Goats are the dominant small ruminants and rearing them is an
integral part of many farming systems in Laos for many years. It is
a resource that contributes protein and fat to the human diet and
often this enterprise can help farmers to overcome an unforeseen
crisis, which demands immediate finance. Domestic goats in Laos
generally are kept in herds that wander on hills or other grazing
areas. However, the extensive grazing system which is dependent on
the availability of natural feed resources can not provide
sufficient feed during the dry season (Xaypha, 2005). It has been
proposed that one way to counter these adverse effects is by making
available the leaves from trees and shrubs (Steele,
1996).
There are many trees, herbs and shrubs in Laos that have potential as a source of high quality feed for goats but for many of these resources, there is little information about them and they are not well utilized (Kongmanila, 2007). More research is needed to assess the opportunities offered by trees and shrubs and the constraints to their utilization. One such shrub, that grows wild in the upland regions of Laos, and about which little is known, is Tithoniadiversifolia.
The aim of this thesis was to identify the nutritional constraints to the use of foliage of Tithonia diversifolia as the basal feed of growing goats. Tithonia diversifolia (Helms) is a perennial shrub that grows naturally in many upland regions in Laos, where it is used primarily as a green manure. It has been reported that the foliage of Tithonia is rich in protein (more than 20% in DM) and is highly digestible but that the protein in the leaves is rapidly degraded in the rumen to the extent of 85% in 24 hours (Mahecha and Rosales, 2005). Practical observations in Colombia (Rodríguez Lylian, personal communication) indicated that it could serve as the complete diet of growing goats but that the growth rates were very low.
On the basis of these observations it was hypothesised that the
probable constraint to achieving the true nutritive potential of
Tithonia for ruminants was an inadequate supply of metabolizable
protein.
It was proposed that two ways to improve goat performance on
Tithonia foliage as the main feed would be: to feed easily
fermentable carbohydrate, to utilize better the soluble protein in
the rumen and to supplement with foliages with known rumen bypass
characteristics.
Three experiments were carried out using growing goats housed in
metabolism cages so as to study feed intake, apparent digestibility
and N retention with different combinations of Tithonia foliage,
cassava root chips and tree foliages. In Experiment 1, the basal
diet was sun-dried Tithonia foliage and the supplements were
cassava root chips and mulberry leaves. In Experiment 2, a
comparison was made of sun-dried Tithonia foliage and the fresh
foliage with and without cassava chips plus mulberry leaves. In
Experiment 3: the basal diet was fresh Tithonia foliage and four
different sources of leaves (from banana, Erythrina
variegata, mulberry and Jackfruit).