~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Second FAO Electronic Conference on Tropical Feeds Livestock Feed Resources within Integrated Farming Systems ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Abstract of thirtieth paper, from A. Nefzaoui. Questions that might stimulate discussion on this topic include: 1. Apart from the well-known use of Opuntia as a drought feed, is it a major fodder all year round in your area? If not, what are the constraints impeding this happening considering its very efficient use of water compared to other traditional fodders? 2. Do you have any data on ruminant diets based on Opuntia and fodder shrubs all year round? 3. Is the use of PEG for optimizing the fodder shrub/tree component of the ruminant diet economically and technically feasible in your area? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THE INTEGRATION OF FODDER SHRUBS AND CACTUS IN THE FEEDING OF SMALL RUMINANTS IN THE ARID ZONES OF NORTH AFRICA A. Nefzaoui INRA Tunisia, Rue Hedi Karray, Ariana 2049 Tunisia ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ABSTRACT In the arid and semi-arid zones of North Africa, animal feed resources are fluctuating and insufficient. Small ruminants are basically fed on rangelands. During the last three decades, the contribution of rangelands to the needs of livestock decreased from 80 to 30%. Therefore, to reduce the increasing deficit of feed resources and to preserve the rangelands, large scale plantations of spineless cactus (Opuntia ficus indica, var. inermis), Acacia (Acacia cyanophylla, Lindl.) and Atriplex (Atriplex nummularia and A. halimus) were established recently (400,000 hectares in Tunisia). The benefits of these species include high biomass yield, evergreen character, drought resistance, tolerance to salinity and soil adaptability. These plantations were first established mainly on communal lands but recently more and more were established on mixed crop/livestock farms and private land. Opuntia and shrubs are planted in wide rows allowing cereal cropping (mainly barley) in between. Animals may therefore graze the increased herbaceous biomass between the rows during spring, and stubbles during the summer time. The seasonal supply of feed is then better adjusted to the animals' needs, and livestock feeding is based more on farm resources than on commercial feeds. Indeed livestock farmers, and especially small herd owners, face dramatic difficulties during the frequent drought seasons. They are often forced to sell a large number of their flock in order to buy either rarely available expensive straw and hay or imported cereal-based feeds. Nutritionally, the above mentioned species complement each other. Opuntia, rich in water and carbohydrates, gives sufficient energy, Atriplex provides protein and Acacia is a fibre source. Nutritional characteristics of these species and their use in combination with other farm resources such as treated straw will be discussed. Opuntia pads have low crude protein (20 to 50 g/kg DM) and crude fibre (80 to 150g/kg DM) contents. However, they have high contents of water (800 to 900 g/kg fresh weight) and ash (150 to 250 g/kg DM). Cactus helps to meet the animals' water requirement. In addition, cactus pads are rich in vitamin A (almost the only source under harsh conditions) and in readily available carbohydrates. However, they need to be supplemented with nitrogen. On the other hand, poor quality diets may be correctly supplemented with cactus. Our work showed that the intake of straw increased significantly with the amount of cactus in the diet. Moreover, cactus is a good supplement to ammonia- or urea-treated straw because it provides the carbohydrates needed for the efficient use of non-protein nitrogen. Other trials clearly demonstrated that energy and nitrogen requirements of sheep may be met using cactus-based diets supplemented with Atriplex sp. Indeed, it is possible to get good performances by feeding animals cactus and Atriplex ad libitum with limited amounts of hay and barley. Such diets are recommended during drought years in arid and semi-arid zones. Diets based on limited amounts of straw (17%) and various amounts of Atriplex nummularia (24 to 59%) and spineless cactus (21 to 56%) can cover 165 to 180%, and 165 to 230% of the sheep's maintenance requirements, in energy and digestible crude protein terms, respectively. Such diets, using low inputs of cereal grains and forage crops, are recommended to cope with the feed deficiency prevailing in the North African arid and semi arid areas. Acacia cyanophylla Lindl. is a leguminous fodder tree that is widespread in North Africa. Acacia leaves are high in crude protein (14% DM), lignin (ADL, 16% DM) and condensed tannins (4,5% DM catechin equivalent). Their nitrogen is poorly digested by the animal because of the condensed tannins. Air drying or polyethylene glycol (PEG 4000) treatment help to overcome this problem. PEG may be added in drinking water or included in feed blocks in order to efficiently increase the performance of animals fed Acacia leaves. Trials were carried out with sheep to investigate the effect of air-drying and polyethylene glycol (PEG) treatment of Acacia leaves on intake, digestibility and growth. A decrease in condensed tannin content was observed when Acacia leaves were air-dried or treated with PEG. Drying and PEG treatment significantly increased nitrogen utilization. Crude protein digestibility of Acacia averaged 18.6, 17.2 and 68.8% for fresh, air-dried and PEG-treated leaves, respectively. The beneficial effect of PEG treatment was also supported by growth trials. KEY WORDS: Opuntia, prickly pear, nopal, Acacia cyanophylla, Atriplex, PEG, North Africa, feed, small ruminant ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~