Feedipedia
Animal feed resources information system
Feedipedia
Feedipedia

Maize stover

Datasheet

Description
Click on the "Nutritional aspects" tab for recommendations for ruminants, pigs, poultry, rabbits, horses, fish and crustaceans
Common names 

Maize stover, corn stover, maize straw, corn straw [English]; cannes de maïs, paille de maïs, tiges de maïs [French]; rastrojo de maíz, cañote de maíz; caña de maíz [Spanish]; Maisstroh [German];حطب الذرة [Arabic]; 玉米秸稈 [Chinese]; thân rơm ngô [Vietnamese]

Species 
Description 

Maize stover consists of the residues of maize (Zea mays L.) plants grown for grain and left in the field following the harvest. It includes stalks, leaves, husks, and cobs. Because the amount of maize dry matter left on the field is similar to the amount of dry grain produced, considerable quantities of maize stover are available. Maize stover is often considered as the best of the cereal stovers for livestock due to its higher protein and energy content. However, it remains a highly fibrous feed of limited digestibility and palatability that may require treatments to enhance its nutritional value.

Composition

Maize stover contains different plant parts in variable proportions. Stalks are the main component (40-60%), followed by leaves (20-30%), cobs (15-20%) and husks (10-15%) (Lizotte et al., 2015).

Utilisation

Maize stover is commonly left on the field or buried to provide organic matter to the soil (Chenost et al., 1991) but is also used to feed livestock:

  • Grazing. This is often done when stover is abundant in relation to livestock
  • Cut-and-carry after drying. This is done by stacking or baling, in the field or at the farm
  • Silage: it has to be chopped, moistened, well compacted and sealed (Suttie, 2000).
  • Feeding green maize stover tops is also practiced (Bwire et al., 2002).

Maize stover is valuable for litter and fuel, and may then include the roots and the stem bases (Suttie, 2000). Since the 2000s, maize stover as been considered as a potential feedstock for the production of cellulosic ethanol (Shinners et al., 2009; Tyndall et al., 2011). This renewed intererest in maize stover into cellulosic biofuels production has resulted in innovation and improvements in harvesting and processing (Casperson et al., 2018).

Distribution 

Maize stover is available wherever maize is grown for grain. Assuming a ratio of 0.8 t of dry stover per t of dry grain (Lizotte et al., 2015) and a worldwide maize grain production of 1100 million t in 2017 (FAO, 2019), the world production of dry maize stover is about 900 million t.

Processes 

Because maize stover is a fibrous feed with a low digestibility, many processes have been developed and tested in order to improve its nutritional value. These processes include physical treatements (grinding, extrusion), chemical treatments (urea, NaOH, CaO, ammonia, sulfuric acid), and biological treatments with microorganisms (fungi, bacteria) or mushrooms such as Pleurotus ostreatus. Chemical treatments have been widely used and can efficiently increase lignin solubilization and hydrolysis of cellulosic fractions, but their adverse effects on the environment and operator health and high operational cost may make these methods unsafe and noneconomical (Katoch et al., 2017). The Ruminant section of this datasheet presents some results obtained using processed maize stover.

Forage management 

Yield

The amount of stover produced depends on weather, soils and management practices like fertilizer and pest control applications (Pennington, 2013). The stover yield expressed in DM is usually comparable to that of dry grain produced. In Québec (Canada), the stover/grain ration observed over several years for different cultivars varied between 0.7 to 1.1. Stover DM yield varied from 7.0 to 10.5 t/ha (Lizotte et al., 2015). In Michigan (USA), the ratio varied from 0.3 to 1.2, with yields ranging from 1.3 to 8.4 t/ha. A "harvest index" calculated as the ratio between the amount of stover and the sum of stover + grain has been proposed to estimate the amount of maize stover available (Wilhelm et al., 2004). This index is typically of 0.4-0.5, though values ranging from 0.35 to 0.8 have been observed (CNC, 2002; Pennington, 2013). Stover DM yield tends to decrease during the grain harvest period: in a trial in Tennessee, DM yield peaked at 16 t/ha when stover was harvested at the time of grain physiological maturity (118 days after planting, grain moisture of 31%) and it was down to 8.2 t/ha 200 days after planting (Pordesimo et al., 2004).

