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Rhodes grass (Chloris gayana)

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Description
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Common names 

Rhodes grass, abyssinian Rhodes grass, Callide Rhodes grass, common Rhodes grass [English]; chloris, herbe de Rhodes [French]; capim de Rhodes [Portuguese]; grama de Rodas, pasto de Rodas, pasto Rhodes, zacate gordura [Spanish]; rhodesgras [Afrikaans]; koro-korosan [Philippines/Tagalog]; banuko [Philippines/Ilokano]; 非洲虎尾草 [Chinese]; アフリカヒゲシバ [Japanese]

Synonyms 

Chloris abyssinica Hochst. ex A. Rich.

Description 

Rhodes grass (Chloris gayana Kunth) is an important tropical grass widespread in tropical and subtropical countries. It is a useful forage for pasture and hay, drought-resistant and very productive, of high quality when young.

Morphology

Rhodes grass is a perennial or annual tropical grass. It is a leafy grass, 1-2 m in height, highly variable in habit. The culms are tufted or creeping, erect or decumbent, sometimes rooting from the nodes. The roots are very deep, down to 4.5 m. The leaves are linear, with flat or folded glabrous blades, 12-50 cm long x 10-20 mm wide, tapering at the apex. The seed head has an open hand shape and encompasses 2-10 one-sided or double-sided racemes, 4-15 cm long. The inflorescences are light greenish brown (rarely yellow) in colour, and turn darker brown as they mature (Cook et al., 2005). The spikelets (over 32) are densely imbricated and have two awns. The fruit is a caryopsis, longitudinally grooved (FAO, 2014; Quattrocchi, 2006; Moore, 2006; Cook et al., 2005; Duke, 1983).

Utilisation

Rhodes grass is primarily a useful forage of moderate to high quality. It is grazed, cut for hay or used as deferred feed but it is not suitable for silage. It can form pure stands or is sown with other grasses or legumes. Many cultivars have been developed in order to suit different cultivation conditions or end-uses, such as early, late and very late flowering cultivars (NSWDPI, 2004). Prostrate cultivars are suitable for grazing and erect cultivars are adapted to hay (FAO, 2014; Quattrocchi, 2006; Cook et al., 2005; Duke, 1983; Göhl, 1982). Chloris gayana is useful as a cover crop and soil improver, as it improves fertility and soil structure and helps to decrease nematode numbers (Cook et al., 2005).

Distribution 

Chloris gayana originated from Africa and is now widespread in tropical and subtropical areas worldwide. It was introduced into India, Pakistan, Australia and the USA. In Australia, it was introduced by soldiers returning from the Boer wars at the beginning of the 20th century. In Western Australia, Rhodes grass has become one of the most widely sown subtropical grasses since 2000 (Moore, 2006).

Rhodes grass is a spring and summer-growing grass found in open woodlands and grasslands, in road margins, disturbed sites and river banks. It is cultivated in sown pastures in irrigated terraces (Quattrocchi, 2006; Cook et al., 2005). Its latitudinal range is between 18-33°N and S, and it grows from sea level up to 2000-2400 m in equatorial areas, and up to 1000 m in subtropical areas (Ecocrop, 2014; Mengistu, 1985). Chloris gayana thrives in places where annual temperatures range from 16.5°C to above 26°C, with maximum growth at 30°C/25°C (day/night temperature). Optimal annual rainfall is about 600-750 mm with a summer-rainfall period (Ecocrop, 2014; Moore, 2006; Cook et al., 2005). Rhodes grass can survive in areas where annual rainfall ranges between 310 mm and 4030 mm and where temperature extremes are 5°C and 50°C (Cook et al., 2005; Duke, 1983). Due to its deep roots, Rhodes grass can withstand long dry periods (over 6 months) and up to 15 days of flooding (FAO, 2014; Cook et al., 2005). Seasonal waterlogging over 30 cm kills the plant (FAO, 2014). Some cultivars are tolerant of frost. Rhodes grass grows on a wide range of soils from poor sandy soils to heavy clayey alkaline and saline soils (more than 10 dS/m). This salt tolerance is particularly valuable in irrigated pastures where it can be cultivated without problem. Rhodes grass does better on fertile, well-structured soils and it prefers soil pH between 5.5 and 7.5. Establishment on acidic soils is difficult. It is tolerant of Li but not of Mn and Mg (Cook et al., 2005). Chloris gayana is a full sunlight species which does not grow well under shade (Ecocrop, 2014; FAO, 2014; Cook et al., 2005).

