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Slenderleaf (Crotalaria brevidens)

Datasheet

Description
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Common names 

Slenderleaf, rattlepod, rattle pea, Ethiopian rattlebox [English]; crotalaire, sonnette [French]; marejea [Swahili]

Synonyms 

Crotalaria albertiana Baker f., Crotalaria intermedia Kotschy, Crotalaria intermedia Kotschy var. abyssinica Engl., Crotalaria intermedia Kotschy var. dorumaensis (Wilczek) Polhill, Crotalaria intermedia Kotschy var. parviflora (Baker f.) Polhill, Crotalaria purpureo-lineata Baker f.

Feed categories 
Description 

Slenderleaf (Crotalaria brevidens Benth.) is a tropical legume mostly cultivated for food (Abukutsa-Onyango, 2004; Duke, 1981). Unlike other Crotalaria species, its toxicity level is regarded as low and it can safely be used for forage.

Morphological description

Crotalaria brevidens is an annual or short-lived perennial legume reaching a height of 0.4-2 m. It is erect or decumbent, and much-branched. The stems are ascending with short hairs. The leaves are alternate, trifoliolate and borne on 2-6 cm long petioles. The leaflets are linear to lanceolate, 4-14 cm long x 0.3-3.3 cm wide, hairy on their lower face. The inflorescences are apical racemes, 10-48 cm in length. They bear numerous, closely arranged papillonaceous, cream to clear yellow, veined reddish-brown flowers. The fruits are narrow, cylindrical, pubescent pods, 35-50 mm long x 5-7 mm broad, containing about 80 seeds. The seeds are smooth, small, 2-2.5 mm long x 1.5-2 mm broad, cordiform, very variable in colour (from medium yellow to orange yellow, red to dark brown or dark grey-blue. The 1000 seed-weight is 5 g (Abukutsa-Onyango, 2004; Duke, 1981).

Uses

Slenderleaf is mainly a food legume: young leaves and shoots are cooked as a leafy vegetable in the East African countries of Kenya and Tanzania. Slenderleaf can be boiled or fried, or used as a potherb in stews and soups (Abukutsa-Onyango, 2004). Elderly people like its bitterness but younger people prefer Crotalaria ochroleuca (rattlepod), a closely related species (Abukutsa-Onyango, 2004). Slenderleaf seeds can be used to produce a hydrophilic polysaccharide with thickening and sizing properties that compare with those of guar gum (Tookey et al., 1963).

Information on the use of Crotalaria brevidens as forage is scarce and most of it come from a series of evaluations carried out on Crotalaria species in Florida in the 1930s. Those evaluations concluded that slenderleaf was the best Crotalaria species for livestock though its palatability and nutritional value were not high (Neal et al., 1935; Ritchey et al., 1941). Slenderleaf was used in its native range in Africa for fodder at least until the 1960s (Dougall et al., 1966), and was part of a series of evaluations planned in Tanzania in the 1980s (Myoya et al., 1988). More recent data remain elusive and it is not known if slenderleaf is currently used for livestock.

Distribution 

Slenderleaf is native to tropical Africa. It occurs naturally from Northern Nigeria eastwards to Ethiopia and southwards to Southern Tanzania. It was introduced into Morocco, the West Indies and the Americas. It is cultivated as a vegetable in Sudan, Kenya, Uganda and Tanzania (Abukutsa-Onyango, 2004; Duke, 1981). Slenderleaf grows well in grasslands, deciduous woodlands and bushlands, in seasonally swampy grasslands and occasionally on termite mounds. It can also be found on cultivated ground, roadsides and in clearings of upland dry forests (Duke, 1981). Slenderleaf occurs in tropical and subtropical areas from sea level up to an altitude of 2700 m. It grows best on soils with pH ranging from 6-6.5, in sunny areas where annual daily temperatures are between 16-26°C, and where annual rainfall is in the 1400-2000 mm range. However, slenderleaf can still grow in harsher conditions, where the temperature is between 12 and 30°C, annual rainfall range about 1100-2700 mm and soil pH comprised within 5 and 7.5. Slenderleaf is not tolerant of frost and can be killed at -2°C, new growth being damaged at -1°C (Abukutsa-Onyango, 2004). Slenderleaf is a smallholder crop mostly marketed as a vegetable in East Africa (Abukutsa-Onyango, 2002).