Harvest

In temperate countries, maize stover is most often harvested as a dry product and packaged in large round or large square bales, typically involving as many as seven steps after grain harvesting (Shinners et al., 2009). Maize stover harvesting is typically difficult as it is often carried out in unfavourable climatic conditions, with short harvesting windows and frequent weather delays (CNC, 2002; Shinners et al., 2009). The soil may be bare with a reduced bearing capacity, or damaged during grain harvesting. The plants are partly lying on the ground and are more or less contaminated by soil, making cutting and collecting difficult, as the presence of soil may cause premature wear of the cutting elements. In France, it is possible to harvest 30 to 80% of the DM remaining in the field (CNC, 2002). In the US, harvesting efficiency ranges between 37% and 50% (Shinners et al., 2009). A higher efficiency has been obtained by harvesting wet stover immediately after grain harvest by combining shredding and windrow formation in one machine and then chopping with a forage harvester (Shinners et al., 2009).

In tropical countries where maize is usually harvested during the dry season, it is recommended that the stover should be harvested and stored as soon as possible after the grain harvest. Leaves at the time of grain harvest tend to be dry and brittle, and are easily lost when the rains come, or deteroriated by microbial attack and decomposition. Wet stover needs to be sun-dried prior to storage to avoid post-harvesting spoilage. However, physical handling exercise necessary for sun-drying may results in further loss of leaves and husks (Methu et al., 2001).

Storage

A trial in Michigan concluded that storing bales under cover (roof or plastic) provides opportunity for long-term storage (more than 120 days). Storing uncovered bales outside works though winter, but DM losses increase significantly when the weather warms up, particularly with high moisture bales. Higher moisture bales should be stored outside, away from buildings to avoid a fire hazard. It is feasible to keep them outside for a limited amount of time and still maintain nutrient quality, but they tend ot lose structural integrity after 120 days. Low moisture bales have better preservation in storage and keep their nutritive value over time, indoors or outdoors, though they have less nutrient content compared to higher moisture bales (Jean et al., 2017b).

Silage

Maize stover is difficult to pack. Silage must be harvested quickly after harvesting the grain (1 to 2 days) to avoid an excessive DM content. Fine chopping facilitates stackin and ensures good preservation. Loading in regular and thin layers (10 to 20 cm maximum) is imperative. If the stems are too dry, it is possible to add moist products such as forage rape. The silo must also be covered with soil or sandbags that will prevent air from circulating between the plastic sheeting and silage during silo operation. When harvested without soil at less than 30% DM, maize stover silage can be well compacted and preserved as well as whole plant silage; above this rate, losses can be significant (CNC, 2002).

Environmental impact 

Maize stover is often left on the field or buried. This practice is considered favourable to soil health, as it protects land against erosion and returns organic matter back to the soil (Wilhelm et al., 2004). In the USA, it has been estimated that about 25% of maize stover could be harvested sustainably under current crop rotation and soil tillage practices. Using no-till practices, the proportion could be increased to 50% because of better protection against erosion and enhanced long-term soil quality (Lizotte et al., 2015).

Nutritional aspects
Nutritional attributes 

Maize stover is a fibrous feed, usually of better nutritional quality than other cereral straws. Its protein content is often higher than 4% and can be as high as 9%. However, maize stover of very poor nutritional value, with protein < 4% is also reported. The crude fibre content is about 30%, lower than that of wheat straw (40%). Maize stover contains less lignified material, making it more digestible to livestock than straw. However, large differences in harvesting conditions (stage of maturity) and variations in the proportions of stalks, ears and leaves make it a highly variable product. 

Because the feed value of the stalks drops from harvest date, due to the weathering of the leaves and stalks, maize stover is better consumed the earliest after the grain harvest. This is particularly true when stover is grazed, as livestock eat the grain and leaves early in the grazing, leaving the lower-value stalks for later (Kyle, 2015).