Forage management 

Establishment

Chloris gayana can be vegetatively propagated or established from seeds. For vegetative propagation, larger clumps can be cut into pieces and planted at 1 m distance from each other (NSWDPI, 2004). Because Rhodes grass seeds are fluffy, they may need to be coated or mixed with a carrier to improve the flow through the seeder (Moore, 2006). Seeds can be broadcasted or shallow-drilled (5-10 mm depth) during fall. The seeds can germinate under dry conditions provided that the soil has residual moisture (NSWDPI, 2004). The seeds establish readily on a well-prepared seed-bed. Mulching might help establishment after sowing. In Australia, aerial seeding is frequent (FAO, 2014Cook et al., 2005). As soon as favourable conditions occur in early spring, the grass resumes active growth and it provides full groundcover within 3 months of sowing (NSWDPI, 2004). The stand begins to produce valuable forage within 6 months, though the highest yield is obtained during the second year of cultivation (FAO, 2014Cook et al., 2005). In Australia, sowing Chloris gayana during late spring is done in order to kill weeds such as spiny burr grass (Cenchrus longispinus) (NSWDPI, 2004).

Associations

Chloris gayana can be sown alone or in combination with various other grasses such as Paspalum dilatatum, Setaria sphacelata, Cenchrus ciliaris or slower growing cultivars of Guinea grass (Megathyrsus maximus) (Cook et al., 2005). Chloris gayana can be mixed with oats or wheat that provide protection during winter, or it can be broadcasted in maize, sorghum or cotton crops (Duke, 1983). The association of Rhodes grass with a number of legumes has been shown to improve yields. These include alfalfa (Medicago sativa), stylo (Stylosanthes guianensis), perenial soybean (Neonotonia wightii), centro (Centrosema pubescens), phasey bean (Macroptilium lathyroides), Lotononis bainesiiDesmodium uncinatum and Trifolium sp. In Australia, it has been mixed with butterfly pea (Clitoria ternatea) for revegetation purpose (Cook et al., 2005).

Pasture and hay

Rhodes grass is suited to both rainfed and irrigated pastures. Stands require good management and added fertilizer (N) if long production (over 3 years) is intended, and the nutritive value of Rhodes grass can be improved through fertilizer or manure applications. The nutritive value peaks before bloom and then quickly declines. Grazing may maintain Chloris gayana in a leafy and highly nutritive condition provided grazing is not too heavy and practised over short periods. If the grass is used to make hay, cuttings can be done once a month (Göhl, 1982). During the first year of cultivation, livestock should not enter the stand until the secondary root system, which allows grass anchorage in the soil, is well established, otherwise the livestock might uproot the grass and damage the stand. In order to improve stand longevity through seedlings, newly established stands should be allowed to flower and set seeds before being grazed (FAO, 2014; Cook et al., 2005; NSWDPI, 2004).

Yield

Rhodes grass is a persistent, drought resistant and highly productive species. The highest recorded yield is about 30-40 t DM/ha while the average yield is in the 10-16 t DM/ha range (Ecocrop, 2014Murphy, 2010). 

Environmental impact 

Soil improver, soil revegetation and erosion control

Rhodes grass readily establishes and provides cover within 3 months of sowing (Moore, 2006). Using it as a cover crop improves soil structure, water infiltration and water-holding capacity, and its development lowers soil temperature during summer (Valenzuela et al., 2002). Its creeping habit provides good soil stabilisation and, in Australia, it is commonly used for the revegetation of mine-disturbed soils (Harwood et al., 1999). In Hawaii, Chloris gayana clippings were used to make mulch and protect soil from erosion. It could make a valuable seed bed for horticultural crops such as zucchini, cabbage, bulb onions, and eggplant, as it provides organic matter and protection from wind and sun to the vegetables (Valenzuela et al., 2002).

