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Swazi grass (Digitaria swazilandensis)

Datasheet

Description
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Common names 

Swazi grass, Swaziland finger grass [English]; digitaire du Swaziland [French]

Synonyms 

Digitaria didactyla Willd. (CJB, 2010).

Taxonomic information 

The taxonomic status of Digitaria swazilandensis relatively to Digitaria didactyla is unclear. The GRIN database considers those two species to be different (USDA, 2010) while Cook describes Digitaria swazilandensis as a subspecies or a cultivar of Digitaria didactyla (Cook et al., 2005).

Description 

Swazi grass (Digitaria swazilandensis Stent) is a tropical and subtropical grass of rather low nutritional value, used for pasture in southern Africa and other tropical regions, such as Australia and French Guyana.

Morphology

Swazi grass is a stoloniferous perennial grass, less than 20 cm high. It is poorly rhizomatous with a shallow root system and thin, long stolons rooting at the nodes. It is leafy, many branched and creeping. The leaves are green-bluish coloured blades, 3 cm long x 5 mm wide. The inflorescence bears two conjugate and sessile racemes.

Utilisation

As a pasture grass, Swazi grass can stand continuous grazing (Campbell et al., 2009) but it does not bear heavy grazing or trampling because of its thin stolons. In French Guiana, swazi grass stands are mainly grown in the vicinity of villages and farms, and are dedicated to weaning animals, convalescent animals, finishing cattle or post-calving cows (Huguenin, 2008).

Distribution 

Swazi grass is native to tropical and southern Africa: Malawi, Mozambique, South Africa, Swaziland, Zimbabwe, and from Mauritius and Reunion islands (Quattrocchi, 2006; Cook et al., 2005). It has spread within the tropics and subtropics (often under communal grazing or as a lawn grass) but its extent is limited because it has been primarily propagated by stolons (Campbell et al., 2009; Cook et al., 2005).

Swazi grass thrives on poor soils provided they are well-drained. It is very common on granitic, moderately acidic or saline soils. It is susceptible to Al3+. It is suitable for wet areas where annual rainfall ranges from 900 to 1800 mm. It is tolerant of shade, short flooding and short droughts (limited to 2 months), but drops its leaves in the latter case (Huguenin, 2008; Cook et al., 2005). Temperatures above 15°C are necessary for swazi grass to grow, frost making the leaves shrivel (Cook et al., 2005).

Forage management 

Swazi grass produces dense and pure swards (Huguenin, 2008; Quattrocchi, 2006; Cook et al., 2005) but has also the ability to combine well with a wide range of legumes, including Trifolium repens, Arachis, Aeschynomene, Stylosanthes, Lotus and Lotononis species (Campbell et al., 2009; Göhl, 1982). The average useful life of swazi grass pastures ranges from 6 to 9 years (Holmann et al., 2004). In low fertility soils, pure swards of swazi grass are invaded by Mimosa pudica and the sward is degraded. However, when adequately fertilized (around 200 kg N/ha), swazi grass yields 5-12t DM/ha and is a strong competitor for weeds such as Mimosa pudica because its leaves rapidly regrow after being cut or grazed (Campbell et al., 2009; Huguenin, 2008; Dias et al., 2000). Until now swazi grass has been mainly vegetatively propagated since it does not seed a lot. However, new cultivars are being assessed for seed production (Campbell et al., 2009).

Environmental impact 

Compatibility with other species

Under heavy grazing, swazi grass combines well with creeping and other native and introduced legumes, especially if superphosphate is applied. Companion species include the following legumes: Desmodium triflorum, Zornia maculata, Glycine spp., Arachis pintoi, Aeschynomene falcata, Stylosanthes guianensis, Lotononis bainesii, Chamaecrista rotundifolia and Trifolium repens.

Weed control

In Australia, swazi grass is the best pasture species competitor to control giant Parramatta grass (Sporobolus fertilis) (Officer et al., 1998).

Nutritional aspects
Nutritional attributes 

The nutritional value of swazi grass is low (Denis, 2001). The crude protein content is around 9.5-10% of the DM and fertilizer is needed to improve the crude protein content (Huguenin, 2008; Aumont et al., 1995; Béreau et al., 1985). However, mixing swazi grass (35-40%) with Calopogonium and Macroptilium legume species increased the protein content of the pasture up to 11-12% (Béreau, 1995). 