Potential constraints 

Maize stover is frequently contaminated by fungi, as a consequence of wet conditions at harvest and during storage, resulting in the presence of mycotoxins (Skrinjar et al., 2011; Lanyasunya et al., 2005; Bottalico et al., 1989; Visconti et al., 1989). Lethal cases of equine leukoencephalomalacia (ELEM) caused by Fusarium contamination in maize stover have been reported in horses in Mexico (Reyes-Velázquez et al., 2018). Grazing maize stover after harvest is not considered to be a risk in cattle, they are not very sensitive to fumonisins (Damicone, 2017).

Ruminants 

In temperate countries, maize stover is generally considered as an adequate energy source for beef cattle, including heifers, steers, and cows, as well as maintenance and gestating ewes (Jordan, 1990; Russell, 1986 ; Jean et al., 2017a ; Kyle, 2011 ; Kyle, 2015). However, due to the relative low value of this forage and to its variability over time, ration balancing is critical when factoring stover into cattle diets, and a proper supply of energy, protein and minerals must be provided to meet nutrient requirements and performance goals (Jean et al., 2017b). In tropical and dry climate countries, maize stover is widely used for all types of livestock. In the central Kenya highlands, for instance, maize stover is the most abundant crop residue and it is often the sole forage offered to dairy cattle during the dry seasons (Methu et al., 2001).

Palatability

Maize stover has a large particle size, and livestock tend to sort through it to eat the smaller parts first - grain, cobs and leaves - and leave the stalks. In sheep, refusal up to 25-30% have been observed (Jordan, 1990). When maize stover is added to a total mixed ration, because cows can readily sort through the TMR, leaving the corn stalks in the bunk and having lower fiber intake than anticipated. Therefore, reducing the particle size before or during mixing will be important in reducing the risks for sorting (Eastridge, 2007).

Digestibility

The digestibility of maize stover is the highest at grain harvest and declines over time. A trial in Canada found that the in vitro DM digestibility started at 52% and then declined by 1.5 percentage point per week (Leask et al., 1973). Another trial in the USA also found that a reduction in in vitro DM digestibility for the fibrous parts of maize stover, with losses of 15-20 percentage points over three months, though the total yield of digestible DM decreased only slightly (Weaver et al., 1978). This reduction in digestibility does not seem to result primarily from increased lignification of the cell walls, but from an increase in the concentration of NDF because of the loss of cell solubles (Russell, 1986).

Grazing

Grazing maize stover can provide a low cost feed source for mid-gestation beef cows and maintenance and mid-gestation ewes, who can also glean the grains and cobs left on the field. About 50 cows can graze on 20 ha, or 20-25 ewes per ha, for one to two months. Because the animals tend to eat the kernels and cobs first, it may be necessary to restrict the grazing time or size so that the cows do not overload on grain, and to keep the energy intake more uniform. As the nutritive value of the stover decreases over time, so supplementation with hay will be required to meet protein and energy requirements, notably when the cows have eaten all the leftover grain. In automn and winter, it is important to pay attention to soil condition by having the animals graze only dried or frozen fields, and preventing them from grazing wet (thawed) ones (Kyle, 2015).

Cut and carry

Beef cattle

The utilisation of maize stover for beed cattle has been extensively studied in the United States. In Michigan, finishing steers in a feedlot operation could be fed a ration with up to 20% maize stover (DM basis) without significantly effecting performance. Cattle compensated for a lower energy diet containing less maize grain by increased intake when fed a 20% stover diet. Feeding stover had a significant effect on DM intake, but the carcass characteristics and weight gain remained similar among treatments (Jean et al., 2017a). In a trial in Nebraska, steers fed early harvested maize stover gained 180 g/d more and were 19% more efficient than those fed the late harvested stover (Berger et al., 1979).

