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cladode intake (g dry weight day-1)

cladode intake (g dry weight day-1)

Figure 12.4. Influence of cladode consumption on daily water uptake by sheep. Data are from Ben Salem et al. (1996).

Nouty et al. 1988; Silanikove 1992). Thus, supplying livestock with water during the summer and during drought periods is crucial in the WANA region and other arid regions. Animals consume considerable energy to reach water points. Moreover, rangeland degradation in the area surrounding water points is a serious problem. Therefore, the high water content of cladodes is beneficial in dry areas. Cattle given abundant supplies of cladodes require little (Cottier 1934) or no (Woodward et al. 1915) additional water. Sheep fed for a long period (400 to 500 days) with large amounts of cladodes stop drinking (Roussow 1961; Harvard-Duclos 1969). Also, water intake by sheep on a wheat straw diet becomes extremely low when the daily intake of cladodes is 300 g dry weight day-1 or more (Fig. 12.4), consistent with other findings (Terblanche et al. 1971). Similarly, sheep on an Acacia cyanophylla diet require 1.2 liter water day-1 when supplemented with barley but only 0.6 liter day-1 when supplemented with cladodes (Ben Salem et al. 2002).

Some Practical Considerations

The method of utilization of cladodes for livestock will differ according to circumstances, such as available labor, facilities, and quantity of cactus available. Although grazing of cladodes in situ is the simplest method, it is not the most efficient and care should be taken so that the animals do not overgraze the plants. The harvested cladodes may be cut into small pieces or strips and fed in a confined area to limit wastage (Fig. 12.1C). The cladodes can also be cut into smaller pieces and mixed with hay or low-quality alfalfa to make silage (if no fruits are included, molasses is usually added), which is maintained anaerobically.

Cladodes fed in various forms can keep animals alive for long periods. To supplement cladodes fed ad libitum, alfalfa or hay can provide protein and a lick of equal parts by mass of bone meal, salt, and fodder lime can provide phosphate and sodium (De Kock 1983).

It is cheapest to store cladodes as parts of living plants instead of after harvesting. Once harvested, chopped cladodes can be dried and then ground, e.g., using a ham-mermill with a sieve having 6-mm-diameter pores. Cladodes in the form of meal are not only more easily ingested but also are easier to store for use during droughts. Good quality silage can be made by chopping the pads together with oat straw, low-grade lucerne hay, or other roughage using 84 parts by mass of cladodes and 16 of roughage with the addition of 2% molasses.

The easiest and cheapest way to utilize platyopuntias is grazing. However, overgrazing of the plantation must be guarded against. Young plants are especially susceptible to overgrazing and can be killed by sheep. Even older plants can be so badly damaged that the subsequent production will be considerably lower. The best method for grazing is to divide the plantation into small paddocks and to graze each of these intensively for a few months every 3 years or so. Direct browsing necessitates a very tight control on grazing, otherwise wastage may reach 50% of the fodder produced (cladodes partially eaten and abandoned) and the plantation itself may be destroyed by overbrowsing (Monjauze and Le Houérou 1965; De Kock 1980). This type of management has a very low cost and the grass between the shrubs is available to the stock. Plants in a paddock can be grazed to one cladode higher than the original planting so that the plants recover well, the material used is of good quality, and the plants are kept within a usable size. Zero grazing—the cut-and-carry technique—has the opposite consequences. Loss of feed is virtually nil and risk of overutilization is small, except when young plantations are harvested too early. Even though the zero-grazing technique is labor-intensive, in most cases in North Africa it is the recommended method because of insufficient grazing discipline.

Although spineless O. ficus-indica is easiest to use, cladodes with spines are also valuable feed provided the spines are singed off first, usually through the use of a propane burner (Shoop et al. 1977). In Texas and Mexico, the standing plant is singed, whereas in North Africa detached cladodes are singed and then chopped into small pieces by hand (Fig. 12.1B) or machines. Steaming to moisten the spines and chopping of large pads can also facilitate the consumption of cladodes by livestock (Griffiths 1905).

Integration of Platyopuntias with Other Feed Resources in the WANA Region

In the WANA region climatic conditions lead to two feed gaps each year (Table 12.1): (1) in the winter (2-4 months) and (2) an even larger one in the summer plus autumn (56 months). These gaps require large amounts of supplemental feed. National strategies aimed to increase rangeland productivity have focused on highly producing species, such as Acacia cyanophylla, Atriplex nummularia (or A. halimus), and spineless platyopuntias. Several techniques for planting shrubs and cacti are used: (1) on communal rangelands, where introduced species are planted in rows without removal of natural herbaceous or woody natural species; (2) on private land an alley-cropping technique is preferred, where farmers can cultivate the area between rows when the rainfall conditions are favorable; (3) when soil conservation is crucial (Fig. 12.3), plantings are done for both types following the contour lines; and (4) the oldest type ("bosquet") involves a dense planting of platyopuntias around the house for fruit and for fodder for animals. Clearly, integrating platyopuntias with other resources in the feeding system is beneficial.

Poor-quality roughage may be supplemented with cladodes of Opuntia ficus-indica var. inermis. Indeed, the intake of straw goes up significantly with the increase of the amount of cladodes in the diet (Nefzaoui et al. 1993; Ben Salem et al. 1996). Cladodes are also a good supplement to ammonia- or urea-treated straw, because they provide the necessary soluble carbohydrates for the efficient use of nonprotein nitrogen in the rumen (Nefzaoui et al. 1993). For Barbarine sheep, voluntary intake of cladodes (presented ad libitum) remains high (450 g dry weight day-1) when 250 or 480 g day-1 of untreated, urea- or ammonia-treated straw is ingested (Nefzaoui et al. 1993). Diets containing 64% cladodes and straw cause no digestive disturbance. Maintenance energy requirements for sheep are met with the low level of straw intake, and for high level the energy intake is 80% above the maintenance level. Urea- or ammonia-treated straw is necessary to reduce the nitrogen deficit. When the untreated straw plus cladode diet is supplemented with Atriplex nummularia (about 300 g dry weight day-1) as the nitrogen source, even more nitrogen is retained in the sheep and the digestibility of organic matter and crude protein exceeds 70% (Nefzaoui and Ben Salem 1996). For 4-month-old lambs, when cladodes replace the more expensive barley grain, 10 to 15% more organic matter is taken up and daily weight gain averages 15% higher (Table 12.5). Platyopuntias such as O. ficus-indica can also be important for goats raised under

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