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Yeheb (Cordeauxia edulis)

Datasheet

Description
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Common names 

Yeheb, yeheb bush, yeheb nut, ye'eb [English]; ኧህብ [Amharic]

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Related feed(s) 
Description 

Yeheb (Cordeauxia edulis Hemsl.) is a woody legume of the arid semi-deserts of Ethiopia and Somalia. It is a multipurpose shrub highly valued both for its nutritious nut, which is a staple food in the drier areas of the region, and as forage for livestock during the dry season. Yeheb plays an important role in the livelihoods of the local communities but it is currently considered as a vulnerable species (Yusuf et al., 2013). Yeheb is the only species of the genus Cordeauxia (Brink, 2006).

Morphology

Yeheb is a perennial, leguminous, evergreen, much-branched shrub (tree), 1.6 to 4 m tall (Orwa et al., 2009; NRC, 1979). It develops deep roots that tap soil moisture down to a depth of 3 m, and lateral roots that explore the soil layers between 10-40 cm, and down to 2.5 m. The stems are variable in diameter and are all bearing red dots (red glands). The leaves are alternate and paripinnate with 2-12 elliptic to oblong leaflets, 3-5 cm long x 1.5-2.5 cm wide. The leaflets are olive green in colour and bear conspicuous red glands on their lower surface. The limbs are covered with an extremely thick cuticle that protects the leaves from drought. The inflorescence is a terminal raceme bearing yellow, pentamerous, hermaphrodite flowers, 2.5 cm in diameter (Orwa et al., 2009; Brink, 2006). The fruit is an ovoid, slightly curved, dehiscent pod, 4-6 cm long x 2 cm wide. The pods contain 1-2 ovoid seeds, 2-4.5 cm long, with a thin easily cracked testa (Brink, 2006). It has been suggested that 2 varieties of yeheb (sulei and mogollo) exist in Somalia, distinguished by their stem, fruit and leaf sizes (Orwa et al., 2009). Mogollo seeds are claimed to be sweeter than those of sulei (Brink, 2006).

Uses

Yeheb is used as a source of staple food for nomad populations and as fodder for livestock (Yusuf et al., 2013). It is considered a famine food in Ethiopia (Guinand et al., 2001). The seeds ("nuts") are edible, much relished, and often compared to cashew nuts, almonds or chestnuts. They provide a balanced diet containing high energy (high fat and starch contents), and valuable protein with good amino acid content similar to that of legume crops, though deficient in methionine. They are eaten fresh, dried, roasted, boiled, made into a soup, or used as a coffee substitute (Yusuf et al., 2013; Brink, 2006). Yeheb nuts provide an oil used to make soap (Orwa et al., 2009; Brink, 2006; Guinand et al., 2001). The seeds are reported to have ethnomedicinal properties (Yusuf et al., 2013; Brink, 2006). The nectar of yeheb is favoured by bees, and the shrubs are used as living fences and for soil conservation (Yusuf et al., 2013; Vivero et al., 2005). Yeheb provides good firewood and timber, which is used in 90% of house constructions in areas where yeheb trees are still numerous (Yusuf et al., 2013; Orwa et al., 2009). Yeheb leaves and seeds contain the red dye cordeauxiaquinone (Söderberg, 2010). Leaf extracts form fast and insoluble dyes with metals and have been used as mordants in dyeing fabrics (NRC, 1979). Yeheb nuts are sold locally and in markets as a source of income for harvesters (Yusuf et al., 2013).

Yeheb is an outstanding source of fodder for many livestock species (camels, sheep, goats and cattle) during the dry season, and is sometimes the only available and palatable source of green forage during this period (Orwa et al., 2009; Brink, 2006). Local herders believe that yeheb prevents diseases in livestock (Yusuf et al., 2013).

Distribution 

Cordeauxia edulis is an endemic species from South-Eastern Ethiopia and Central Somalia. Yeheb is mostly found in the wild within its native range. In Somaliland, people have started to grow it and produce seedlings (Guinand et al., 2001). Yeheb was introduced into Kenya in the 1950s, and it has been experimentally introduced into Sudan, Tanzania, Yemen, Israel (Negev desert) and the USA (Brink, 2006; Nerd et al., 1990).

Yeheb grows in the wild in semi-desert regions of Ethiopia and Somalia, in Acacia-Commiphora deciduous bushland, from sea level to an altitude of 1000 m. It is found in places at 100 km of the Indian Ocean, at least. It cannot tolerate frost: it died at 4°C in Israel (Brink, 2006; Mizrahi et al., 2001). Preferred mean annual temperatures are 26-30°C, with an annual rainfall between 100 and 400 mm, including 4-5 month drought periods and 2 rainy seasons (Brink, 2006). Yeheb grows in a wide range of soils from deep coarse red sands to slightly alkaline (pH 6.7-8.4) poor soils, which are extremely deprived of N. Yeheb does not withstand waterlogging and it is thus never found in alluvial flats prone to water and silt collection (Orwa et al., 2009).

