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Congo grass (Brachiaria ruziziensis)

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Description
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Common names 

Congo grass, Congo signal, Congo signal grass, Kennedy ruzi, Kennedy ruzigrass, prostrate signal grass, ruzi, ruzigrass, ruzi grass [English]; Congo, Congo señal, gambutera, Kenia, pasto Congo, pasto ruzi, ruzi [Spanish]; ruzisiensis, capim congo [Portuguese]; herbe à bengali, ruzi [French]; rumput ruzi [Indonesian]; ya ruzi [Thai]

Synonyms 

Urochloa ruziziensis (R. Germ. & C.M. Evrard) Crins; Urochloa ruziziensis (R. Germ. & Evrard) Morrone & Zuloaga; Brachiaria decumbens var. ruziziensis (R. Germ. & Evrard) Ndab. (USDA, 2015; Quattrocchi, 2006)

Taxonomic information 

Many Brachiaria species, including Bracharia ruziziensis, have been placed by some authors in the Urochloa genus, so the taxon Urochloa ruziziensis (R. Germ. & C.M. Evrard) Crins is often considered as the correct one. However, these changes remain disputed and many recent papers still refer to Bracharia ruziziensis (Torres González et al., 2005).

Description 

Congo grass (Brachiaria ruziziensis Germ. & Evrard or Urochloa ruziziensis (R. Germ. & C.M. Evrard) Crins) is an important tropical forage grass.

Morphological description

Congo grass is a short-lived perennial grass (Husson et al., 2008). It is tufted, creeping (semi-prostrate) and rhizomatous. It roots from the nodes and forms a dense leafy cover (Cook et al., 2005Urio et al., 1988). Congo grass has a dense system of bunched, quickly growing roots that can go down to a depth of 1.8 m (Husson et al., 2008). Culms grow from the nodes of the rhizomes and may reach a height of 1.5 m when flowering (Cook et al., 2005). The leaves are soft but hairy on both sides, lanceolate in shape and up to 25 cm long x 1-1.5 cm broad, light-green in colour. The inflorescence consists of 3-9 relatively long racemes (4-10 cm) that bear spikelets in 1 or 2 rows on one side of a broad, flattened and winged rachis (Cook et al., 2005). The spikelets are hairy and 5 mm long. The weight of 1000 grains is about 4 g (Husson et al., 2008). Congo grass is very similar to signal grass (Brachiaria decumbens) and is often mistaken for it (Cook et al., 2005). Genetic material from Congo grass has been used to hybridize with Brachiaria brizantha yielding a series of cultivars known as Mulato (Argel et al., 2007Argel et al., 2005).

Uses

Congo grass is a valuable forage for livestock. It is palatable and its nutritive value is good (Schultze-Kraft et al., 1992). It is mostly used for direct grazing of permanent pastures, in the open or under coconut plantations. Congo grass can be cut for hay or fed fresh to stalled ruminants (Cook et al., 2005Schultze-Kraft et al., 1992). In Brazil, there is increasing interest in growing Congo grass both for fodder and for mulch in soybean-maize associations or in sunflower crops (Giancotti et al., 2015Ceccon et al., 2014).

Distribution 

Congo grass is native to the Ruzizi valley in the east of the Democratic Republic of the Congo, and to Rwanda and Burundi (Schultze-Kraft et al., 1992). In East Africa, Congo grass is one of the most important grasses of the Brachiaria (or Urochloa) genus, with bread grass (Brachiaria brizantha) and Para grass (Brachiaria mutica) (Urio et al., 1988). Though not as persistent as Brachiaria brizantha, Congo grass is the main Brachiaria grown in Thailand because seed production is easier (Partridge, 2003). Congo grass is naturalized in most humid tropics: West-Central Africa, western Indian Ocean, South-East Asia, the Pacific region, together with many countries of Western, Central and South America including Brazil (Clayton et al., 2006Schultze-Kraft et al., 1992).

In Africa, Congo grass is common as a pioneer species of cleared rain forest (Ecoport, 2014). It is generally found in grasslands from sea level up to an altitude of 2000 m in the humid tropics of Africa, and up to an altitude of 1200 m in Panama (FAO, 2015). It grows where annual rainfall is at least 1200 mm with a dry season of no more than 4-5 months (Cook et al., 2005Schultze-Kraft et al., 1992). Temperatures can range from 19°C to 33°C, although optimal growth is obtained when day/night temperatures are 33°C/28°C. Congo grass has no frost tolerance and only moderate shade tolerance. It does better in well drained fertile soils such as light to loam soils with a pH ranging from 5 to 6.8 (Cook et al., 2005). Congo grass has a low tolerance of waterlogging. In Brazil, some genotypes of Congo grass were found to have some aluminium tolerance (Miguel et al., 2011).