Weed potential and weed controller

Rhodes grass spreads readily in rainforest fringes in Queensland (Australia), where it produces seeds profusely and develops so quickly that it smothers native species and forms almost pure stands (DPIFQ, 2007). However, Chloris gayana was shown to outcompete summer weeds and has been considered helpful for controlling their development (Moore, 2006).

Nutritional aspects
Nutritional attributes 

Rhodes grass is a forage of highly variable composition. It can be a high quality forage when young (4 weeks of regrowth or less), with a protein content of over 15% DM (Mbwile et al., 1997a; Mero et al., 1997; Milford et al., 1968). However, the nutritional quality of Chloris gayana steeply declines with maturity: the crude protein decreases to 9-10% after 10 weeks of regrowth, and can be lower than 8% after 15 weeks (Milford et al., 1968), then Rhodes grass becomes protein-deficient for ruminants (Leng, 1990). The decrease in nutritive value is higher before the first cut compared to subsequent cuts, possibly because of the early flowering habit of the species (Mbwile et al., 1997b). Chloris gayana is characterized by the particularly low nutritive value of the stems compared to the leaves (Mbwile et al., 1997a; Mero et al., 1997; Milford et al., 1968). The nutritive value is also influenced by the season (Mbwile et al., 1997a) and variety (Mero et al., 1997; Milford et al., 1968).

The nutritive value of Rhodes grass assessed by NDF, protein and in vitro OM digestibility was found to be similar to that of the tropical grasses Cenchrus ciliaris, Bothriochloa insculpta and Panicum coloratum all sampled at the same stage of maturity (Mero et al., 1997). In a comparison of temperate and tropical forages, Chloris gayana was found to have an NDF content similar to that of Cenchrus ciliaris, but much higher than that of temperate forage species such as fescue, ryegrass, white clover and alfalfa. In particular, the stems and leaf sheaths of Rhodes grass and Cenchrus ciliaris contain a very high amount of NDF and lignin, and have a low in vitro digestibility compared to that of most temperate forages. It is likely that the tissue structure of the stems and leaf sheaths of both tropical grasses makes inner cells relatively inaccessible to the rumen micro-organisms (Wilman et al., 1998).

Rhodes grass is generally harvested for hay at a late stage of maturity, when the protein content is low, in the 5-8% DM range (Mtenga et al., 1990). Hay cut earlier (for example at 21 days regrowth) may have a protein content of about 15% DM, close to that of fresh grass (Tagari et al., 1977). Time of harvest and the sensitivity of variety to leaf shattering can have an important effect on the chemical composition of hay, and particularly on the crude protein content (Haffar et al., 1997).

Potential constraints 

Selenium accumulation

Rhodes grass is known to be a selenium accumulator, and, when grown on selenium-rich soils, its selenium content can cause mortality or morbidity in livestock (NSWDPI, 2004). Acute toxicity occurs at 3 mg of selenium per kg BW in cattle and causes death within a few days after intoxication, with no known treatment. However, seleniferous plants are not readily eaten by most animals due to their bitter taste and strong odour, and tend to be consumed only when other forage is sparse (Cornell University, 2014).

Ruminants 

Rhodes grass can be a high quality forage for ruminants when grazed or harvested at an early stage of maturity. However, its nutritive value strongly decreases with maturity, especially after the first cut. Hay harvested at a later stage of maturity has a low protein content and a high fibre content, particularly in the stems, and it should be supplemented when fed to ruminants with nutritional requirements higher than those necessary for maintenance.