Forage management 

Establishment

Yeheb propagates from seeds in the wild. When cultivated, yeheb can be directly seeded, seeded and transplanted, or it can be propagated through stem cuttings. There is no information on optimum shrub densities and spacings. In natural stands, in Somalia, there is up to 320 shrubs/ha (Brink, 2006). The seeds should not be stored for long periods as they lose their viability after a few months. Coating in wood ash and sealing improve shelf-life (Brink, 2006). In order to increase shelf life beyond 2 years, storage should be at moderate temperature (16-20°C) with moisture ranging from 10 to 15% (Andersson et al., 2007). It might be helpful to plant seeds in small bags containing soil from the native area of yeheb as it may contain the appropriate inoculum for mycorrhizae (Ismail, 2016). It was shown in experiments that inoculation by either native soil or commercial microorganisms had a positive effect on plant growth (Mekonnen et al., 2010). Once planted, germination occurs rapidly but subsequent growth of green material is slow. A major constraint with seedlings is the quick development of the taproot which is prone to be broken during transplantation, which completely eliminates survival.

Cultivation

Yeheb responds positively to N and P fertilizer at 46-92 kg/ha and 8 kg/ha respectively (Mekonnen et al., 2011). The trees start fruiting around 4-5 years-old. Flowering occurs just before the rainy season. Once pollinated, the flowers drop and the fertilized ovaries develop only when rain occurs (they can remain undeveloped for 4-5 months). The time to fruit maturity is 14-15 days (Orwa et al., 2009; Brink, 2006). Fruits can be harvested twice a year if rainfall occurs in both rainy seasons. 

Yield

A yeheb tree can yield 5-8 kg seeds/year. Yeheb forage is of good quality compared to other plants, particularly during the dry season (Ali, 1988). Yeheb is resistant to heavy grazing because of its regrowth ability: plants heavily browsed tended to resprout profusely from the base (Ali, 1988). Yeheb can yield about 325-450 kg forage/ha (Brink, 2006).

Environmental impact 

Conservation status

Cordeauxia edulis has been overexploited since the 1930s, when it represented half of the woody vegetation of its native area. Due to many adverse conditions including repeated droughts, wars, and its high palatability for livestock, yeheb populations have decreased dramatically since that time. Yeheb was put in the "endangered category" of the IUCN Red list of endangered species in 1978, and has been reclassified as "vulnerable" in 1998. Its status now requires reassessment (IUCN, 2016). Yeheb specialists recommend to start its cultivation in arid areas to prevent the extinction of the species, but also to alleviate risks of food shortages in the drier areas of Africa (Ismail, 2016; Yusuf et al., 2013; Mizrahi et al., 2001; Miège et al., 1978; Bally, 1966; NRC, 1979). Regeneration and protection of natural stands and cultivation in afforestation programmes outside its native range have been recommended (Brink, 2006). A study in 2016, based on 10 villages in the Somali Regional State of Ethiopia (Eastern Ethiopia) where the only naturally occurring yeheb is to be found, reported that the plant population is diminishing and natural regeneration is negligible (Ismail, 2016). This "Yeheb project" intends to replant yeheb in 6 sites of Somaliland (Ismail, 2016).

Insecticide

Freshly picked roasted or boiled seeds are used to kill insects (Orwa et al., 2009). Leaf extracts from yeheb can be used to modify feeding behaviour and ovipositing of the diamondback moth (Plutella xylostella), a parasite of broccoli crops. So it could be used for integrated pest management and to alleviate damage caused by this moth (Egigu et al., 2010).

Nutritional aspects
Nutritional attributes 

Though yeheb is a legume plant, its protein content is rather low (8-14% of DM). Protein increased slightly from the vegetative to the flowering stage in the small-leaf form. The plant is richest in protein during flowering, with a slight decrease as the dry season advances (Ali, 1988). Moisture content is low even during the middle of growing season and declines to less than 30% during the dry season (Ali, 1988). The foliage is rich in fibre (ADF 26-38%), similarly to that of other tropical legume forages. The calcium content is high (more than 1% of DM), but phosphorus is low.