Forage management 

Yield

Congo grass is a summer growing species yielding large amounts of biomass with high N supply. DM yield exceeded 20 t/ha in Australia and South America, and up to 25 t DM/ha in Sri Lanka when 366 kg N/ha fertilizer were applied (Husson et al., 2008; Cook et al., 2005). In the low fertile soils of Coronel Pacheco (Brazil) with no N fertilizer, Congo grass yielded only 6 t DM/ha. However, biomass yields up to 12 t DM/ha were possible after applying 150 kg/ha N fertilizer (Cook et al., 2005). Biomass production is at its highest during the second year of establishment. Congo grass is markedly less productive than signal grass, which reduces its potential as a forage crop, particularly in low-fertile soils (Schultze-Kraft et al., 1992).

Forage management

Congo grass can be propagated both from root stock and from seeds (Urio et al., 1988). If propagation by seeds is intended, the dormancy of the seeds will be broken after 6 month storage, or by chemical scarification. Seeds can be broadcast on a well-prepared seedbed and should not be planted deeper than 2 cm. The vigour of Congo grass seedlings is high and prevents weed development (Husson et al., 2008). If Congo grass is vegetatively propagated, stem cuttings with rooting nodes are necessary. As Congo grass requires good soil fertility, it is important to provide N, P and K fertilizers prior to planting and during growth (Cook et al., 2005). Once it is established, and provided it receives enough N fertilizer, Congo grass spreads readily. Congo grass flowers later than signal grass (Schultze-Kraft et al., 1992). It should be cut before first flowering and then at six week intervals (ILRI, 2013). When grazed, Congo grass withstands limited heavy grazing (Cook et al., 2005).

Association with legumes

Congo grass can be grown in association with a wide range of legumes such as stylo (Stylosanthes guianensis), puero (Pueraria phaseoloides), greenleaf desmodium (Desmodium intortum), centro (Centrosema molle) and leucaena (Leucaena leucocephala). In mixed swards Congo grass should be heavily grazed so that the sward becomes open and allows legumes to establish and persist (Cook et al., 2005). When grown in association with stylo, both plants can be harvested together to make good quality silage (FAO, 2015). It is possible to make pure Congo grass silage with formic acid as an additive, the best quality being obtained with 2 L formic acid/t (Lowilai et al., 2002).

Environmental impact 

Cover crop, erosion and weed controller, soil conditioner

In Brazil, Congo grass provides both fodder to livestock and good mulch material in no-till soybean plantations and no-till soybean-maize crop rotations (Ceccon et al., 2014Lima et al., 2014). It was assessed in no-till sunflower crops where its high sensitivity to glyphosate provided rapid desiccation, and its high C:N ratio allowed the mulch to remain as a soil cover over an extended period (Giancotti et al., 2015). Congo grass has been used to control erosion in different situations. When used to make contour hedgerows around cassava crops in Asian hills, it was found to decrease cassava yields (Howeler et al., 1998). Congo grass was used as a cover crop to decrease soil temperature and conserve soil moisture in coffee plantations where temperatures were above 30°C (EDE. Consulting, 2015).

Soil nutrients recycling and phosphorus availability enhancer

Congo grass has a valuable nutrient recycling activity, and enhances soil properties (Calonego et al., 2013Garcia et al., 2013). Congo grass was reported to decrease soil P fixation through acid phosphatase activity and the promotion of P-metabolizing micro-organisms (Janegitz et al., 2013). It subsequently enhances soil P availability for the next crops (Janegitz et al., 2013).

Nutritional aspects
Nutritional attributes 

Congo grass is a useful forage in the humid tropics. Its nutritive value can be good, especially during the rainy season: different authors reported crude protein concentrations between 8% and 15% of DM, and NDF concentrations between 61 and 67% of DM (Ibrahim et al., 1995Herrero et al., 2001Meale et al., 2012). However, drought has an adverse effect on its nutritive value: in Cameroon, protein content decreased from 16 to 5%, and NDF and ADF increased from 71 to 76% and 34 to 48% of DM, respectively, between rainy and dry seasons (Tedonkeng Pamo et al., 2007). The nutritive quality of Congo grass hay is lower, with a protein content about 5% of DM.

