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Feedipedia

Sorghum forage

Datasheet

Description
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Common names 

Sorghum, broomcorn, forage sorghum, grain sorghum, milo, great millet, durra, dourah [English]; sorgho, sorgho grain, sorgho fourrager, gros mil [French]; Mohrenhirse, Durrakorn, Besenkorn, Guineakorn [German]; sorgo, milho-zaburro [Portuguese]; sorgo, zahína [Spanish]; kafferkoren [Dutch]; sorgo, saggina [Italian]; ذرة بيضاء ; ورغم [Arabic]; জোয়ার [Bengali]; 高粱 [Chinese]; ज्वार (jwaarie, jowar, jowari) [Hindi]; モロコシ [Japanese]; 수수속 [Korean]; сорго [Russian]; ข้าวฟ่าง [Thai]

  • Forage sorghum, sorghum silage, sorghum hay, sorghum straw, sorghum stover, sorghum stubble
Synonyms 

Sorghum vulgare Pers. There are numerous synonyms for Sorghum bicolor (see GRIN for an exhaustive list).

Description 

Sorghum (Sorghum bicolor (L.) Moench) is used for both grain and forage. While some varieties are grown solely for grain, others have been developed for forage production, and some varieties are dual purpose (Harada et al., 2000). The sorghum plant is a tall, erect annual grass, up to 5 m high, and follows the C4 pathway. Sorghum roots are adventitious and the root system can extend from the top 90 cm soil layer to twice that depth. Culms are erect, solid, 0.6 to 5 m high and 5 to 30 mm diameter. Leaves are broad, glabrous, very similar to maize leaves but shorter and broader. Inflorescence is a panicle, around 60 cm long, bearing up to 6000 spikelets (Balole et al., 2006). Sorghum bicolor is highly variable. The stem is the part of the plant that shows the greatest differences between genotypes, ranging from thin to thick, with low or multiple tillering (Rattunde et al., 2001).

Sorghums used for forage fall in four categories (Suttie, 2000):

  • Grain sorghums. Dual purpose varieties can be directly used as fodder, or livestock can eat the straws or stubble from all varieties after the grain has been harvested. Many sorghums used for forage in the tropics belong to the tall (2 to 4 m), thick-stemmed landrace types and are used as dual purpose (grain and forage) crops (Magness et al., 1971).
  • Sweet sorghums. Their stems contain a sweet juice used on a small scale for sugar making. They are grown as fodders, especially in the USA, and are used in the development of fodder hybrids. In more intensive production, fodder cultivars are usually crosses between grain and sugar sorghums. These have a higher sugar content than ordinary sorghums and are less liable to cause HCN poisoning. They can also be used for silage or hay (Suttie, 2000).
  • Sudan grass (Sorghum × drummondii) and Columbus grass (Sorghum × almum). These species are described in their respective datasheets.
  • Commercial hybrid fodder sorghums, usually based on Sudan grass and grain sorghum. They retain the multi-cut qualities of Sudan grass but have a much higher yield potential. They are becoming popular for green fodder in some developing countries and seeds are internationally available.

The germplasm of sorghum is extensive. For instance, the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in Patancheru, India, keeps a collection of 36,000 accessions from all the major sorghum-growing regions of the world (Balole et al., 2006). This datasheet is about Sorghum bicolor forage but will occasionally concern sorghum hybrids.

The brown midrib sorghums (bmr), which have been specifically developed for forage, are particularly notable. The stems and leaves of bmr phenotypes are less lignified, resulting in higher cell wall digestibility (Barrière et al., 2003; Ouda et al., 2005; Contreras-Govea et al., 2010; Pedersen et al., 2000). Unfortunately, the bmr trait is associated negatively with plant health, survival, environmental fitness and biomass yield, which tends to limit the adoption of bmr varieties by farmers (Contreras-Govea et al., 2010). In dual purpose sorghums, the nutritive value of the forage has seldom been taken into account in the past. However, cultivars that have both an enhanced grain yield and a higher forage value are now being developed, notably in India (CGIAR, 2010).

Forage sorghum is a valuable fodder: it is relished by ruminants, it is outstandingly drought resistant and it grows where maize is not able to grow because of high temperatures or dry conditions. Forage sorghum can be grazed (young or as deferred fodder), cut fresh, made into hay or ensiled (Pedersen et al., 2000).

Distribution 

Sorghum is native to East Africa, probably from Ethiopia (Ecoport, 2011), but was also grown in India before recorded history and in Assyria as early as 700 BC. It was introduced to the USA from Africa in the early part of the 17th century (Undersander et al., 2003; Balole et al., 2006). It is now widespread between 50°N (USA and Russia) and 40°S, and from sea level up to an altitude of 1000 m (Ecoport, 2011). Optimal growth conditions for sorghum are 25-30°C at seedling and 30°C day-temperature during growth, with less than 400-750 mm annual rainfall. It grows best on deep, well-drained loamy clay with a pH between 5.5 and 7.5.