Potential constraints 

Cordeauxiaquinone

The cordeauxiaquinone contained in yeheb foliage stains the meat, bones and teeth of animals with a pinkish-orange colour. This is considered a sign of good quality in Somalia and Saudia Arabia and some herders claim the meat of animal having eaten yeheb to be more tasty (Brink, 2006; Orwa et al., 2009). However, the colouring is a problem when exporting meat abroad (Söderberg, 2010).

Tannins

Leathery leaves contain 2.5-2.7% tannins (Brink, 2006).

Trypsin inhibitors and other antinutritional factors

The seeds contain trypsin inhibitors (Yusuf et al., 2013; Brink, 2006; Miège et al., 1978). When they are eaten raw by humans, their high level of trypsin inhibitor limits protein absorption in the intestine and may thus cause nausea or stomach distress (Yusuf et al., 2013). Yeheb seeds are deprived of phytohaemagglutinins, which is an advantage over legume seeds (Miège et al., 1978).

Ruminants 

Yeheb is an important source of fodder for many livestock species (camels, sheep, goats and cattle) during the dry season. However, information about the use of yeheb by livestock is extremely limited. Calcium content is higher than cattle requirements but phosphorus content is insufficient (Ali, 1988).

Palatability

Yeheb leaves are leathery and not very palatable due to their tannin content, and livestock prefer other plants during the rainy season (Yusuf et al., 2013; Brink, 2006; Guinand et al., 2001). Animals that are newly introduced to yeheb may initially ignore it (Kuchar, 1987). A small study involving two goats noted that the animals did not find yeheb very palatable, especially the dried leaves, that were only consumed at 75% (Söderberg, 2010). However, yeheb is often the only palatable source of green forage left during the dry season (Yusuf et al., 2013; Orwa et al., 2009; Brink, 2006). 

Digestibility

In vitro DM digestibility of yeheb foliage was reported to be very low, in the 27-40% range (Ali, 1988).

Camels

Yeheb is mainly consumed by camels. Herders believe that yeheb foliage increases camels libido, and could, therefore, have a beneficial impact on herd size (Yusuf et al., 2013).

Goats

While a study conducted in 1939 reported that yeheb caused intestinal disorders in goats, recent investigations have found that goats fed yeheb remained healthy (Söderberg, 2010). 

Rabbits 

No references were available on the use of yeheb forage in feeding domestic rabbits (September 2016). Nevertheless, because the foliage of this leguminous brush is browsed by goats, sheep, cattle and camels (see Ruminants above), it could be considered as a potential forage for rabbits.

The risk of predation of young plantations by rabbits (Oryctolagus cuniculus) is absent in the original country of this plant, because of the absence of wild rabbits in North-East Africa (Azzaroli Puccetti et al., 1996; Assefa et al., 2008; Negeri et al., 2015). However, predation by other local lagomorphs (Lepus starki, L. habessinicus, L. fagani) cannot be ruled out (Mekonnen, 2007). The risk of predation by rabbits should be taken into account when introducing this shrub into other semi-desert areas of the world where rabbits are common.

Nutritional tables
Tables of chemical composition and nutritional value 

Avg: average or predicted value; SD: standard deviation; Min: minimum value; Max: maximum value; Nb: number of values (samples) used

Main analysis Unit Avg SD Min Max Nb  
Dry matter % as fed 43.1 12.1 26.9 54.1 10  
Crude protein % DM 11.2 1.6 7.9 14.2 12  
Crude fibre % DM 26.6   25.6 27.5 2  
ADF % DM 34.4 3.6 28.8 38.3 10  
Lignin % DM 10.1 1.1 7.9 11.4 10  
Ash % DM 6.6   6.2 6.9 2  
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 12.8 2.4 9.0 17.5 12  
Phosphorus g/kg DM 1.5 0.3 1.1 2.2 12  
Potassium g/kg DM 6.8   6.5 7.1 2  
Magnesium g/kg DM 1.5   1.1 1.8 2  
Manganese mg/kg DM 43   39 46 2  
Zinc mg/kg DM 23   21 24 2  
Copper mg/kg DM 11   8 14 2  
Iron mg/kg DM 587   438 735 2  
               
In vitro digestibility and solubility Unit Avg SD Min Max Nb  
DM digestibility, pepsin % 31.5 3.7 27.2 39.8 10  

The asterisk * indicates that the average value was obtained by an equation.

References

Ali, 1988; Drechsel et al., 1988

Last updated on 22/09/2016 14:36:13

References
References 
Datasheet citation 

Heuzé V., Thiollet H., Tran G., Lebas F., 2017. Yeheb (Cordeauxia edulis). Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. http://www.feedipedia.org/node/598 Last updated on March 7, 2017, 11:30

English correction by Tim Smith (Animal Science consultant)