Several studies have investigated the use of alkali treatment for improving the nutritive value of maize stover. In Indiana, several trials studied the value of ammoniated maize stover with positive conclusions. In 240 kg steers fed 900 g/d of grain, stover treated with ammonia at 2 or 3% DM increased DM intake, DM digestibility, and N retention compared to unammoniated stover fed with the same amount of supplement. Mature pregnant beef cows fed a similar diet with stover treated at 3.2% DM had higher weight gains and their condition score did not decrease unlike that of cows fed untreated stover or other diets, (Saenger et al., 1982). Treatment with NaOH of late harvested stover improved steer performance, increasing gain by 220 g/d and feed efficiency by 26%. The effect of NaOH treatment was less conclusive for early harvested stover, as it had no effect in one trial and was satisfying in another, where it increased gains by 210 g/d and feed efficiency by 20% (Berger et al., 1979).

However, NaOH is expensive, corrosive, poses human health risks, and the treated feeds may provide excess dietary sodium, so alternative methods, and particularly treatments with calcium oxide (CaO, quicklime) are now preferred. It has been shown that treatment of stover with 7% CaO and addition of water to 50% DM resulted in nine times greater release of glucose and xylose after incubation with cellulase (Donkin et al., 2013). Similar feedlot performance was achieved when high moisture and dry rolled maize grain was replaced by CaO-treated maize stover to a level of 20% of the ration (Shreck et al., 2012). When steer calves were fed CaO treated (5% of DM) or untreated maize stover with wet distillers grains plus solubles, treatment with CaO failed to improve performance and it was concluded that not treating maize stover was more economical (Shreck et al., 2014).

Dairy cows

In temperate countries, maize stover has limited use as a feed resource for lactating dairy cows given its low nutritional value but studies carried out since the 2010s have shown the potential of using CaO-treated maize stover in dairy diets (Casperson et al., 2018). The combination of CaO-treated maize stover and dried distillers grains could replace wild rye, maize silage, or maize grain to a level of 15% of diet DM without affecting DMI, milk production, or 4% FCM yield (Shi et al., 2015). However, replacing grain in the diet with alkali-treated maize stover at 13% of the diet DM reduced DMI and milk production (Cook et al., 2016). Short term studies indicate that maize stover treated with 5% CaO and added water to 50% dry matter can replace maize silage in diets for lactating dairy cows to at least 25% of the total ration (Donkin et al., 2013).

In tropical and dry climate countries, maize stover is sometimes the main forage fed to dairy cattle during the dry season. In central Kenya, the stover is usually chopped and offered as the sole forage, but depending on availability, the stover may be mixed with weeds or any available green materials. Stover is sometimes alternated with elephant grass to ensure that the latter is available for as long as possible. Offering maize stover in excess to dairy cattle was found to be an effective strategy to improve the intake of maize stover supplemented with cottonseed cake and increase milk production. (Methu et al., 2001).

Sheep

Feeding maize stover has been described as an opportunity to reduce the cost of feeding ewes during early gestation. However, it was found to be poorly palatable, with a 25-35%. Ewes weighing 80-90 kg consumed only 900 g/day of stover. Grinding the stalks increased intake by 10-15%, but the grinding costs ($10-15/t ) made maize stover less economically appealing. To utilize maize stover, it is recommended to supplement with either a protein and mineral supplement, or about half of the DM must be provided as alfalfa hay (Jordan, 1990).

Early studies indicated that pretreatment of corn stover with a combination of 2% NaOH and 2% CaO resulted in a 53% increase in feed intake in growing lambs and a 12% increase in DM digestibility (Oji et al., 1977). More studies indicate a 6 to 9% increase in total tract DM digestibility in lambs fed maize fibre pretreated with a combination of alkali and heat (Donkin et al., 2013).

Silage

Ensiled maize stover, when stabilized after 1 or 2 months, are comparable to a regular hay. Supplementation with protein-rich feed is necessary to fulfill animal requirements. Adding 10 g or urea per kg DM may allow a better nitrogen balance. When the DM content is lower than 30%, ammonia treatment is possible using the same process as the one used for whole-plant maize silage (CNC, 2002). Ensiled maize stover is mainly valuable for beef cattle and sheep, and of little value of dairy cows.