Sorghum is tolerant to drought because of its root system. It performs better than maize in drought conditions and thus grows in stress-prone semi-arid areas unsuitable for maize (FAO, 2011). The level of salt-tolerance depends on the variety. An accumulation of salt may inhibit germination. Sweet sorghum is highly salt-tolerant once well-established (Cook et al., 2005) and in some areas sorghum has been described as one of the most salt-tolerant grass species (Fahmy et al., 2010). Sorghum is somewhat tolerant to waterlogging (during short periods). It is sensitive to frost and to sustained flooding. It is also susceptible to weeds during the first stages of development. In Africa, Striga hermonthica, a parasitic weed, attaches itself to the roots and is particularly noxious to sorghum (FAO, 2011).

Forage management 

Note: the forage management practices reported below are mostly derived from North American and Western European guidelines concerning sweet sorghums and commercial Sudan x sorghum hybrids. They may not be suitable for forage sorghums grown in tropical and/or developing countries. Given the variability of the sorghum germplasm, the intensive breeding efforts and the large number of ecological and farming systems where forage sorghums are grown, precise recommendations and values for yields, optimal heights, etc. will eventually depend on local conditions and varieties.

Yields

Forage sorghums yield annually about 20 t green matter/ha (Balole et al., 2006) but may reach 75 t/ha under optimal growth conditions (FAO, 2011).

Pasture

Forage sorghum can stand heavy grazing. Rotational grazing is the safest way of utilizing the pasture to provide maximum nutrition. There is a relatively short window for optimal grazing of sorghum. It should not be grazed below 15 cm if good regrowth is expected. Because new shoots can be dangerous due to hydrogen cyanide, they should not be grazed until they reach at least 45 cm (Undersander et al., 2003) or even 0.8-1 m (Vignau-Loustau et al., 2008). The optimal height for grazing is 1-1.5 m. At heading, both nutritive value and palatability start decreasing rapidly. Livestock then graze the plant selectively and trampling occurs if the plants are too tall (Undersander et al., 2003; Vignau-Loustau et al., 2008).

There is increased danger of HCN poisoning when frost kills the top-growth, leaving the base of the plant from which new and palatable shoots may emerge. Cattle will frequently avoid the tall frosted growth and graze the young shoots, which may contain toxic levels of HCN. Harvesting the crop for silage may be the best way to handle frost-damaged sorghums (Undersander et al., 2003).

Green chop

Sorghum green chop can help to bolster summer feed supplies. Freshly cut sorghum should be consumed rapidly to prevent the formation of HCN (Undersander et al., 2003).

Hay

Sorghum hay should be chaffed before giving to livestock to avoid wastage (Suttie, 2000). To obtain the highest yield, hybrid sorghum should be harvested for hay when the seeds are between the soft and dough stage, but curing is difficult at this time. Harvesting when the forage is about 80 cm high results in a better quality hay that is easier to cure, and one or two additional crops may be produced (Undersander et al., 2003).

Silage

With hybrid sorghums, the best stage for ensiling sorghum is the medium dough stage (plant moisture: 65-70%). For beef cattle, the crop can be harvested a few days later (Undersander et al., 2003). Grain sorghum should be ensiled when the top seeds are in the dough stage and the bottom ones in the milky stage (Vignau-Loustau et al., 2008). Sweet sorghum used for silage should be cut before the seeds mature; otherwise a large portion of the small hard seeds will be wasted as they are not easily digested (Göhl, 1982).

Forage sorghum silage ferments similarly to maize, with a pH below 4.0 (Filya, 2003; Contreras-Govea et al., 2010). In Brazil, sorghum silage reached the threshold pH of 3.9 (required to prevent the development of lactic acid bacteria) after 7 days and was found to be stable between 2 and 4 weeks (Rodriguez et al., 1999). Because forage sorghum is sometimes ensiled with a higher moisture content than maize, greater acetic acid concentration can be expected (Contreras-Govea et al., 2010).

Environmental impact 

Water efficiency and salt-tolerance

Sorghums have a high water efficiency, requiring less total water to reach their production potential than maize. In environments where water is limited due to drought or declining aquifers, and where it is necessary to conserve or reallocate available water, forage sorghums are promoted as a substitute for more water-consuming crops, particularly forage maize. Sorghums will be an extremely valuable forage wherever water becomes a scarce and precious resource due to global climate change (Brouk et al., 2011; Emile et al., 2006; Contreras-Govea et al., 2010). The combination of drought-tolerance and salt-tolerance makes sorghum a very interesting feed resource under arid and semi-arid conditions in saline lands (Al-Khalasi et al., 2010; Fahmy et al., 2010; Khanum et al., 2010).