Ruminants 

Swazi grass is mainly used as pasture for cattle, especially zebu. In French Guiana it is well adapted and readily eaten by cattle (Béreau, 1995). Stocking rate must be limited and fertilizer applied regularly in order to maintain the pasture (Huguenin, 2008). Swazi grass should be used at a young stage (30 days) of regrowth (Xandé et al., 1977). In spite of its rather low overall nutritive value, its in vitro DM digestibility was found to be high (62%) and it has a higher energy content than several other tropical forages (Aumont et al., 1995).

Cattle 

In permanent grazing systems (5 head/ha), swazi grass without supplementation has sustained about 0.5 kg/head daily weight gain in zebu cattle. This result was even obtained over a long period, taking into account the deleterious effect of the dry season on animal performance (weight losses of about 100-200 g/day) (Béreau et al., 1992; Rouville et al., 1989). On a rotational management system of 28 days, with a 4.5 bullocks/ha stocking rate, over 500 g live weight gain can be expected (Cunha et al., 1975). During dry periods, swazi grass was able to maintain live weight where native or Bahia grass (Paspalum notatum) plus clover pastures failed (Campbell et al., 2009).

Sheep

For sheep, the voluntary DM intake of swazi grass varies from 53 to 72.4 g/kg W0.75, with highest values with very young grass (Aumont et al., 1995; Michalet-Doreau et al., 1979).

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 23.5 5.4 15.7 33.9 13
Crude protein % DM 9.9 3.0 4.9 14.7 19
Crude fibre % DM 26.9 3.7 20.4 32.2 13
NDF % DM 62.5 1.6 62.5 67.1 5 *
ADF % DM 31.9 2.5 28.4 39.1 18 *
Lignin % DM 3.6 0.8 3.6 6.6 6 *
Ether extract % DM 1.9 1
Ash % DM 8.9 2.2 5.2 11.7 19
Gross energy MJ/kg DM 17.9 *
 
Minerals Unit Avg SD Min Max Nb
Calcium g/kg DM 5.0 1.9 2.7 8.2 6
Phosphorus g/kg DM 2.7 1.2 1.6 4.6 6
Potassium g/kg DM 13.8 7.0 6.9 25.4 6
Sodium g/kg DM 1.1 0.8 1.5 2
Magnesium g/kg DM 3.2 1.0 1.8 4.4 6
Manganese mg/kg DM 95 75 115 2
Zinc mg/kg DM 26 20 32 2
Copper mg/kg DM 5 5 6 2
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, Ruminant % 69.8 3.4 58.0 69.8 6 *
Energy digestibility, ruminants % 66.7 *
DE ruminants MJ/kg DM 12.0 *
ME ruminants MJ/kg DM 9.7 *
Nitrogen digestibility, ruminants % 64.5 7.4 55.0 75.0 6

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

References

Aumont et al., 1991; CIRAD, 1991; INFIC, 1978; Xandé et al., 1989

Last updated on 24/10/2012 00:45:12

Main analysis Unit Avg SD Min Max Nb
Dry matter % as fed 91.9 1.2 90.5 92.5 3
Crude protein % DM 9.5 3.3 6.9 13.2 3
Crude fibre % DM 32.5 2.2 30.1 34.6 3
NDF % DM 67.8 *
ADF % DM 38.1 37.0 39.0 2 *
Lignin % DM 5.0 5.0 6.2 2 *
Ether extract % DM 1.3 1
Ash % DM 7.4 2.2 5.4 9.7 3
Gross energy MJ/kg DM 18.3 *
 
Minerals Unit Avg SD Min Max Nb
Calcium g/kg DM 4.9 4.9 4.9 2
Phosphorus g/kg DM 2.5 1.7 3.2 2
Potassium g/kg DM 11.5 9.0 13.9 2
Sodium g/kg DM 1.2 1
Magnesium g/kg DM 5.3 4.6 6.1 2
Manganese mg/kg DM 41 1
Zinc mg/kg DM 22 1
Copper mg/kg DM 5 1
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, Ruminant % 61.8 *
Energy digestibility, ruminants % 58.3 *
DE ruminants MJ/kg DM 10.6 *
ME ruminants MJ/kg DM 8.6 *

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

References

CIRAD, 1991; Elliott, 1956

Last updated on 24/10/2012 00:45:12

References
References 
Datasheet citation 

Heuzé V., Tran G., Hassoun P., 2016. Swazi grass (Digitaria swazilandensis). Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. http://www.feedipedia.org/node/454 Last updated on September 10, 2016, 0:04

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