Beef cattle

It may form the basis of the diet of suckler cows at the end of gestation and at the beginning of lactation, and of beef heifers during winter. Suckler cows and beef heifers can eat 1.4-1.7 kg DM per 100 kg of liveweight of ensiled maize stover. For instance, a diet for beef cows may include up to 35-40 kg/day of ensiled stover. Young steers (> 240 kg) can consume up to 15-20 kg/day of that forage. In all cases, supplementation with protein sources, minerals and vitamins is necessary (CNC, 2002).

In Nigeria, ensiled maize stover treated with 4% urea fed to native Zebu cattle was found to be have a higher OM digestibility than the untreated silage (65% vs 51%) and to increase intake, but it did not prevent cattle weight loss (Alhassan et al., 1991).

Sheep

A comparison of various treatments of maize stover silage fed to sheep concluded that ammonia treatment (3%) was more effective in enhancing the DM intake by sheep than treatement with urea or poultry litter. However, treated or untreated maize stover always resulted in a lower DM intake than that obtained with the basal diet (Ali et al., 2009).

Green stover tops

Recent advances in feeding strategies include the use of green maize stover tops as fodder, sometimes supplemented with grain legume crops (Bwire et al., 2002). In Tanzania, green maize stover tops (including leaves and tassels) can be offered as feed to dairy cattle in semiarid regions during the dry season. Time of harvesting affected nutritive value, due to the rapidly declining quality when plant matter remains on the field (Shirima et al., 1994 cited in Bwire et al., 2002). Harvesting maize stover tops when still green led to higher OM digestibility (62-65%), crude protein level (5.2-5.9% DM) and metabolizable energy (8.6-9.0 MJ/kg DM) compared to later stages. Storing maize stover tops in a shed preserved nutritive value much better than laying and stacking them in the field. Green maize stover tops supplemented with lablab forage led to performance similar to that obtained with a grass hay mixture, and to higher milk production (5 kg/d) and voluntary dry matter intake (8 kg DM/d including 5 kg of green maize stover tops) (Bwire et al., 2002).

Rabbits 

Maize stover in considered as a traditional source of fibre in rabbit feeding (Rivera et al., 2004; Zanaty et al., 2000; Fernandez-Carmona et al., 1996; Jeroch et al., 1990; Fekete et al., 1986). It was for example introduced at 3 to 8% as a fibre source in experimental diets formulated to study other feeds (Safwat et al., 2015). In studies conducted in Egypt and Hungary, maize stover was introduced successfully at up to 15-20% of the diets, though feed intake and growth performance were impaired where a higher inclusion rate (30%) was used (Tag-El-Din et al., 1999; Gippert et al., 1988). A more recent study in Nigeria could introduce local maize stover in the diet of growing rabbits at 60% without impairment of growth or slaughter performances, but final results were altered with the diet containing 70% of maize stover (Jokthan et al., 2010). The apparent discrepancy between these results (maximum level of 15-20% or 60%) may probably be explained by differences in contamination by mycotoxins of the maize stover samples in these studies. Rabbits are sensitive to very small quantities of mycotoxins, 10 to 100 times lower than those able to disturb ruminants, and the the first effect of mycotoxins is a reduction of feed intake (Mézes et al., 2009; Lebas et al., 1998). If free of mycotoxins, maize stover may be considered as a suitable source of fibre for rabbits with a low content of protein. Digestibility of energy and crude proteins according to different sources are presented in the table below.

Source Energy digestibility (%) Digestible energy (MJ/kg DM) Crude protein digestibility (%)
Fekete et al., 1986 54 9.35 56.0
Jeroch et al., 1990 69 12.97 -
Fernandez-Carmona et al., 1996 27.8 § 5.0 73.8
Kong et al., 1997 59.6 10.8 40.6
Su et al., 2012 43.3 6.84 § 54.8

§ Value calculated according to authors results and average data

Results are relatively variable between studies, most probably due to the type of maize used and the harvest conditions. On average values of 9.0 MJ /kg DM for the DE content and 56.3% for proteins digestibility may be considered as suitable for the introduction of maize stover in rabbit feeding.