Forage management 

Slenderleaf (Crotalaria brevidens) can be broadcast or drilled in rows 30 cm apart. The seedlings are thinned to a spacing of 15-20 cm x 15-20 cm after 6 weeks. It can be intercropped with finger millet.

Vegetable harvest

In Africa, slenderleaf is mainly harvested as a vegetable by uprooting the whole plant. The uprooted thinnings may be used as a first harvest and the remaining plants are ready just before flowering at about 8 weeks, when the stems are about 40 cm in height. Harvesting may continue for 4 months (Abukutsa-Onyango, 2004). Another method of harvesting is to cut the main shoot 10-15 cm above ground after 8 weeks and let new shoots grow over the next 2 weeks before picking. Up to 15 successive pickings can be done every 2 weeks until the dry season sets in and no further shoots develop. The plants are then uprooted (Abukutsa-Onyango, 2004). The leaf yield is about 10 t green matter/ha. A green manure crop yields about 20 t/ha of fresh organic matter.

This species has a symbiotic relationship with some soil bacteria. These bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant, and some can be used by neighbouring plants.

Hay and silage

Crotalaria brevidens should be harvested before the bud stage as it then becomes woody and unusable for forage. Slenderleaf ensiled satisfactorily when the DM of the green forage varied between 20 and 32% (Ritchey et al., 1941).

Environmental impact 

Soil improver and green manure

Slenderleaf (Crotalaria brevidens) is an N-fixing legume: it improves the N status of the soil and can be intercropped with finger millet crops, providing valuable N return to the next-year finger millet crop (Chweya, 1997). Slenderleaf does well on slopes and has been used in soil erosion control (Duke, 1981). In Brazil, slenderleaf has been used in coffee plantations as a green manure and cover crop. It prevented soil erosion by adding moisture and reducing soil temperature. Slenderleaf also reduced weed growth (Muzilli et al., 1992).

Striga hermonthica controller

Slenderleaf (Crotalaria brevidens) is reported to promote the germination of striga, a parasitic plant that is a major problem for maize and millet growers. In the presence of Crotalaria, striga germinates and later dies due to the lack of a suitable host plant (Abukutsa-Onyango, 2004).

Nutritional aspects
Nutritional attributes 

Crotalaria brevidens has a low protein content for a legume, with values ranging from 10 to 21% of DM (though one reported value reached 28%). It is notable for the rapid increase in fibre after the bud flowering stage when crude fibre can reach 50% of DM.

Potential constraints 

Unlike other Crotalaria species, Crotalaria brevidens contains very low amounts of pyrrolizidine alkaloids that are deleterious to humans and animals (Tookey et al., 1963). However, some of these toxic alkaloids have been detected (Uiso, 1991). A comparison of the palatability, feeding value and apparent toxicity for rats of 150 tropical legumes (Cassia, Crotalaria, Indigofera and Tephrosia species) found that Crotalaria brevidens resulted in poor or no growth and low intake, indicating toxicity and/or unpalatability (Strickland et al., 1986). In humans, it is possible that the elaborate cooking methods used to prepare slenderleaf for food actually result in detoxification (Uiso, 1991).

Ruminants 

Most of the information about the use of Crotalaria brevidens (or more precisely on Crotalaria brevidens var. intermedia) comes from a series of trials conducted in the 1930s in Florida. These trials compared several Crotalaria species for pasture, hay and silage and found that Crotalaria brevidens was the best Crotalaria species for fodder. However, the stage of development is an important factor in its palatability as the fibre content increases rapidly between the bud and pod stages, making the forage unusable (Ritchey et al., 1941).

Pasture

Crotalaria brevidens was grazed without much difficulty by cows (though it was less palatable than common pasture grasses) and came second after Crotalaria incana in palatability. In addition to its relative palatability, it had a delayed formation of fibre in stems, kept its leaves to late in the season and was able to recover with new growth when cut and grazed. However, the plant was unusable for forage after the first pods (Ritchey et al., 1941). A report from Kenya noted that it had the reputation of being palatable (Dougall et al., 1966).