Digestibility

Young Rhodes grass of 4 weeks of regrowth or less was found to have a high in vitro OM digestibility of 70-80 % (Mbwile et al., 1997aMero et al., 1997), which decreased to 50% after 10 weeks of regrowth (Mero et al., 1997). In Kenya and Tanzania, in vivo OM digestibility and intake of Rhodes grass by dairy cows or heifers decreased with increasing maturity after the first cut (Abate et al., 1981Mbwile et al., 1997b). In Tanzania, in vivo OM digestibility decreased from 76% at 6 weeks of regrowth to 60% at 12 weeks of regrowth in cows fed fresh Rhodes grass (Mbwile et al., 1997b). In Kenya, intake of Rhodes grass decreased with maturity in grazing growing Friesian and Ayshire heifers (Abate et al., 1981). However, after the second cut, the effect of the stage of maturity on intake and in vivo digestibility was less important as these parameters remained high even with mature forage (Mbwile et al., 1997b). OM digestibility in grazing heifers was higher during the wet season than during the dry season (Abate et al., 1981).

Pasture and fresh forage

In Australia, Chloris gayana fed at a late stage of maturity was fed to lactating cows of moderate yield, generally with supplementation. Dairy cows grazing irrigated Rhodes grass pasture (2 to 6 weeks regrowth, after the 2nd or 3rd cut) mulched at least once a year produced more than 14.3 kg/d of milk when supplemented with 5 kg of cereal-based concentrate per cow at a stocking rate up to 3.7 cows/ha (Ehrlich et al., 2003a). In a follow-up study, with Holstein-Friesian dairy cows grazing irrigated Rhodes grass pastures (6-week grazing rotation), supplemented with 5 kg of cereal-based concentrate, increasing the stocking rate from 3.5 to 6.1 cows/ha had no effect on milk production. However, cows stocked at stocking rates higher than 3.5 cows/ha could not maintain live-weight during the 18-week experiment, and it was recommended to increase the level of supplementation for high stocking rates (Ehrlich et al., 2003b).

In Tanzania, lactating Friesian cows were fed with fresh Rhodes grass that was supplemented only with a small amount of salts. However, the evolution of milk production during the experiment was not reported, although the cows produced 8.7 kg milk/d at the beginning of the experiment (Mbwile et al., 1997b). In Kenya, dairy heifers grazing Rhodes grass had an average daily gain of 581 g/day during a one year experiment with a stocking rate of 2 livestock unit/ha, but the pattern of gain ranged between 200 and 1100 g/d according to the period of the year. Supplementation, when forage is of low quality, was recommended in order to sustain an average daily gain of 550 g/d (Abate et al., 1981).

Cows not only prefer to eat leaves rather than stems but have the ability to select leaves over stems in Rhodes grass (Mbwile et al., 1997b; Ehrlich et al., 2003a). In order to maximize intake, it can be useful to allow a high level of selection of forage by cows, by offering 10 to 20% excess feed depending on the maturity and cut (Mbwile et al., 1997b).

Hay

In order to optimize the harvested biomass, Rhodes grass hay is generally harvested at an advanced maturity stage. However, hay alone is unlikely to meet the nutritional requirements of productive ruminants and must, therefore, be supplemented (Mero et al., 1998Mtenga et al., 1990; Mupangwa et al., 2000; Osuga et al., 2012). Rhodes grass hay cut early (21 days of regrowth) had a high nutritive value, comparable to that of fresh Rhodes grass (Tagari et al., 1977).

A first limitation of the nutritive value of mature Chloris gayana hay is its low intake by livestock when compared to hays of other tropical grass species. In Tanzania, in Blackhead Persian rams, the intake of Rhodes grass hay harvested at 6 or 10 weeks of regrowth was 20% lower than that of Cenchrus ciliaris and Panicum coloratum, even though the in vivo OM digestibility of the hays were comparable. It was recommended to allow for 30 to 50% of refusals, depending on maturity, so that the animals could select the most digestible parts. Rhodes grass hay was then able to meet sheep maintenance requirements (x 1.1-1.2) (Mero et al., 1998).

