallholder owned goats on Acacia thornveld

R6953: Easing Seasonal Feed Scarcity for Goats in Semi-Arid India through a Process of Participatory Research

Friday, J.B. (2005). Agroforestry opportunities for Timor-Leste, Forage banks and forage gardens. University of Hawaii

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Hines, D.A. and Eckman, K. (1993). Indigenous multipurpose trees of Tanzania: Uses and economic benefits for people. Cultural Survival Canada and Development Services Foundation of Tanzania. Ottawa, Ontario, Canada.