Toxic soil reclamation

Sorghum is tolerant of many pollutants and it thrives in toxic soils that kill most plants. Sorghum can take up excess soil N due to its penetrating root system and this ability has been useful to reclaim fallow lands where soil N up to 400 kg/ha has been recorded. Sorghum also thrives on salty irrigated soils: it restores the porosity of the soil making it possible to grow a high yielding wheat crop in one season (NRC, 1996).

Cover crop and soil improver

Sorghum can be used as a cover crop during the fall and winter: sown during the fall, it covers more than 60% of the soil surface before winter and protects it from wind erosion. It also helps sparing more water than other cover crops because it dies quickly after the first frost and does not withdraw water from the soil. After harvest, ploughing down the stubbles can improve the organic status of the soil and limit erosion (UC SAREP, 2006; NRC, 1996).

Weed and pest control

Detrimental effects on broad-leaf weeds last beyond the life of the sorghum. This could be due to the release of phenolics and cyanogenics by the roots (NRC, 1996).

Crop support

Dead stalks of sorghum grain can provide support to climbing legumes several months after the grain is harvested (NRC, 1996).

Regeneration of native pastures

In Queensland, Australia, sweet sorghum was one of the species successfully used in attempts to revegetate severely degraded bluegrass pastures (Dichanthium sericeum). It was added to the mixture to give extra competition to volunteer weeds and as a safety measure to ensure cattle had fodder in the paddock. It provided fodder four to five months after sowing and cattle preferred it to the other sown species (Lambert et al., 1999).

Nutritional aspects
Nutritional attributes 

The composition of sorghum forage depends on its stage of maturity, variety, climate, harvest conditions and many other factors. As in most forages, protein content and, more generally, nutritive value, declines with maturity. In whole-crop forage sorghums grown in Western Europe, protein content started at the high level of 19.0% DM at bolting, dropping to 12.9% DM one week before early heading, and 6.9% DM at the milk stage. The ADF content started at 31.2% DM, rose up to 37.4% DM at heading and slightly decreased to 35.4% DM at the milk stage (INRA, 2007).

In whole-crop silages, protein content is about 10-11% DM and starch content varies from 22-28% DM at the milk stage to 30-32% at the hard dough stage (Vignau-Loustau et al., 2008). However, values obtained in tropical sorghums may be different. In Brazil, for example, crude protein decreased exponentially from about 14% at 40-50 days of age and stabilized at 3-5% DM (Pizarro et al., 1984).

Sorghum is a close relative to maize and shares the same photosynthetic pathway (C4), but there are differences in tissue structure and distribution (stems, leaves, ears) between both plants. Comparisons of maize and sorghum plants in the USA have shown that the proportion of leaves and ears was greater and stem was lower in maize than in forage sorghum, at all stages of maturity. As a result, fibre content is higher in sorghums than in maize, 35% DM vs. 29% in a comparison of maize hybrids and sorghum cultivars harvested for silage, which resulted in a generally lower nutritional value for sorghum. While ADF concentration in the leaves increased with maturity (from 34.6% DM at the milk stage to 40.3% at the hard dough stage), it remained relatively constant in the stems (38-39% DM) or tended to decrease (Contreras-Govea et al., 2010). Leaves are also richer in protein than the stems (13.6 vs. 8.3% DM for Sorghum bicolor and similar values were reported for a Sudan grass x Sorghum bicolor hybrid in Egypt; Gabra et al., 1985).

Breeding programmes, and notably the development of low-lignin, higher-digestibility bmr sorghums, are trying to narrow the gap between forage sorghum and forage maize (Contreras-Govea et al., 2010). In a four-year review of 270 sorghum forage accessions (including 99 bmr sorghums), it was found that NDF and ADF did not differ significantly between bmr and non-bmr varieties. The ADL in bmr varieties was 23% lower (average of 4.3% DM) than in non-bmr varieties. In vitro DM digestibility of bmr varieties was only slightly superior to that of non-bmr varieties. Some conventional forage sorghum cultivars had a similar or greater nutritive value than some bmr forage sorghums. In somes cases, however, in vitro digestibility of bmr varieties were within the same range, similar to, or higher than the average for maize silage. It was concluded that the bmr label on a variety did not guarantee superior digestibility and nutritional value and that choosing a forage sorghum cultivar should be based on its individual performance rather than on the bmr type alone (McCollum et al., 2005). These conclusions were confirmed by other researchers (Contreras-Govea et al., 2010).

Potential constraints 

Sorghum contains hydrogen cyanide and nitrates/nitrites, which may be toxic for animals if they are ingested at a high level. There are varietal differences between sorghum strains (Luthra et al., 1976).