Another limitation of mature Rhodes grass hay is its low protein content, particularly during the dry season. Several trials have shown that supplementation with a protein-rich source resulted in higher animal performance (Mtenga et al., 1990Mupangwa et al., 2000Osuga et al., 2012). In Tanzania, goats fed a low protein Chloris gayana hay (5.7-7.7 % DM) were supplemented with concentrates containing between 10-18% DM protein. The supplement increased total feed intake, doubled the growth rate, and improved the feed conversion ratio and the lean + fat:bone ratio (Mtenga et al., 1990). In Zimbabwe, with East African goats, supplementation of a low protein Rhodes grass hay (7% DM) with 100 g/d of maize grain and 25% of legumes (Cassia rotundifolia, Lablab purpureus or Macroptilium atropurpureum, 12% DM of protein) increased daily gain, total intake and the supply of microbial nitrogen for absorption in the lower intestinal tract (Mupangwa et al., 2000). In Kenya, with growing East African goats, supplementation of a poor quality Chloris gayana hay (5% DM protein) with 60 g of maize bran and 15 or 30 % of legumes (Berchemia discolor or Ziziphus mucronata) increased intake, multiplied live-weight gain per 6 to 12 and increased the ammonia content of the rumen above 50 mg/l (Osuga et al., 2012), which is considered as the minimal concentration required to maximize microbial growth in the rumen (Leng, 1990).

Silage

Ensiling of Rhodes grass has been little studied, since it is difficult to ensile due to its high moisture coupled with low contents of water-soluble carbohydrates, similar to other tropical grasses (Parvin et al., 2010). In Australia, with Friesian-Holstein heifers, a comparison of Rhodes grass cut at two stages of maturity (60 and 100 days) and treated with CaO, NaOH or a microbial inoculant before ensiling found that only NaOH treatment allowed a 25% increase of DM intake for mature grass silage and increased its in sacco digestibility. It also reduced NDF content. None of the treatments had positive effects on the in vivo nutritive value or storage quality of young Chloris gayana silage (Chaudhry et al., 2001).

Rabbits 

Rhodes grass as fresh forage or hay can be safely used in rabbit feeding but only as a fibre source, as shown by the following trials. In Mauritius, Chloris gayana gave the lowest growth rate in a comparison of 7 forages offered to growing rabbits as fresh forage in addition to a limited quantity of concentrate (Ramchurn, 1979). In Nigeria, when Rhodes grass hay and a concentrate were offered ad libitum, the forage represented 1/3 of the daily DM intake, but this proportion was reduced to 20% when another forage was added in a 3-feed choice design (Iyeghe-Erakpotobor et al., 2006). When offered as the only feed, Chloris gayana did not meet the maintenance requirements of rabbits, due to its poor energy digestibility (36%), low protein content (8% DM) and low protein digestibility (32%) (Raharjo et al., 1986). In Kenya, a comparison of Rhodes grass, sweet potato vines and dried maize leaves showed that Rhodes grass gave the lowest growth rate, particularly when the concentrate was limited (Mutetikka et al., 1990).

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 24.9 6.2 16.7 39.0 197  
Crude protein % DM 9.0 2.8 5.1 15.7 262  
Crude fibre % DM 36.9 3.9 28.2 43.4 235  
NDF % DM 75.0 3.4 69.9 82.1 28  
ADF % DM 43.0 3.3 36.6 47.1 22 *
Lignin % DM 6.0 1.7 2.7 7.7 12 *
Ether extract % DM 2.2 0.5 1.2 3.4 179  
Ash % DM 9.0 1.7 6.1 13.2 256  
Gross energy MJ/kg DM 18.3         *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 3.8 1.0 2.2 5.9 197  
Phosphorus g/kg DM 2.9 0.9 1.3 5.3 201  
Potassium g/kg DM 18.7 5.6 7.7 29.4 187  
Sodium g/kg DM 3.1 1.5 0.2 5.6 16  
Magnesium g/kg DM 1.9 0.5 1.0 2.9 171  
Manganese mg/kg DM 72 65 18 268 31  
Zinc mg/kg DM 28 12 16 65 31  
Copper mg/kg DM 6 1 4 9 31  
Iron mg/kg DM 237 180 97 498 4  
               
Ruminant nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 60.4 7.5 52.0 78.5 18 *
Energy digestibility, ruminants % 57.7         *
DE ruminants MJ/kg DM 10.6         *
ME ruminants MJ/kg DM 8.5         *
Nitrogen digestibility, ruminants % 65.3 7.7 45.0 76.2 21  

