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Maize cobs

Datasheet

Description
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Common names 

Maize cobs, corn cobs, corncobs [English]; rafles de maïs [French]; corontas de maíz [Spanish]

Species 
Related feed(s) 
Description 

Maize cobs are a by-product of the maize crop, consisting of the central fibrous rachis of the female inflorescence (the maize "ear"). While the whole maize ear (with the grains, with or without the husks) is also sometimes called a maize cob, this datasheet concerns only the maize cob without the grains. The development of maize processing in the 20th century resulted in an increase in the volumes of this by-product (Lenz, 1948). About 180 kg of cobs are obtained from each ton of maize shelled (Evers et al., 1994). In the USA, it was estimated that about 50 million t of cobs were produced annually in the 2000s, most of them being left on the field (Jansen, 2012), and maize cobs are a major by-product in many maize producing countries.

Maize cobs are a highly fibrous product with many agricultural and industrial applications. In agriculture, they are used for fuel, litter for poultry and other animals, mulch and soil conditioner, and as fodder for ruminants despite their low nutritive value (Evers et al., 1994; Jansen, 2012). Their absorbency and abrasiveness makes them useful for several industrial applications. They can absorb finishing fluids, oil and water in industrial applications, and also help to clean up industrial or environmental spills. They are excellent carriers for vitamins and antibiotics in animal feed, and for herbicides and pesticides in lawn care products. They are used for the production of chemicals such as furfural or the sugar replacement xylitol. Maize cobs are used to blast and polish many materials, from jewellery, nuts and bolts, to golf club heads. More recently, maize cobs were reported to be a potential cheap and promising source for sustainable energy production (Evers et al., 1994; Jansen, 2012; Göhl, 1982).

Distribution 

Maize cobs are available in the vicinity of maize processing facilities and all households where maize is the staple.

Nutritional aspects
Nutritional attributes 

Maize cobs are a feed ingredient of low nutritive value, roughly similar to straw or a poor hay. Maize cobs contain little protein (about 5% DM) and are mostly composed of fibre (NDF more than 80% DM). However, the lignin content is relatively low for such a fibrous product (about 6% DM).

Ruminants 

Maize cobs are rich in fibre and poor in protein, and are thus a low-quality roughage. Despite this low value, their wide availability, large quantities, easy and cheap procurement, and also their large cellulose and hemicellulose reserves enhance their utilization as energy sources in ruminant feed, particularly in areas or during times where better ingredients are not available (Adebowale, 1992). In Nigeria, for instance, maize cobs are an important crop residue used by livestock farmers during the dry season, at a period when they are relatively available and abundant (Ogunleke et al., 2014). In Thailand, maize cobs have been described as the most prominent crop by-product (Wachirapakorn et al., 2014). However, the high lignocellulosic content of the residues requires supplementation, processing, or both. For efficient utilization, supplementation with green forage or browse plants, or readily available source of carbohydrates and nitrogen such as cassava tops or peels, is essential for satisfactory production. Numerous experiments have also demonstrated the benefits of treating maize cobs with alkali (especially NaOH and urea), but such chemicals may be too expensive to buy in developing countries and/or too dangerous to handle in smallholder farming situations (Adebowale, 1992).

Palatability

Maize cobs are not very palatable to ruminants (Göhl, 1982). Adding 1% molasses may help to improve intake (Ndlovu et al., 1985).

Digestibility and degradability

Reported OM digestibility values vary greatly, from 15-29% to more than 50% (Kategile et al., 1979; INRA, 2007). In vitro DM digestibility at maturity was reported to be in the 50-56% range (Masoero et al., 2006). Like other fibrous materials, treating maize cobs with alkali improves their nutritional value. The in vivo DM digestibility of maize cobs increased from 54 to 62% when they were treated with 4% NaOH, and to 66% when they were treated with Na2O2 (Klopfenstein et al., 1972). In Tanzania, a series of experiments with lambs confirmed that NaOH treatment improved DM and OM digestibility by 5-10 percentage points, though lower OM digestibility values were reported (15-29% for untreated cobs and 30-47% for treated cobs) (Kategile et al., 1979). Urea treatment (6.5%) increased the effective degradability of the DM and NDF of maize cobs from 23 to 32% and from 25 to 31%, respectively (Ramirez et al., 2007). Supplementation with alfalfa hay (30% of the total feed) of a maize cobs-based diet fed to mature sheep increased the rates of evacuation of indigestible material from the rumen (Ndlovu et al., 1985). Grinding may improve the digestion rate of maize cobs and feed efficiency (Ndlovu et al., 1985; Murali et al., 1989), and many experiments are based on ground maize cobs.