Hydrogen cyanide

Dhurrin, a cyanoglycoside, is present in the aerial parts of most sorghum varieties. It is particularly concentrated in the young leaves and tillers and in plants that are suffering from drought. Dhurrin is hydrolysed into hydrogen cyanide in disrupted plant tissues or in the rumen of animals that consume the forage. HCN is highly toxic and can kill grazing animals. Forage sorghum can potentially contain between 100 and 800 mg HCN/kg plant DM. It is lethal to ruminants if consumed at 2 mg/kg body weight. Symptoms of acute HCN poisoning in ruminants are excitement, difficult breathing, muscle tremors, staggering, convulsions, collapse and death, which can occur in less than 15 minutes but generally within 1 or 2 hours. A chronic form of HCN poisoning also exists that results in sulphur deficiencies in ruminants (Pedersen et al., 2000).

In the plant, HCN levels usually decline with age, reaching non-toxic levels 45-50 days after planting (Hanna et al., 2001). The HCN is partly destroyed when the fodder is made into hay or silage, where it degrades in 2 or 3 weeks after ensiling (Undersander et al., 2003). Low HCN potential varieties of sorghum have been developed (Hanna et al., 2001).

Nitrates and nitrites

Sorghum is a nitrate accumulator and, while nitrates are generally non-toxic to ruminants, their transformation into ammonia, within the rumen, produces toxic nitrites. Nitrites bind with haemoglobin to form methemoglobin, preventing blood from binding with oxygen, resulting in oxygen starvation of the tissues, accompanied by increased pulse and respiration rates, and animal death in the most severe cases (Marais, 2001; Fahmy et al., 2010).

Nitrate levels ranging from 0.5 to 1% DM in the plant are considered potentially toxic to ruminants. Nitrate levels higher than 1% DM are considered dangerous (Yaremcio, 1991). Nitrates are more concentrated in the stems than in the leaves (Aii, 1975; Harada et al., 2000).

Several environmental conditions result in nitrate accumulation, notably severe drought, high applications of N fertilizer and killing frost (Pedersen et al., 2000). A well-managed programme of N fertilizer application can reduce nitrate accumulation (Wilmoth et al., 2000).

To prevent nitrate poisoning, livestock should not be given full access to forage sorghum: in strip grazing at high stocking rates, livestock only choose the leaves that have less nitrates than the stem. The sward should not be grazed immediately after plant stress and should be allowed to mature, as this decreases its nitrate content. Ensiling may also be a way of reducing nitrate levels (by 40 to 60%). If nitrate accumulation is suspected, the herd should be fed with other feeds prior to entering the stand so that nitrates are diluted in the ration (Pedersen et al., 2000).

Ruminants 

Sorghum forage can be used in different ways, as pasture, green chop, hay, silage and crop residues (straw, stubble and leaves). Due to its relatively low protein content, it usually requires protein supplementation as well as minerals and vitamins (Undersander et al., 2003). The bmr varieties, developed since the 1990s, are supposed to have a higher fibre digestibility, making them competitive with maize (Brouk et al., 2011).

Due to the vastness of the topic, the following recommendations for ruminants do not constitute an exhaustive overview of the utilization of sorghum forage throughout the world. They represent a sampling of reported scientific work on the subject. Readers are invited to consult their local extension services for specific advice on the best way to use sorghum forage in their specific circumstances.

Intake

For forage sorghums grown in Western Europe, intake is good at the beginning of the growth cycle but decreases rapidly as soon as the inflorescence grows. Intake is higher for regrowth: for instance, intake at bolting stage in the 1st cycle is 21.5 g DM/kg LW while intake at regrowth is 24.0 g DM/kg LW (Vignau-Loustau et al., 2008).

Digestibility and energy value

As an example of the variation in the nutritive value, OM digestibility and ME values for fresh whole sorghum grown in Western Europe were 71% and 9.5 MJ/kg DM at bolting, decreasing to 61% and 8.4 MJ/kg DM at heading, and more or less stabilising after that stage. The differences between an eight-week regrowth grown in normal conditions or during a drought were -12 percentage points for OM digestibility (70 to 58%) and -1.4 MJ/kg (9.4 to 8 MJ/kg DM) (INRA, 2007).

When compared to maize silage, sorghum silage is more fibrous and less digestible. In temperate regions, whole crop sorghum silage has a nutritive value higher than that of fodder grasses and legume silages, and close to that of a medium-quality maize silage (Vignau-Loustau et al., 2008). It has been noted that equations based solely on ADF for predicting digestibility are likely to underestimate the value of bmr varieties (Brouk et al., 2011).

