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Red oat grass (Themeda triandra)

Datasheet

Description
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Common names 

Red oat grass, kangaroo grass [English]; rooigras [Afrikaans]; واش سرخ [Persian]

Synonyms 

Anthistiria australis R. Br., Anthistiria imberbis Retz., Themeda australis (R. Br.) Stapf, Themeda forskalii Hack., Themeda imberbis (Retz.) T. Cooke

Related feed(s) 
Description 

Red oat grass (Themeda triandra Forssk.) is a tufted perennial grass of highly variable size, 30-180 cm tall with tussocks up to 0.5 m wide (Ecocrop, 2011; FAO, 2011; Liles, 2004). The culms are slender, erect and many-branched (Quattrocchi, 2006). The tussocks may be more or less leafy. The leaves, 10-50 cm long and 2-5 mm wide, are initially green to grey, and become a characteristic orange-brown in summer (Quattrocchi, 2006; Liles, 2004). The inflorescence is a narrow panicle up to 45 cm long that bears several pendulous racemes with large red-brown spikelets. Each raceme is surrounded by a leaf-like spathe (SANBI, 2011). The 4-7 cm long black awns remain with the seed when it falls (Liles, 2004). Red oat grass tends to be shorter and dark purple at higher altitudes and often lighter coloured and flushed only with purple at lower altitudes (SANBI, 2011).

Red oat grass is mainly used as fodder, but the grain can be eaten by people, particularly during times of famine (NRC, 1996). Red oat grass stems and leaves are used for pig bedding, and provide fibres for paper, basketry and thatching (Quattrocchi, 2006). Due to its colour and texture, it is an ornamental species in Australia (SANBI, 2011; Liles, 2004).

Red oat grass is an important grazing grass for domestic livestock and wildlife, and is part of the natural savannah pastures. It is highly palatable to livestock, especially when young (SANBI, 2011; Tothill, 1992). In Australia, it is grazed by kangaroos, rabbits and deer (Cole, 2003). Red oat grass is best grazed when 70% of the grass is green, about six weeks after the grass start its growth, for a 4-week period during short rains and for a 6-week period during the long rains (FAO, 2011).

Red oat grass is susceptible to heavy grazing and it may suffer a greater risk from overgrazing when other species have declined (Tothill, 1992). Reducing stocking rates may not allow Themeda populations to recover fast enough due its palatability (Ash et al., 1998). Rotational grazing is recommended. In southern Africa, an early summer (rather than late summer) rest period gives the highest dry matter and crude protein yields, root growth reserves and flowering culms (FAO, 2011).

Red oat grass cut for hay should be harvested at the end of the growing season. Dry matter yields are usually between 0.5 and 5 t/ha. Frequent cuttings should be avoided since they shorten the life of the stand (Ecocrop, 2011). An eight-week cut provides maximum DM yield, and this cutting interval increases DM yield by 60% compared to a two-week interval (Coughenour et al., 1985).

Red oat grass can be combined with other forage species such as Heteropogon contortus, Digitaria spp., Cymbopogon pospischilii, Dichanthium insculptum and Pennisetum mezianum (Kinyamario et al., 1992; Denny et al., 1980).

Distribution 

Red oat grass is the most common grass in the natural grasslands of Africa. In East Africa it represents 16% of the grasslands. It is a common species of the tropical and subtropical savannas and it also grows in temperate areas as a summer grass. In addition to its native Africa, it can be found in Australia, Tasmania, Papua New Guinea, South-East Asia and India (Tothill, 1992).

It grows from sea level up to an altitude of 3000 m, in warm-wet or cool-dry climates with moderate to high rainfall (500-800 mm to 6250 mm) (SANBI, 2011; Tothill, 1992). It keeps growing during the warm and cool seasons in the subtropics, which is an exception among andropogonoid grasses (Tothill, 1992). Red oat grass grows in pure stands on lateritic red earths (latosolic soils) of poor structure, low in lime, phosphorus and potash (FAO, 2011). It can also grow on a wide range of other soils, including loose sandy soils and alluvial silts, but does not stand heavy clays (Tothill, 1992). It prefers soils with high organic matter content (SANBI, 2011).

Red oat grass has some drought tolerance (FAO, 2011; Liles, 2004) and good drainage improves its ability to develop in a pasture (FAO, 2011). It is sensitive to flooding (Ecocrop, 2011). It grows in full sun to part shade (Liles, 2004). It can survive fires since its seeds are naturally buried down to 2.5 cm depth and are not affected by fire. A fire followed by a rain favours red oat grass since it increases its seed germination in conditions where others seeds die (FAO, 2011; Göhl, 1982). It is not found where protection from fire occurs (Göhl, 1982).

Environmental impact 

Bio indicator

Red grass is an indicator of veld being in a good condition: it quickly disappears if overgrazing occurs (SANBI, 2011; Quattrocchi, 2006; Heady, 1966). Red oat grass is a fire climax species, one of the first plants to grow after a fire, and all the more resistant to fire if it is burnt regularly and not overgrazed after germination (SANBI, 2011).

Red oat grass is also a pioneer plant in termite mounds (Smith et al., 1998).

Nutritional aspects
Nutritional attributes 

Red oat grass composition varies considerably: stage and grazing intensity are the main sources of variation (Heady, 1966). Its crude protein content is rather low, from 8-9% DM at the vegetative stage to 2-3% when mature. The NDF content is high and increases with maturity, from 65% at the vegetative stage to 70% at maturity (Feedipedia, 2011).

Potential constraints 

None reported (2011).