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

References

Aumont et al., 1991; Bwire et al., 2003; CIRAD, 1991; Dzowela et al., 1990; French, 1943; Hassan et al., 1979; Hassoun, 2009; Holm, 1971; Mbwile et al., 1997; Mlay et al., 2006; Shem et al., 1999; Singh et al., 1992; Tagari et al., 1977; Todd, 1956; Todd, 1956; Todd, 1956; Walker, 1975; Work, 1937

Last updated on 14/10/2014 16:37:02

Main analysis Unit Avg SD Min Max Nb  
Dry matter % as fed 86.4 3.5 76.2 92.8 141  
Crude protein % DM 10.1 3.0 4.4 16.6 193  
Crude fibre % DM 35.3 2.1 31.2 40.4 131  
NDF % DM 75.7 2.9 70.5 80.8 30  
ADF % DM 41.2 3.8 37.0 50.1 35 *
Lignin % DM 5.6 1.0 3.8 7.7 28 *
Ether extract % DM 1.7 0.5 0.9 2.5 31  
Ash % DM 9.7 1.5 6.7 13.2 148  
Gross energy MJ/kg DM 18.1 0.3 18.1 19.8 7 *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 3.1 0.7 2.0 4.6 66  
Phosphorus g/kg DM 2.6 0.6 1.6 4.2 67  
Potassium g/kg DM 16.9 5.3 5.0 23.8 54  
Sodium g/kg DM 4.1 3.0 1.2 8.9 13  
Magnesium g/kg DM 1.4 0.3 0.9 2.2 54  
Manganese mg/kg DM 107 46 47 209 9  
Zinc mg/kg DM 22 19 0 83 17  
Copper mg/kg DM 5 2 3 9 17  
Iron mg/kg DM 31 83 0 220 7  
               
Ruminant nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 59.0 5.1 50.1 68.7 55 *
Energy digestibility, ruminants % 55.6         *
DE ruminants MJ/kg DM 10.0         *
ME ruminants MJ/kg DM 8.1         *
Nitrogen digestibility, ruminants % 40.5 13.3 17.0 55.0 14  

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

References

CIRAD, 1991; El-Hag et al., 1992; French, 1943; Gartner et al., 1975; Hassoun, 2009; Holm, 1971; Holm, 1971; Kategile et al., 1988; Kennedy et al., 1992; Mahgoub et al., 2005; Mandibaya et al., 1999; Milford et al., 1968; Minson, 1971; Mtenga et al., 1990; Mupangwa et al., 2000; Ondiek et al., 1999; Osuga et al., 2012; Rees et al., 1980; Richard et al., 1989; Shem et al., 1999; Todd, 1956

Last updated on 14/10/2014 16:33:51

Main analysis Unit Avg SD Min Max Nb  
Dry matter % as fed 21.8 1.3 20.1 23.6 5  
Crude protein % DM 10.1 4.1 4.5 16.1 5  
Crude fibre % DM 33.8 4.5 26.8 37.2 5  
NDF % DM 69.1         *
ADF % DM 39.6         *
Lignin % DM 5.3         *
Ether extract % DM 2.2       1  
Ash % DM 13.8 1.6 12.8 16.6 5  
Gross energy MJ/kg DM 17.4         *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 4.6       1  
Phosphorus g/kg DM 3.3       1  
Potassium g/kg DM 34.0       1  
Magnesium g/kg DM 3.7       1  
               
Ruminant nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 62.7         *
Energy digestibility, ruminants % 58.6         *
DE ruminants MJ/kg DM 10.2         *
ME ruminants MJ/kg DM 8.2         *
Nitrogen digestibility, ruminants % 8.9       1  

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

References

Blair Ralns, 1963; CIRAD, 1991; Hassoun, 2009

Last updated on 14/10/2014 16:35:03

References
References 
Datasheet citation 

Heuzé V., Tran G., Boudon A., Lebas F., 2016. Rhodes grass (Chloris gayana). Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. http://www.feedipedia.org/node/480 Last updated on January 12, 2016, 15:21

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