Maize cobs in supplemented diets

Supplementation of maize cobs with sources of energy and nitrogen, involving methods that are realistic of small farm situations, is often a cheaper and simpler way of feeding them than chemical treatment (Adebowale, 1992). Grinding and/or pelleting are recommended.

Dairy cows

Maize cobs have contributed to diets for dairy cows for many years in the USA. When fed with restricted grain rations, ground maize cobs have replaced up to 60% of the roughage (alfalfa hay or alfalfa-brome hay) without affecting milk production or composition, although feed intake was reduced when maize cobs were the only source of roughage (Lassiter et al., 1958). Ground maize cobs replacing 50% of alfalfa-grass hay resulted in a lower milk yield but in higher weight gain (Graf et al., 1953). Ground maize cobs included at 20% of the ration were a better roughage than ground alfalfa hay, and equal to chopped alfalfa hay, for maintaining feed intake and milk production, but neither cobs nor alfalfa hay maintained the pretrial milk fat concentrations (Emery et al., 1964). In Thailand, feeding a diet containing 14% protein with maize cobs as a roughage source (20% in the total mixed ration) was adequate for supporting crossbred Holstein Friesian lactating dairy cows producing 11-13 kg milk/d (Wachirapakorn et al., 2014).

Growing cattle

In the USA, ground maize cobs could be used successfully in place of either dehydrated alfalfa or soybean flakes, as the major roughage in balanced high-roughage pelleted diets for dairy calves (up to 57% cobs in some diets) (Hibbs et al., 1978). In India, maize cobs were incorporated at 50% of the diet as the sole source of roughage in complete feeds of crossbred bulls. There were no deleterious effects, and grinding the cobs through 8-mm sieve was considered optimum (Murali et al., 1989). In Nigeria, 20 White Fulani steers were fed ad libitum on treated and untreated maize cobs with fresh Siam weed (Chromolaena odorata) (2 kg/head/day). Live-weight gain improved from a loss of 0.32 kg/d, when animals were fed untreated maize cobs, to a gain of about 0.48 kg/d, when cobs were treated and supplemented with Siam weed. Animals on untreated maize cobs were taken off the experiment within 3 weeks because of weight loss (Adebowale, 1992).

Sheep

In Nigeria, maize cobs supplemented with forage legume improved sheep performance, the highest feed intakes, weight gains and digestibilities of DM, protein and fibre being observed with added Leucaena leucocephala and Gliricidia sepium forage (Fasae et al., 2014). In West African Dwarf sheep, a diet based on 75% maize cobs and 23% brewers grain resulted in lower growth and feed use efficiency than a diet containing 50% cowpea husks (Vigna unguiculata), 25% maize cobs and 23% brewers grain (Ososanya et al., 2013). In India, ground maize cobs (8-mm sieve) were fed ad libitum, either as a mash or pelleted, as the roughage for adult sheep (with 250 g/d of concentrate mixture) without any deleterious effect, but pelleting improved nutrient utilization (Reddy et al., 1991). In lambs, ground maize cobs completely replaced finger millet straw (Eleusine coracana) in diets made of 50:50 roughage:concentrate (Senani et al., 2013).

Goats

In Nigeria, inclusion of up to 30% maize cobs in the diets of West African Dwarf goats (supplemented with brewers grains, wheat offal and palm kernel cake) gave the best growth performance. There were no deleterious effects on the haematological and serum biochemical parameters and, therefore, they were considered safe to include in ruminant diets up to 30% (Ogunleke et al., 2014). In India, adult goats were maintained on a diet of 60% maize cobs and 40% commercial mixture (Rajmane et al., 2000). Ground maize cobs (8-mm sieve) were fed ad libitum, either in a mash or pelleted, as roughage for adult goats (with 250 g/d of concentrate mixture) without any deleterious effect, but pelleting improved nutrient utilization (Reddy et al., 1991).