Pasture and stubble

While silage is the main use of forage sorghum (notably in temperate and developed countries), pasture and stubble grazing are common practices in some areas. In Australia, for instance, fodder sorghums are also used for autumn grazing by dairy and beef cattle to fill in a period of feed shortage between summer and winter grazing crops. The grain sorghums are valuable for grazing after the grain has been harvested and the crop residues (stubble, dropped seed-heads and regrowth, plus weeds) provide good autumn and winter roughage (Cook et al., 2005).

Dairy cows

In Venezuela, cows grazing ad libitum a mixture of Sorghum bicolor and Pennisetum purpureum with a concentrate supplement produced on average 17.0 kg of 4% fat-corrected milk during the first 6 months from 2nd and 3rd lactation cows (Bodisco et al., 1976).

Beef cattle

In Queensland, Australia, yearling steers grazing sweet sorghum at the rate of 1.25 head/ha had an average daily gain of 0.86 kg/head/d over 7 months (experiment from 1965 cited by Cook et al., 2005).

Several trials have taken place in Brazil demonstrating that sorghum pastures can support growth although being slightly inferior to other grasses. Thirteen-month old Charolais, Nelore and crossbred steers (1.75 t/ha) grazing fertilized sorghum pasture gained around 50 kg in 3 months (0.61 kg/head/d) (Neumann et al., 2005). Fifteen-month old crossbred heifers gained less weight grazing sorghum than Pennisetum americanum (0.71 vs. 0.78 kg/head/d) (Coser et al., 1983). In a comparison of several grasses, including Sorghum bicolor, Pennisetum purpureum, Brachiaria plantaginea and Pennisetum americanum, steers grazing sorghum had the second best daily gain (1.121 kg/d) after Pennisetum americanum, but no significant differences were found in terms of stocking rate and live-weight gain. It was concluded that a properly managed summer sorghum pasture could be used as an alternative source of feed in intensive beef cattle production systems (Restle et al., 2002).

Green chop

Fresh sorghum forage is highly palatable to goats but they prefer it chopped (Abdel-Moneim et al., 1999). In Sudan, a comparison of cut-and-carry alfalfa and sorghum forages fed to sheep and cattle found that alfalfa intake was higher than sorghum intake. Dry matter digestibility of alfalfa and sorghum was similar in cattle but alfalfa was more digestible in sheep. Supplementation with sorghum grain and molasses increased the digestibility of sorghum forage in both species (Ahmed et al., 1983).

Hay

Sheep

Because of its salt-tolerance, sorghum forage can be valuable in saline soils, for example in coastal areas and other salt-affected regions of North Africa and the Middle-East. In Oman, sorghum hay grown under levels of high salinity (3, 6 and 9 dS/m) may be used for feeding Omani sheep without adverse effects on health or performance. Sheep ate similar quantities of sorghum and Rhodes grass (Chloris gayana) hay, but their daily weight gain tended to be lower with sorghum. Dry matter and crude protein digestibilities were lower with sorghum than with Rhodes grass, but fibre digestibilities were similar (Al-Khalasi et al., 2010).

In Egypt, sorghum grass cultivated in strongly saline soils (10 dS/m), and irrigated with water containing 4000 to 7000 ppm total salts, contained enough nutrients to cover the nutritional requirements of sheep. Yields were also promising, indicating that sorghum forage could have the potential to solve summer and autumn feed shortages and increase the economic value of marginal saline resources (Fahmy et al., 2010). In Pakistan, sorghum hay (regular and bmr varieties) cultivated in saline land and harvested 80 days after sowing could profitably replace wheat straw as the basal fodder for sheep. Regular sorghum was almost twice as productive as bmr sorghum (13.2 vs. 7.5 t/ha) (Khanum et al., 2010).

Goats

In a trial with dairy goats, sorghum hay replaced alfalfa hay without impairing milk yield (Andrade et al., 1996). No differences in digestibility of medium quality sorghum hay and high quality oat hay forages fed to Rambouillet sheep and Angora goats were observed. However, Angora goats, who have higher protein requirements to facilitate growth of mohair, responded to higher levels of supplementary protein by increasing their intake (Huston et al., 1988).

Silage

Most trials with sorghum silage have taken place in developed and temperate countries and have examined the merits of sorghum relatively to maize for dairy cows.

