Jack bean (Canavalia ensiformis)

Jack bean, horse gram, chickasaro lima bean, overlock bean, Brazilian broad bean, sword bean (Australia), one-eye-bean (West Indies) [English]; feijão-de-porco [Portuguese]; fève Jacques [French]; frijol espada [Spanish]; Jackbohne, Madagaskarbohne, Riesenbohne [German]; Kacang parang [Indonesian]; Pwa maldyòk [Haitian Creole]; タチナタマメ [Japanese]; Канавалия мечевидная [Russian]; 矮性刀豆 [Chinese]

Canavalia ensiformis (L.) DC. [Fabaceae]

Canavalia ensifolia (DC.) Makino, Canavalia gladiata DC. var. ensiformis DC., Dolichos ensiformis L.

Jack bean (Canavalia ensiformis (L.) DC.) is a climbing perennial legume commonly cultivated as an annual. It grows up to 2 m high with 8-20 cm long trifoliate leaves and a strong root system. Flowers are pink, mauve or white with a red base. Pods are up to 36 cm long and contain 1-2 cm long, ellipsoid seeds. Pods and seeds are edible and used for food, the young pods being cooked as a vegetable. The whole plant, the pods and seeds are also used to feed animals.

The jack bean is native to tropical Africa and to South and Central America but is naturalized and cultivated worldwide (USDA, 2009; Chee et al., 1992). While it thrives in humid lowland tropics, it can also be found at altitudes up to 1800 m. Optimal annual rainfall is between 800-2000 mm but its deep rooting system allows it to withstand dry periods. It is reported to be tolerant to waterlogging and salinity (Ecoport, 2009). Jack bean has been reported as being antagonistic or suppressive of nematodes, particularly when used for intercropping in banana plantations (Vargas-Ayala et al., 2000), but this effect is disputed (Ternisien et al., 1989; Kashaija et al., 2004).

Jack bean is used in conservation agriculture with maize and cassava. It is generally recognized as a soil improver. In Mauritius, it is ploughed in for green manure for sugar cane after flowering (FAO, 2009).

The whole plant, the pods and the seeds are used to feed animals.

Jack bean seeds and foliage contain several antinutritional factors: concanavalin A (a lectin protein used in biotechnology), canavanine (a structural analogue of arginine) and canatoxin. Fresh forage and raw seeds are generally detrimental to animals. Cattle consuming too much seed meal develop symptoms such as fever, nasal discharge, lameness and prostration (Chee et al., 1992). It has been shown that 28 g of seed per 0.73 kg body weight are lethal to cattle (FAO, 2009). Dehulling, heat treatments and soaking have been recommended in order to lower the level of antinutritional factors. The seeds show urease activity likely to release ammonia: it is recommended to avoid using it with urea-treated feed in ruminant diets.

Foliage

Fresh forage is not palatable to ruminants and is eaten only in small amounts. However, cattle can gradually get used to it and acquire a taste for it (Chee et al., 1992). Drying results in higher intake. In goats, jack bean forage has been found worth considering for a dry season feed strategy in Nigeria (Akingbade et al., 2007).

Seeds

In cattle, diets containing 30% of jack bean seeds have an adverse effect on average daily gain (8.3% decrease). Supplementing grazing dairy cows with ground pods had no depressive effect on milk yield (Paredes et al., 1984). In sheep, increasing the inclusion rate from 22% to 32% resulted in lower rumen fermentation (Mora et al., 1986). In pre-weaning calves, supplementation with jack bean seeds resulted in lower daily live-weight gain compared to soybean meal and maize-based diets (Troccoli et al., 1989).

In growing pigs, Canavalia seeds were found to have a negative effect on average daily gain however they were processed (raw, alkali-treated, autoclaved or extruded) and the level of inclusion (5 to 15%) (Risso et al., 1992). However, diets containing up to 20% toasted seeds (at 194°C for 18 minutes) were not detrimental to feed intake and weight gain (Michelangeli et al., 2004).

Raw seeds, even at inclusion levels as low as 5%, have negative effects on broilers (decreased weight gain, increased feed conversion ratio, alterations in the liver, pancreas and kidneys) (Akinmutimi, 2006; Akanji et al., 2007b; Ologhobo et al., 2003). For this reason, it is recommended to process the seeds before feeding them to animals in order to reduce the antinutritional factors. However, autoclaving alone is not sufficient to mitigate deleterious effects of Jack bean. It may thus be useful to combine soaking and autoclaving or boiling, soaking and shaking (Belmar et al., 1999). The following table summarises the suggested methods and maximum inclusion rates.

Inclusion rates of Canavalia ensiformis seeds in poultry diets

Jack beans can be used to supplement rabbit diets but processing is recommended. Soaked and cooked jack bean enhances feed intake, growth rate and the feed/gain ratio (Bamikole et al., 2000; Udedibie et al., 2005). However, the muscles of rabbits fed on 30% soaked jack bean were fatter and contained less protein (Udedibie et al., 2005). The following table presents the inclusion rates found in the literature.

Inclusion rates of Canavalia ensiformis seeds in rabbit diets

Jack bean seed meal has been recommended as a protein source for Nile tilapia fingerlings. Cracking followed by cooking allowed for a 20% inclusion rate, and cooking in a trona solution made up to 30% seed meal in the diet possible (Fagbenro et al., 2004).