Chemically treated maize cobs

Numerous trials conducted in the USA in the 1970s showed that ensiled maize cobs treated with NaOH, KCl or Ca(OH)2 (or combinations of these treatments) gave similar or even better performance in steers and lambs than maize silage, even when maize cobs were included at 70-80% of the diet, provided that the diet was adequately supplemented (see review by Demarquilly et al., 1976).

Dairy cattle

In crossbred dairy cows in Pakistan, ensiling maize cobs treated with 5% urea, with an additive of 6% maize dextrose, improved N retention and dairy performance compared to urea-treated cobs ensiled without dextrose (Khan et al., 2004).

Growing cattle

In the USA, steers fed 80% ensiled maize cobs treated with 3% KCl had a daily gain almost twice that of steers fed maize silage (0.73 vs. 0.30 kg/d) (Koers et al., 1970).

Swamp buffaloes

Ground maize cobs fed to swamp buffaloes with urea at 15 g/kg were efficiently utilised in the rumen, and thus provided good fermentation end-products and an improved rumen ecology (Wanapat et al., 2009).

Sheep

In the USA, lambs fed ensiled maize cobs treated with 4% NaOH had average daily gains similar to those obtained with maize silage (Koers et al., 1972). In rations for growing lambs, treating and ensiling ground maize cobs with 3% NaOH plus 1% Ca(OH)2 increased average daily gain, feed intake and feed efficiency over cobs treated with 4% NaOH (0.15 kg/d vs. 0.12 kg/d), possibly because of the lower concentration of Na (Rounds et al., 1976). In Egypt, feeding rams ad libitum with maize cobs treated with 1% urea (supplemented with 500 g/d of a commercial mixture) had beneficial effects on body weight, daily gain and reproductive performance (testosterone production, semen quality, ram fertility) (Megahed et al., 2006).

Pigs 

Maize cobs are rich in fibre and have a low protein content and are, therefore, not recommended for pigs, except for sows, where the use of bulky diets diluted with fibrous feedstuffs has beneficial effects on body condition and some traits of reproductive performance. In a trial in Canada, the growth of the litter was increased by approximately 20% during the second parity when a bulky diet based on wheat bran (43%) and maize cobs (53%) was fed during the first and second parities (Matte et al., 1994). In Zimbabwe, the inclusion of 10 to 30% maize cobs in the diets of indigenous Mukota pigs and exotic Large White pigs resulted in a decrease of performance (growth, intake and feed conversion ratio) in both breeds, but Mukota breeds were less affected (Ndindana et al., 2002).

Poultry 

Maize cobs are rich in fibre and have a low protein content and are, therefore, not generally recommended for poultry. However, bulky diets may be more appropriate in the tropics where feed requirements are low due to high ambient temperatures. In a trial in Nigeria, pullets fed a diet containing 10% maize cobs reached maturity earlier, but birds fed 20% maize cobs did not come into lay within the time frame of the experiment. Birds fed maize cobs at 15% of the diet had a nitrogen retention identical to the control (Longe et al., 1989). In Ghana, diets containing up to 7.5% ground maize cobs fed ad libitum to commercial broiler chickens did not alter growth performance, carcass yields, health and biochemical indices (Donkoh et al., 2003).

Rabbits 

Maize cobs are generally considered as a potential source of fibre in rabbit feeding (Onifade et al., 1999). They are actually used as either one or the main source of fibre in basal diets for various experiments. In the latter case the inclusion levels vary from 5-6% to 30-33% (Arruda et al., 2003; Muriu et al., 2002; Scapinello et al., 2000). For specific studies, such as digestibility studies, it was employed at up to 40% (Gippert et al., 1988a). Nevertheless, when increasing proportions of maize cobs are studied, best growth results, i.e. results non significantly different from the basal diet, are observed with an inclusion level that does not exceed 10-15% (Marai et al., 1979; Gippert et al., 1988bEleraky, 1996).