Dairy cows

Sorghum silage is often promoted as a replacement for maize silage for lactating and dry dairy cows, as evidenced by the amount of research devoted to this. The conclusion so far is that utilization of sorghum forage as a total replacement for maize silage in the diets of lactating cows is possible in some cases. Studies have reported similar milk production from sorghum silages, and particularly bmr sorghums, as from maize silage. In France, an example of  successful utilization of sorghum (from a non-bmr cultivar) has been described as follows: in a 15-week trial, dairy cows were fed sorghum or maize silage ad libitum with 2.2 kg/d of concentrate (and 50 g/d of urea for the maize treatment). The sorghum silage was more palatable than maize silage (+ 15% DM intake), milk production was similar (about 20 kg/d) and fat content was higher with the sorghum treatment (4.26 vs. 4.01%). However, the authors noted that, in a previous trial, grains were not properly fertilized because of drought, causing bad silage quality and a milk yield much lower (-16%) than for the control diet (Emile et al., 2005). In the USA, when cows were fed 65% silage (maize, alfalfa, bmr and regular sorghum), the bmr sorghum silage resulted in a milk yield lower than that from maize silage, similar to that obtained with alfalfa and higher to that obtained with regular sorghum. In a second experiment, bmr silage fed at 35% of the diet resulted again in a higher yield than regular sorghum silage, and equal yield to that from maize silage (Aydin et al., 1999). However, there are large differences in nutrient profiles between varieties, together with agronomic and climatic variation, which can affect yield, therefore total substitution of maize silage with sorghum silage, even from bmr varieties, should be given careful consideration (McCollum et al., 2005; Brouk et al., 2011).

Growing and beef cattle

The use of sorghum silage in beef cattle has been much less investigated than in dairy cattle. It is used by commercial farms in the USA where it is considered to offer better control of weight gain in growing and dry cattle (Brouk et al., 2011). In a two-year trial in Texas, bmr sorghum silage was tested in finishing diets, based on steam-flaked maize, and was fed either at 10% (diet DM), substituting totally for maize silage, or at 7.5% to contribute the same amount of NDF as maize. There were no differences in feed intake, daily gain, feed efficiency, or carcass traits among the treatments (McCollum et al., 2005).

Sheep

In sheep fed sorghum silage in Brazil, the optimum level of concentrate (maize grain, soybean meal and wheat bran) in the diet was between 30 and 45%. This amount increased the availability of DM in the forage, and the nutritional value of the diet, promoting animal productivity (Simon et al., 2008).

Straw and stover

Sorghum straws have a poor nutritive value with an OM digestibility lower than 50% and animals must be supplemented with protein-rich concentrates (Blümmel et al., 2003). In Nigeria, the best levels of supplementation for cottonseed cake supplementation were respectively 60 g/d for sheep and 48 g/d for goats. Goats digested sorghum straw better than sheep (Alhassan et al., 1986). In the production of sweet sorghum syrup, the leaves, and not the stems, are left on the field (Madibela et al., 2002).

Another way to improve the nutritive value of sorghum straw is to treat it. In India, urea, liquid ammonia and even animal urine were found to improve the degradability of straw, because these treatments increase the nitrogen content of the feed and thus the efficiency of the microbial population in the rumen (Dhuria et al., 2007). Treatment with NaOH was effective in increasing the in vitro DM digestibility (by 20 percentage points) of sorghum straw (Escobar et al., 1985). In Kenya, treatment with 5% NaOH of maize/sorghum straw reduced fibre by about 15%, increased in vitro DM digestibility by 8.5 percentage points and intake by about 60%. However, these enhancements failed to increase performance (average daily gain) in sheep and goats (Tessema et al., 1984). In India, fine grinding followed by treatment with lime (10 g Ca(OH)2/100 g DM) increased the in sacco DM degradability after 48 h of incubation from 54.1 to 89.2% (Gandi et al., 1997).

In dual purpose sorghum varieties, grain yield and forage quality are not inversely related, but stover yield is often insufficient. Genotypes promoting highly digestible OM intakes are only suitable for farmers with sufficient amounts of stover to allow the feeding of animals to appetite. When only restricted amounts of stover are available, it is more relevant to choose genotypes and feeding systems that promote high digestibility under restricted feed intake (Blümmel et al., 2003).

Rabbits 

Sorghum leaves and stalks

There are very few reports of feeding sorghum forage to rabbits. One study investigated the potential toxicity of first-cut sorghum leaves and stalks when distributed fresh as the sole feed for one month to six-month old rabbits, in comparison with fresh grass. Feeding sorghum stalks resulted in haematological abnormalities, which were probably due to the higher nitrate content: 1480 ppm in sorghum stalks vs. 850 ppm in sorghum leaves and 736 ppm in grass. An ancillary finding of this study was that rabbits more or less tolerated this imbalanced feeding system during the experimental period (Bhatti et al., 2011).

Sorghum stover

Non-mouldy sorghum stover can be used as a fibre source in complete feeds for rabbits. It was for example used at up to 20% of the control diet in a study of khat leaves (Catha edulis) utilisation by rabbits (Al-Habori et al., 2004).

