~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Second FAO Electronic Conference on Tropical Feeds Livestock Feed Resources within Integrated Farming Systems ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Abstract of twenty fourth paper, from Mauricio Rosales and Margaret Gill. The analysis presented in this paper has highlighted the following questions which may stimulate discussion: Effects on animal performance: - Toxic components: How accurately do we need to know toxic thresholds? - Digestion: Can we estimate synchronisation indices? - By-pass protein: How do we predict the optimum when tannins are present? - Rate of passage through the digestive tract: Does this relate to palatability? - Intake: How do we predict substitution rates of mixtures? - Optimum animal performance: How to take account of farmers' objectives and feed availability? Do you think that the use of PEG and PEG analogues will permit a large development of feeding systems based on fodder trees and shrubs? Do you have figures on dairy goats fed a full diet of tree and shrub foliage? Effects on the farming system as a whole: - Soil fertility: What is the optimum ratio of legumes to non-legumes? - Biomass production: what are the interactions between species both below and above ground? - Multiple uses: what other uses do farmers have for tree products? The need to maintain the diversity of species: - Dangers of pests and diseases: What is optimum mix from an agronomic point of view? - Indigenous vs exotic species: Does too much reliance on exotic species endanger indigenous species? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TREE MIXTURES WITHIN INTEGRATED FARMING SYSTEMS Mauricio Rosales (1) and Margaret Gill (2) (1) CIPAV - COLCIENCIAS, Colombia E-mail: cipav@cali.cetcol.net.co (2) Natural Resources Institute, UK E-mail: Margaret.Gill@nri.org ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ABSTRACT Fodder trees have always played a significant role in feeding domestic animals. However, scientists have generally undervalued these feed resources mainly because of insufficient knowledge about their potential and the lack of initiative to develop appropriate feeding systems for their use. The conventional approach to the introduction of fodder trees into livestock systems is to exploit "single" species. The reality is that, in many parts of the tropical world, animals eat or are fed with "mixtures" of tree leaves. Cafeteria trials have been widely used to determine relative palatability differences within different plant species. Apart from showing the animal's preferences for a particular fodder species, they also show that, given the opportunity, ruminants will feed on mixtures of forages. Mixed foliage can be given as a supplement to rice straw and others crop residues or may constitute the whole ration. In Nepal and Indonesia, farmers traditionally feed a mixture of fodder tree leaves to their animals. This practice has been observed throughout developing countries, especially with small ruminants. There is negligible published information about the reasons why farmers feed mixtures and the choice of appropriate mixtures currently relies on the farmers' traditional knowledge. The great diversity of plant species used in Nepal may be explained by the improved nutritive value of a combination of species compared to single species on their own, with the underlying reasons being reduced toxic effects and increased variety and palatability of the diet. The use of mixtures ensures a more diverse supply of forages and therefore reduces the risk of dependence on a single plant species. While the use of mixtures of species thus appears to be desirable, there is little scientific information on which to base practical recommendations. Recent results quantified the associative effects in vitro of mixtures of different species of Colombian fodder trees, identifying significant interactions. These suggest that there is considerable potential to develop feeding systems based on strategic mixtures that result in added nutritive value. This can be achieved by capitalising on the interactive processes, such as: protecting dietary protein with natural tannins in order to increase the amount of nitrogen which by-passes the rumen; diluting the effects of deleterious compounds; inducing associative effects that result in an increased voluntary intake; and inducing associative effects on digestibility between the components of the mixture. Appropriate mixtures of tree foliage can result in overall improvement in nutritive value and contribute to making more efficient use of the natural diversity of trees and shrubs in the tropics, and hence helping to sustain it. This paper reviews the literature on the subject and presents the main conclusions from the recent in vitro work. KEY WORDS: fodder tree, shrub, foliage, mixture, forage, feed, toxicity, palatability, associative effect, interaction, tannin, by-pass protein ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ FAO ELECTRONIC CONFERENCE: LIVESTOCK FEED RESOURCES WITHIN INTEGRATED FARMING SYSTEMS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DISCLAIMER: Neither the conference organizers nor FAO accept any legal responsibility for either the contents of this message or any copyright laws that the person sending this electronic message may have violated. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TO COMMENT: Unless you want to reply only to the person sending this information, please send your comments to the address: TFCONF2-L@MAILSERV.FAO.ORG or TFCONF2-ABS-L@MAILSERV.FAO.ORG ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~