The digestible energy content of maize cobs is similar to that of wheat straw (Zanaty et al., 2000) or a little bit higher (Gippert et al., 1988a). In addition to the very low protein content, it must be pointed out that these proteins are deficient in lysine (as are those of maize grain) but also deficient in sulphur-containing amino acids.

Despite the fact that maize cobs could be considered as a valuable source of relatively digestible fibres (Gippert et al., 1988a; Zanaty et al., 2000), this by-product must be employed with caution because of the very high risk of contamination by mycotoxins. Maize by-products are frequently infested by toxin-producing moulds (Mézes et al., 2009), and mycotoxins are more concentrated in the maize cobs than in the grain of the same maize ears (Perkowski et al., 1991). The toxicity of these mycotoxins is well documented in the rabbit (Mézes et al., 2009). Very low levels (1.9 mg/kg of final diet) of fumonisin are tolerated by reproducing rabbits (Idahor et al., 2008), but a higher level of 12 mg/kg is toxic for rabbits. However, the same level of fumonisin is well tolerated by ruminants or poultry, for which the recommended maximum level is 5 to 10 times higher (Ewuola et al., 2008).

Using maize cobs as source of fibre in rabbit feeding is thus possible only if safer fibre sources are not available. In this case great attention must be paid to potential fungal contamination issues.

Nutritional tables
Tables of chemical composition and nutritional value 

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 91.5 1.9 87.2 95.3 123  
Crude protein % DM 4.4 1.6 1.9 8.8 90  
Crude fibre % DM 34.9 3.6 29.2 42.7 125  
NDF % DM 87.8 3.9 80.1 94.4 56 *
ADF % DM 46.3 3.8 39.8 54.6 59 *
Lignin % DM 6.3 1.3 4.3 9.1 34 *
Ether extract % DM 0.6 0.2 0.3 1.1 73  
Ash % DM 3.6 1.6 1.3 7.3 92  
Starch (polarimetry) % DM 10.7   10.2 11.1 2  
Gross energy MJ/kg DM 18.5 1.3 17.4 20.5 4 *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 1.4 0.9 0.1 3.5 59  
Phosphorus g/kg DM 0.7 0.3 0.2 1.2 59  
Potassium g/kg DM 4.8 1.2 3.1 7.3 17  
Sodium g/kg DM 0.1 0.1 0.0 0.2 4  
Magnesium g/kg DM 0.4 0.3 0.1 0.9 17  
Manganese mg/kg DM 26 18 11 50 4  
Zinc mg/kg DM 32 31 12 77 4  
Copper mg/kg DM 8 7 3 18 4  
Iron mg/kg DM 16       1  
               
Ruminant nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 49.2         *
Energy digestibility, ruminants % 45.5         *
DE ruminants MJ/kg DM 8.4         *
ME ruminants MJ/kg DM 6.9         *
               
Poultry nutritive values Unit Avg SD Min Max Nb  
AMEn poultry MJ/kg DM 3.2   3.1 3.3 2  
               
Rabbit nutritive values Unit Avg SD Min Max Nb  
Energy digestibility, rabbit % 34.5         *
DE rabbit MJ/kg DM 6.4   5.0 7.8 2  
MEn rabbit MJ/kg DM 6.2         *
Nitrogen digestibility, rabbit % 62.6   51.3 73.9 2  

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

References

AFZ, 2011; Alibes et al., 1990; Aufrère et al., 1988; Bhatti et al., 1995; Chandra et al., 1971; CIRAD, 1991; Cozzi et al., 1993; Embrapa, 1991; Enueme et al., 1987; Fernandez Carmona et al., 1996; Gippert et al., 1988; Longe et al., 1988; Onwuka et al., 1997; Peteva-Vantcheva et al., 1976; Rajmane et al., 2000; Sen, 1938; Trillaud-Geyl, 1992

Last updated on 21/02/2015 00:28:44

References
References 
Datasheet citation 

Heuzé V., Tran G., Lebas F., 2016. Maize cobs. Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. http://www.feedipedia.org/node/718 Last updated on August 3, 2016, 17:07

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