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 90.0 2.1 86.7 94.9 11
Crude protein % DM 7.5 3.1 4.2 13.7 12
Crude fibre % DM 32.3 2.6 28.4 36.4 8
NDF % DM 68.7 6.2 58.7 73.3 6
ADF % DM 44.0 7.3 33.1 49.8 6
Lignin % DM 6.2 0.5 5.6 6.8 4
Ether extract % DM 1.4 0.3 0.8 1.7 10
Ash % DM 8.8 1.1 7.6 11.3 12
Gross energy MJ/kg DM 17.9 *
 
Minerals Unit Avg SD Min Max Nb
Calcium g/kg DM 1.8 0.6 1.0 2.8 7
Phosphorus g/kg DM 1.7 0.6 0.7 2.3 7
Potassium g/kg DM 15.6 7.0 7.0 25.5 7
Sodium g/kg DM 0.0 1
Magnesium g/kg DM 2.9 0.9 1.8 4.5 7
Manganese mg/kg DM 107 1
Zinc mg/kg DM 54 1
Copper mg/kg DM 7 1
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, Ruminant % 61.5 7.2 52.1 70.3 5 *
Energy digestibility, ruminants % 58.0 *
DE ruminants MJ/kg DM 10.4 *
ME ruminants MJ/kg DM 8.4 *
Nitrogen digestibility, ruminants % 50.9 15.4 37.6 70.6 5

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

References

Aguiar et al., 2006; Aguiar et al., 2006; Alibes et al., 1990; CIRAD, 1991; Cleasby et al., 1958

Last updated on 24/10/2012 00:45:05

Main analysis Unit Avg SD Min Max Nb
Dry matter % as fed 93.0 1.0 90.8 94.7 35
Crude protein % DM 3.7 1.2 1.8 7.7 40
Crude fibre % DM 39.5 3.7 31.6 46.8 36
NDF % DM 76.6 3.3 69.7 81.9 22
ADF % DM 48.2 4.0 39.1 55.6 23
Lignin % DM 7.3 1.5 4.4 9.3 23
Ether extract % DM 1.2 0.3 0.6 1.7 26
Ash % DM 7.5 2.0 3.9 12.0 41
Gross energy MJ/kg DM 18.1 0.3 18.1 20.1 6 *
 
Minerals Unit Avg SD Min Max Nb
Calcium g/kg DM 3.1 1.1 1.8 5.7 25
Phosphorus g/kg DM 0.7 0.4 0.3 1.7 27
Potassium g/kg DM 12.9 5.6 4.4 25.2 22
Sodium g/kg DM 0.2 0.1 0.0 0.3 12
Magnesium g/kg DM 2.5 0.6 1.5 3.8 23
Manganese mg/kg DM 124 73 22 227 12
Zinc mg/kg DM 24 24 7 97 12
Copper mg/kg DM 5 4 2 16 12
Iron mg/kg DM 1088 1
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, Ruminant % 53.0 9.1 40.6 69.8 8 *
Energy digestibility, ruminants % 49.3 *
DE ruminants MJ/kg DM 8.9 *
ME ruminants MJ/kg DM 7.3 *
Nitrogen digestibility, ruminants % 30.0 23.6 0.0 57.7 4

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

References

Alibes et al., 1990; CGIAR, 2009; Chandra et al., 1971; CIRAD, 1991; French, 1943; Gowda et al., 2004; Ncube et al., 1992; Nsahlai et al., 1996; Ohlde et al., 1982; Parigi-Bini et al., 1991; Patel, 1966; Richard et al., 1989; Savadogo et al., 2000

Last updated on 24/10/2012 00:45:05

Main analysis Unit Avg SD Min Max Nb
Dry matter % as fed 28.1 6.4 15.9 41.3 72
Crude protein % DM 8.2 3.2 2.5 16.3 203
Crude fibre % DM 33.6 5.2 22.6 43.2 133
NDF % DM 57.9 4.9 46.2 67.0 112
ADF % DM 35.0 4.3 27.9 45.0 54
Lignin % DM 3.3 1.2 1.4 6.7 52
Ether extract % DM 1.9 0.5 1.1 3.1 88
Ash % DM 9.1 2.2 5.4 13.7 197
Gross energy MJ/kg DM 18.1 *
 
Minerals Unit Avg SD Min Max Nb
Calcium g/kg DM 4.1 1.6 1.9 7.4 128
Phosphorus g/kg DM 2.0 0.8 0.8 3.8 125
Potassium g/kg DM 19.3 6.1 9.6 31.7 79
Sodium g/kg DM 2.5 4.6 0.1 9.4 4
Magnesium g/kg DM 2.2 0.4 1.6 3.6 79
Manganese mg/kg DM 82 68 37 160 3
Zinc mg/kg DM 45 18 26 69 4
Copper mg/kg DM 13 6 5 21 4
Iron mg/kg DM 919 1
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, Ruminant % 63.1 7.4 56.4 82.0 52 *
Energy digestibility, ruminants % 60.3 *
DE ruminants MJ/kg DM 10.9 *
ME ruminants MJ/kg DM 8.8 *
ME ruminants (gas production) MJ/kg DM 9.9 1
Nitrogen digestibility, ruminants % 60.5 5.8 50.6 67.0 8
a (N) % 22.0 1
b (N) % 66.0 1
c (N) h-1 0.050 1
Nitrogen degradability (effective, k=4%) % 59 *
Nitrogen degradability (effective, k=6%) % 52 *