Potential constraints 

Photosensitization

Cases of photosensitization have been recorded with Congo grass, though less frequently than with signal grass. Mortality rates reached 20-60% in light-skinned sheep grazing pastures dominated by Congo grass in 1980 and 1981. The sheep developed generalized necrosis and severe icterus (jaundice) (Pierre, 1984). In Brazil, outbreaks of hepatogenous photosensitization of sheep have been recorded (Nazario et al., 1985 cited by Riet-Correa et al., 2011; Purchio et al., 1988).

Ruminants 

Congo grass is a valuable forage for ruminants.

Green forage

Congo grass is a common pasture grass for ruminants in Central Africa, Thailand and Brazil. Palatability is good, but decreases with age. In vitro DM digestibility ranged between 38% (Meale et al., 2012) and 66% (Herrero et al., 2001), but decreased with the stage of growth. DM digestibility of fresh Congo grass averaged 57%, and protein digestibility 53% in sheep (Khanum et al., 2010). In situ OM, DM and protein degradabilities were reported to be 47%, 51% and 65%, respectively (Lopes et al., 2010; Ibrahim et al., 1995). It has been observed that early lactating Holstein cows eating 15 kg DM/d of a diet composed of 50% Congo grass and 50% concentrate produced 17 kg milk/d (Wanapat et al., 2012).

In Thailand, Congo grass in mixtures with legumes such as leucaena, lablab (Tudsri et al., 2001) or rice bean (Wanapat et al., 2012), is often grazed in order to support satisfactory milk yields in dairy cattle. In West Africa, combinations of Congo grass with centro and round leaf cassia (Chamaecrista rotundifolia) resulted in higher nutritive values and palatability indices than others grass-legume mixtures (Olanite et al., 2004).

Silage and hay

Congo grass can be preserved as silage or hay. OM digestibility of Congo grass hay ranged from 55% in cattle to 47% in sheep, and protein digestibility from 37% in cattle to 24% in sheep (Kawashima et al., 2006Kawashima et al., 2007). The supplementation of Congo grass hay with soybean meal improved DM intake and nutrient digestibility in cattle and sheep (Kawashima et al., 2007). In goats, voluntary feed intake of Congo grass hay was higher than that of the silage (Insung et al., 2004).

Rabbits 

Fresh grass

Congo grass is considered as a palatable fresh forage by rabbits being rich in fibre, but it is poor in protein (Ghosh et al., 2009). Congo grass, used with a concentrate, is a typical fresh forage for rabbits in countries such as Burkina Faso (Lebas et al., 1997) and India (Das et al., 2007Gupta et al., 2007). For growing or breeding rabbits, fresh Congo grass is fed in limited quantities, for example 50% of the daily DM intake (Das et al., 2006), or is distributed ad libitum with a limited quantity of concentrate (Gupta et al., 2007Das et al., 2007). When compared to other fresh forages such as rice bean (Vigna umbellata), soybean forage and Job's tears (Coix lacryma-jobi) (Gupta et al., 2007), or lettuce head residue (Lactuca sativa) and Mimosa pigra (Nakkitset et al., 2008), Congo grass gave the poorest growth performance, probably due to its low protein content, but otherwise it did not cause health problems.

Hay

Ground Congo grass hay can be used as a fibre source in balanced complete feeds at up to 22% of the diet (Bianospino et al., 2010). A this level of inclusion, it is possible to estimate a digestible energy content of 7.3 MJ/kg DM and a protein digestibility of 46-47% (Lebas, 2013).

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 25.0 8.1 7.0 51.3 273  
Crude protein % DM 9.1 3.5 2.1 17.1 355  
Crude fibre % DM 33.0 3.9 23.8 42.8 329  
NDF % DM 67.7 4.6 61.5 76.6 16 *
ADF % DM 38.9 3.3 31.9 45.2 21 *
Lignin % DM 5.5 2.3 2.9 11.2 19 *
Ether extract % DM 2.0 0.5 0.7 3.5 321  
Ash % DM 9.5 2.1 4.9 14.2 340  
Gross energy MJ/kg DM 18.0   18.0 19.2 2 *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 4.2 1.0 1.6 7.0 327  
Phosphorus g/kg DM 2.2 1.0 0.1 4.8 325  
Potassium g/kg DM 24.2 8.2 6.2 42.5 270  
Sodium g/kg DM 0.7 0.6 0.3 1.4 3  
Magnesium g/kg DM 2.8 0.8 1.1 4.7 267  
Manganese mg/kg DM 50 14 39 70 4  
Zinc mg/kg DM 33 12 20 48 4  
Copper mg/kg DM 6 3 3 9 4  
Iron mg/kg DM 437       1  
               