Hay

When cut early and high above the lower axial buds, slenderleaf made palatable hay for cattle and still produced a limited second crop. However, it was difficult to make high quality hay due to extensive leaf shattering and a tendency to become coarse and stemmy. Hay harvested in the pod stage and offered as sole feed did not maintain the body weight of dry cows (Ritchey et al., 1941).

Silage

Slenderleaf silage was better accepted than silages of other Crotalaria species. Cattle showed a preference for it when it was harvested at the bud stage or earlier. It was totally accepted when ensiled at the pre-bud stage. In trials with dairy cows, 20% of silage made at the bud stage was refused, compared to 7% for maize silage, and 6% for alfalfa hay. Slenderleaf silage gave lower milk yields than alfalfa. The OM digestibility of the silage in steers was poor (32%) due to the low digestibility of crude fibre (Neal et al., 1935; Ritchey et al., 1941).

Poultry 

The seeds are reportedly used to feed poultry (Abukutsa-Onyango, 2004).

Horses and donkeys 

Mules given slenderleaf hay preferred that harvested before the bloom stage to more mature forage. 74% of hay harvested at the pod stage was rejected (Ritchey et al., 1941).

Nutritional tables

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 14.4 3.4 8.4 18.3 16  
Crude protein % DM 14.5 4.9 9.3 28.9 19  
Crude fibre % DM 28.9   22.1 35.7 2  
NDF % DM 50.7       1  
Ether extract % DM 2.6   1.9 3.3 2  
Ash % DM 8.4   6.9 9.9 2  
Gross energy MJ/kg DM 18.5         *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 5.8   4.4 7.2 2  
Phosphorus g/kg DM 3.0   2.7 3.3 2  
Zinc mg/kg DM 28 8 15 42 16  
Iron mg/kg DM 8 1 6 11 16  

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

References

Dougall et al., 1966; Sahou et al., 2014; Strickland et al., 1986

Last updated on 23/09/2016 13:19:02

Main analysis Unit Avg SD Min Max Nb  
Dry matter % as fed 92.6   91.7 93.4 2  
Crude protein % DM 10.9   10.8 10.9 2  
Crude fibre % DM 45.2   42.3 48.2 2  
Ether extract % DM 1.8   1.3 2.3 2  
Ash % DM 3.1   2.9 3.3 2  
Gross energy MJ/kg DM 19.8         *
               
Ruminant nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 44.8   40.6 49.1 2  
Energy digestibility, ruminants % 42.8         *
DE ruminants MJ/kg DM 8.5         *
ME ruminants MJ/kg DM 6.7         *
Nitrogen digestibility, ruminants % 45.0   42.6 47.5 2  

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

References

Ritchey et al., 1941

Last updated on 23/09/2016 13:21:15

Main analysis Unit Avg SD Min Max Nb  
Dry matter % as fed 25.1 4.7 19.3 32.7 9  
Crude protein % DM 12.7 1.6 10.1 15.7 9  
Crude fibre % DM 42.5 7.9 24.4 51.2 9  
Ether extract % DM 2.9 0.3 2.3 3.4 9  
Ash % DM 5.8 1.5 3.9 8.1 9  
Gross energy MJ/kg DM 19.5         *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 7.6 1.1 5.8 9.4 8  
Phosphorus g/kg DM 2.7 0.4 2.0 3.3 8  
Magnesium g/kg DM 3.4 0.9 2.0 4.4 8  
               
Ruminant nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 32.1       1  
Energy digestibility, ruminants % 30.6         *
DE ruminants MJ/kg DM 6.0         *
ME ruminants MJ/kg DM 4.7         *
Nitrogen digestibility, ruminants % 62.9       1  

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

References

Neal et al., 1935; Ritchey et al., 1941

Last updated on 23/09/2016 14:17:06

References
References 
Datasheet citation 

Heuzé V., Thiollet H., Tran G., 2017. Slenderleaf (Crotalaria brevidens). Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. http://www.feedipedia.org/node/315 Last updated on January 16, 2017, 14:15

English correction by Tim Smith (Animal Science consultant)
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