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

References

Aguiar et al., 2006; Ahmed et al., 1983; CGIAR, 2009; Chafai, 1984; CIRAD, 1991; French, 1943; Fulkerson et al., 2008; FUSAGx/CRAW, 2009; Gowda et al., 2004; Holm, 1971; Kawas et al., 1995; Khanum et al., 2007; Olcese et al., 1951; Xandé et al., 1989

Last updated on 24/10/2012 00:45:06

Main analysis Unit Avg SD Min Max Nb
Dry matter % as fed 28.4 4.4 21.8 35.6 18
Crude protein % DM 6.7 1.3 4.2 8.4 25
Crude fibre % DM 32.8 5.9 20.7 41.6 20
NDF % DM 66.0 4.6 59.2 73.0 17
ADF % DM 41.8 5.3 30.4 50.3 21
Lignin % DM 7.4 1.7 4.1 10.4 17
Ether extract % DM 2.6 1.1 0.7 4.8 17
Ash % DM 8.8 2.3 5.0 14.1 30
Gross energy MJ/kg DM 18.1 18.1 18.8 2 *
 
Minerals Unit Avg SD Min Max Nb
Calcium g/kg DM 4.1 1.2 2.6 7.2 18
Phosphorus g/kg DM 3.0 1.0 1.5 4.8 18
Potassium g/kg DM 20.4 5.5 14.6 30.9 10
Sodium g/kg DM 6.3 6.8 0.4 15.6 4
Magnesium g/kg DM 2.2 0.7 1.4 3.5 10
Manganese mg/kg DM 24 7 17 32 3
Zinc mg/kg DM 37 30 45 2
Copper mg/kg DM 7 7 7 2
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, Ruminant % 64.3 3.4 63.3 70.1 3 *
Energy digestibility, ruminants % 60.3 *
DE ruminants MJ/kg DM 10.9 *
ME ruminants MJ/kg DM 8.9 *
Nitrogen digestibility, ruminants % 58.9 9.1 47.4 69.0 5

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

References

Adewakun et al., 1989; AFZ, 2011; Alibes et al., 1990; CGIAR, 2009; CIRAD, 1991; Hart, 1990; Henderson et al., 1984; Holm, 1971; IAV, 2009; Maben et al., 1971; Meschy, 2010; Parigi-Bini et al., 1991; Rahman et al., 1968

Last updated on 24/10/2012 00:45:06

Main analysis Unit Avg SD Min Max Nb
Dry matter % as fed 26.8 26.6 27.0 2
Crude protein % DM 8.1 1.8 5.9 11.5 7
Crude fibre % DM 35.9 5.6 26.4 42.4 7
NDF % DM 65.4 4.6 60.5 71.7 4
ADF % DM 41.8 3.9 37.9 47.0 4
Lignin % DM 3.4 1.1 2.2 4.8 4
Ether extract % DM 2.6 1.0 1.5 4.2 6
Ash % DM 16.8 5.3 6.1 21.6 7
Gross energy MJ/kg DM 16.8 *
 
Minerals Unit Avg SD Min Max Nb
Calcium g/kg DM 5.7 1.2 4.2 7.1 5
Phosphorus g/kg DM 3.5 2.0 1.3 6.1 5
Potassium g/kg DM 33.1 10.4 23.9 43.5 4
Sodium g/kg DM 15.2 1
Magnesium g/kg DM 3.2 0.5 2.6 3.8 4
Manganese mg/kg DM 48 45 52 2
Zinc mg/kg DM 43 37 49 2
Copper mg/kg DM 9 7 11 2
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, Ruminant % 59.5 *
Energy digestibility, ruminants % 55.4 *
DE ruminants MJ/kg DM 9.3 *
ME ruminants MJ/kg DM 7.5 *
Nitrogen digestibility, ruminants % 54.6 1

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

References

CIRAD, 1991; Maben et al., 1971

Last updated on 24/10/2012 00:45:13

References
References 
Datasheet citation 

Heuzé V., Tran G., Lebas F., Giger-Reverdin S., 2015. Sorghum forage. Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. http://www.feedipedia.org/node/379 Last updated on July 7, 2015, 11:53

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