Ruminants 

Palatability

Red oat grass palatability is fairly good when young but the grass becomes unpalatable when mature. Plant stemminess and low leaf protein content have negative effects on acceptability by animals (O'Reagain et al., 1989). Cattle selectivity (by defoliation) is higher for red oat grass than for other Australian perennial grass species: cattle were less selective at the beginning of the rainy season, when red oat grass post-fire growth was short, and were most selective at the end of the rainy season when herbage was more stemmy and mature (Andrews, 1986).

Nutritive and feeding values

Available data on in vivo organic matter digestibility (OMD %) are scarce. The average from 3 available values is 54 ± 6% which corresponds to a ME content of 1.8 ± 0.3 Mcal/kg DM.

The crude protein content of the hay (3.4% DM in a 4 month-old stand) does not meet the requirements of grazing animals and needs supplements to improve animal performance (FAO, 2011).

Intake

Red oat grass intake rate in sheep and steers is similar to that obtained with 6 other low quality forages from the South African sourveld (areas with low levels of soil N and P) (O'Reagain et al., 1996). It compares favourably with Hyparrhenia rufa and Tristachya leucothrix when it is offered to animals during winter (Hatch et al., 1993). An intake trial with Boran cattle at EAAFRO (Kenya) reported a DM intake of 70.8 ± 2.6 g/kg W0.75 (Karue, 1975).

Stocking rates

Several studies have assessed the influence of red oat grass pasture stocking rate on animal performances. Data and recommendations are not consistent and are recorded in the table below:

Animal Weight Surface Conditions Reference
Cattle 350 kg LW 5 ha/head short rains in Kenya Karue, 1975
Cattle (adult+calf) 250 kg +100 kg 1 ha/head long rains in Kenya Karue, 1975
Cattle 250 kg 5 ha/head year long, Kenya Henderson et al., 1959
Boran steers unknown 1.76 ha/head to 5.2 ha/head 2 years, bimodal rainfall, Kenya McKay, 1971a
McKay, 1971b

Interactions between stocking rate and method of grazing were also studied. Live-weight gain was lower under a three-paddock/one-herd deferred rotation than it was with continuous grazing at 1.76 and 2.8 ha/head (McKay, 1971a; McKay, 1971b). In Uganda, under continuous grazing, lower stocking rates (2.4 ha/head vs. 0.6 ha/head) resulted in higher live-weight gains (0.4 kg/head/day vs. 0.3 kg/head/day) (Harrington, 1973). However, in order to maximize profits, a stocking rate of about 0.8 ha/head was recommended (Harrington et al., 1974a).

Supplementation at grazing

Red oat grass as the sole roughage could not sustain the requirements of a grazing animal, and it was recommended to give a supplement to improve animal performances (Karue, 1975). Supplementing red oat grass during winter with maize meal, molasses meal and urea improved live-weight gain and cumulative feed intake of Boer goat bucks (Almeida et al., 2006).

Burning and grazing

Burning the pasture reduced pasture yield in the subsequent wet season by about 40% but the quality and accessibility of the forage in the early wet season, in particular, was better. This contributed to better wet season growth of cattle grazing the previously burnt pastures (Winter, 1987).

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 47.0 7.2 36.0 58.4 12
Crude protein % DM 5.7 1.6 3.3 9.0 26
Crude fibre % DM 33.7 2.1 30.0 37.7 26
NDF % DM 69.0 *
ADF % DM 39.4 *
Lignin % DM 5.3 *
Ether extract % DM 2.1 0.5 1.4 3.0 24
Ash % DM 11.6 2.2 8.3 15.3 26
Gross energy MJ/kg DM 17.5 *
 
Minerals Unit Avg SD Min Max Nb
Calcium g/kg DM 2.7 1.1 1.2 4.9 23
Phosphorus g/kg DM 0.9 0.3 0.5 1.5 23
Potassium g/kg DM 6.9 3.1 3.1 13.7 23
Sodium g/kg DM 0.5 0.2 0.1 0.9 18
Magnesium g/kg DM 1.8 0.4 1.1 2.9 23
Manganese mg/kg DM 81 44 23 200 18
Zinc mg/kg DM 21 6 12 29 18
Copper mg/kg DM 5 1 4 7 18
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, Ruminant % 62.1 *
Energy digestibility, ruminants % 59.4 *
DE ruminants MJ/kg DM 10.4 *
ME ruminants MJ/kg DM 8.4 *
Nitrogen digestibility, ruminants % 51.9 1

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

References

Botha, 1938; CIRAD, 1991; Marshall, 1967

Last updated on 24/10/2012 00:44:54

Main analysis Unit Avg SD Min Max Nb
Dry matter % as fed 91.6 1
Crude protein % DM 4.4 1
Crude fibre % DM 40.4 1
NDF % DM 75.2 *
ADF % DM 46.7 *
Lignin % DM 6.9 *
Ether extract % DM 1.6 1
Ash % DM 10.3 1
Gross energy MJ/kg DM 17.8 *
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, Ruminant % 52.3 *
Energy digestibility, ruminants % 49.0 *
DE ruminants MJ/kg DM 8.7 *
ME ruminants MJ/kg DM 7.1 *
Nitrogen digestibility, ruminants % 10.5 7.4 13.5 2

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

References

Marshall, 1967; Todd, 1956

Last updated on 24/10/2012 00:45:35

References
References 
Datasheet citation 

Heuzé V., Tran G., Sauvant D., 2015. Red oat grass (Themeda triandra). Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. http://www.feedipedia.org/node/367 Last updated on October 5, 2015, 10:03

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