The establishment of sustainable production systems based on cactus may contribute to the food security of populations in agriculturally marginalized areas and to soil improvement. Cacti are some of the best plants for the reafforestation of arid and semi-arid areas because they can resist scarce and erratic rainfall and high temperatures. They present various alternatives for exploitation:
Opuntia species used for animal feeding are abundant, easy and cheap to grow, palatable and can withstand prolonged droughts. Such characteristics make these species a potentially important feed supplement for livestock, particularly during periods of drought and seasons of low feed availability. The majority of Opuntia plant biomass is pad material rather than fruits and it can be fed to livestock as fresh forage or stored as silage for later feeding. The importance of cacti became evident when research results showed cacti are capable of developing high productivity in water-stress regions, because of their high water-use efficiency and their above-ground productivity. In Tunisia under rainfed conditions and with no fertilizer application, spineless cactus yields were between 20 and 100 tonnes of cladodes per year, for an average rainfall of 150 and 400 mm per year, respectively (Figure 1).
Figure 1. Cactus (Opuntia ficus indica var. inermis)
yield according to rainfall in Tunisia (adapted from Montjauze et Le
Houérou, 1965)
Use of cacti for livestock feeding Cactus is not a balanced feed and should rather be considered as a cheap source of energy. Cladodes have a low crude protein content and consequently need to be supplemented by protein sources. They are also low in phosphorus and sodium. The combination of spineless cactus (Opuntia ficus indica var. inermis) with cereal straw is a nutritionally satisfactory solution for maintaining small ruminants in arid zones. Generally cacti are highly palatable. The gut fill value is low but, unusually, feeding cactus enhances intake of fibrous feeds (straw). This result is highly interesting because straw is the main feed source in arid environments of WANA. It is well established that besides its low feed value, straw intake is low. Combining straw with cactus increases straw intake and consequently animal performance. Feeding cactus helps resolve the problem of watering animals in arid environment Water is scarce in arid zones of the WANA region. Watering animals during summer time and drought periods is a real problem. Animals spend a lot of energy to reach water points. Moreover, rangeland degradation in the area surrounding water points is a serious problem. Therefore, the high water content of cactus pads is a positive criteria, and feeding this species helps water animals in dry areas. The research results show clearly that water intake is nil when cactus intake by sheep is about 300 g of dry matter. Sheep fed for a long period (400 to 500 successive days) with large amounts of cactus stopped drinking (Figure 2).
Storage; Grazing vs. Cut-and-carry
Since cacti stays evergreen, it is better to store the product in situ and to avoid expensive processes like silage making or drying, even if they are technically feasible. Supplementing poor quality roughages with cactus Poor quality roughage may be supplemented with cactus. Indeed, the intake of straw increases significantly with the increase of the amount of cactus in the diet. Cactus is also a good supplement to ammonia or urea-treated straw, since it provides the necessary soluble carbohydrates for the efficient use of the non-protein nitrogen in the rumen. Therefore, cacti may be used as a major component of diets containing cereal straws, it is only necessary to add appropriate supplements to overcome the nitrogen deficiency and to provide the fiber needed for normal rumen functioning. Atriplex: a nitrogen supplement for cactus Energy and N requirements in sheep may be matched using diets based on these two feeds. The level of cactus in the diet may reach up to 55 % on a DM basis, without any digestive side effect. It is advisable that small amounts of fibrous feed (straw, hay) be fed to animals before cactus. Better diet efficiency can be obtained if the mineral balance is improved. When fed to animals, cacti behave more like a sugar-rich foodstuff (similar to cereal grain or molasses). Cacti are highly palatable (an average of 6 to 9 kg for sheep and 50 to 80 kg for cattle). Spines are not a limiting factor because they are easy to remove. To feed cactus, a few simple rules should be considered:
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In
Central and South Tunisia, cactus plantations provide a large amount
of fodder for livestock and play a key role in natural resources conservation.