Amino acids Unit Avg SD Min Max Nb  
Arginine % protein 5.3       1  
Histidine % protein 1.8       1  
Isoleucine % protein 4.0       1  
Leucine % protein 7.4       1  
Lysine % protein 3.0       1  
Phenylalanine % protein 5.2       1  
Threonine % protein 4.9       1  
Valine % protein 5.2       1  
               
Secondary metabolites Unit Avg SD Min Max Nb  
Tannins, condensed (eq. catechin) g/kg DM 0.2       1  
               
Ruminant nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 55.7         *
Energy digestibility, ruminants % 53.2         *
DE ruminants MJ/kg DM 9.6         *
ME ruminants MJ/kg DM 7.7         *
Nitrogen digestibility, ruminants % 58.5 9.2 53.1 69.2 3  
a (N) % 53.4       1  
b (N) % 24.2       1  
c (N) h-1 0.060       1  
Nitrogen degradability (effective, k=4%) % 68         *
Nitrogen degradability (effective, k=6%) % 65         *

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

References

Abaunza et al., 1991; CIRAD, 1991; Herrero et al., 2001; Ibrahim et al., 1995; INFIC, 1978; Kambashi et al., 2014; Khanum et al., 2010; Lopes et al., 2010; Maia et al., 2014; Meale et al., 2012; Nakkitset et al., 2008; Nasrullah et al., 2003; Pozy et al., 1996; Scaut, 1959; Tedonkeng et al., 2007; Vicente Chandler et al., 1974; Wanapat et al., 2012

Last updated on 23/08/2016 21:11:10

Main analysis Unit Avg SD Min Max Nb  
Dry matter % as fed 89.5 4.3 81.4 95.4 41  
Crude protein % DM 4.6 1.0 2.5 6.7 42  
Crude fibre % DM 38.4 2.6 33.6 43.9 41  
NDF % DM 70.7   70.7 73.8 2 *
ADF % DM 44.9 1.3 43.0 45.5 3 *
Lignin % DM 6.9         *
Ether extract % DM 1.2 0.2 0.8 1.7 41  
Ash % DM 8.3 1.8 5.0 11.5 44  
Gross energy MJ/kg DM 18.0 0.8 17.5 19.2 4 *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 4.4 0.7 2.8 6.1 38  
Phosphorus g/kg DM 1.6 0.7 0.3 3.2 41  
Potassium g/kg DM 21.6 5.6 10.1 31.3 37  
Sodium g/kg DM 0.1       1  
Magnesium g/kg DM 2.1 0.5 1.4 3.0 37  
Manganese mg/kg DM 153       1  
Zinc mg/kg DM 23       1  
Copper mg/kg DM 4       1  
               
Ruminant nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 45.8         *
Energy digestibility, ruminants % 43.7         *
DE ruminants MJ/kg DM 7.9         *
ME ruminants MJ/kg DM 6.4         *

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

References

CIRAD, 1991; Kawashima et al., 2006; Kawashima et al., 2007; Zogang et al., 2013

Last updated on 23/08/2016 21:12:20

Main analysis Unit Avg SD Min Max Nb
Dry matter % as fed 70.9 12.8 59.6 90.3 5
Crude protein % DM 11.5 0.3 11.1 11.9 5
Crude fibre % DM 16.0 1.7 14.2 18.0 5
NDF % DM 48.2 *
ADF % DM 17.2 *
Ether extract % DM 8.6 0.4 8.1 9.1 5
Ash % DM 4.4 0.4 3.8 4.9 5
Gross energy MJ/kg DM 19.7 *
 
Minerals Unit Avg SD Min Max Nb
Calcium g/kg DM 1.2 0.7 0.4 2.0 5
Phosphorus g/kg DM 2.8 0.2 2.4 3.0 5
Potassium g/kg DM 6.2 1.7 4.0 8.0 5
Magnesium g/kg DM 1.7 0.2 1.5 1.9 5
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, ruminants % 62.7 *
Energy digestibility, ruminants % 61.2 *
DE ruminants MJ/kg DM 12.1 *
ME ruminants MJ/kg DM 9.9 *
 
Pig nutritive values Unit Avg SD Min Max Nb
Energy digestibility, growing pig % 65.0 *
DE growing pig MJ/kg DM 12.8 *

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

References

CIRAD, 1991

Last updated on 23/08/2016 21:13:19

References
References 
Datasheet citation 

Heuzé V., Tran G., Boval M., Maxin G., Lebas F., 2017. Congo grass (Brachiaria ruziziensis). Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. https://www.feedipedia.org/node/484 Last updated on April 25, 2017, 15:26

English correction by Tim Smith (Animal Science consultant) and Hélène Thiollet (AFZ)
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