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 29.6 6 17.4 54.2 227  
Crude protein % DM 6.8 1.5 2.5 11.1 247  
Crude fibre % DM 30 3.1 21 37.4 222  
Neutral detergent fibre % DM 69.9 9.1 53.9 91.3 40  
Acid detergent fibre % DM 39.6 7.6 28.8 58.6 35  
Lignin % DM 5.6 1.8 3.7 12.1 31  
Ether extract % DM 1.8   1.2 2.2 4  
Ash % DM 6.8 1.3 4 14.5 236  
Insoluble ash % DM 2.2   0.7 3.3 3  
Gross energy MJ/kg DM 18.2         *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 3.3 0.8 2.4 4.3 6  
Phosphorus g/kg DM 1.6 0.7 0.9 2.5 6  
Potassium g/kg DM 16.8 4.5 11.9 24 5  
Sodium g/kg DM 0.06       1  
Magnesium g/kg DM 2.1   1.6 2.6 3  
Zinc mg/kg DM 44       1  
Copper mg/kg DM 18       1  
Iron mg/kg DM 975       1  
               
Ruminants nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 59.3   51.1 61.5 3 *
Energy digestibility, ruminants % 56.7         *
DE ruminants MJ/kg DM 10.3         *
ME ruminants MJ/kg DM 8.4         *
Nitrogen digestibility, ruminants % -37       1  
Nitrogen degradability (effective, k=6%) % 42       1  
Nitrogen degradability (effective, k=4%) % 47         *
a (N) % 30       1  
b (N) % 55       1  
c (N) h-1 0.017       1  
Dry matter degradability (effective, k=6%) % 30 13 14 45 8  
Dry matter degradability (effective, k=4%) % 32   17 47 3 *
a (DM) % 13 11 0.9 31 8  
b (DM) % 50 11 34 69 8  
c (DM) h-1 0.025 0.009 0.01 0.037 8  
               
Rabbit nutritive values Unit Avg SD Min Max Nb  
Energy digestibility, rabbit % 49.7         *
DE rabbit MJ/kg DM 9.1          
MEn rabbit MJ/kg DM 8.9         *
Nitrogen digestibility, rabbit % 45.3         *

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

Last updated on 06/11/2019 16:30:50

Main analysis Unit Avg SD Min Max Nb  
Dry matter % as fed 92.8 2.8 84.1 98 76  
Crude protein % DM 3.9 1.5 1.8 11.5 80  
Crude fibre % DM 40.7 4.1 29 48.2 62  
Neutral detergent fibre % DM 75 13.6 39.5 87.8 60  
Acid detergent fibre % DM 49.6 6.2 37 59.4 57  
Lignin % DM 7.4 2.4 3 13.5 53  
Ether extract % DM 0.9 0.5 0.2 2.2 42  
Ash % DM 7.1 2 3.9 12.9 73  
Insoluble ash % DM 2.1 1.5 0.5 8.5 32  
Starch (polarimetry) % DM 11.4   10.9 11.9 2  
Gross energy MJ/kg DM 18.2         *
               
Minerals Unit Avg SD Min Max Nb  
Calcium g/kg DM 3.2 1.8 1.6 11.7 38  
Phosphorus g/kg DM 0.8 0.6 0.2 2.6 37  
Potassium g/kg DM 14 6.3 5.4 28 30  
Sodium g/kg DM 0.24 0.26 0.04 0.75 13  
Magnesium g/kg DM 2.3 0.3 1.7 3 29  
Sulfur g/kg DM 0.9   0.9 0.9 3  
Manganese mg/kg DM 107 78 16 242 16  
Zinc mg/kg DM 17 8 9 32 16  
Copper mg/kg DM 4 1 2 6 16  
Iron mg/kg DM 975          
               
Secondary metabolites Unit Avg SD Min Max Nb  
Tannins (eq. tannic acid) g/kg DM 2   2 2 3  
               
Ruminants nutritive values Unit Avg SD Min Max Nb  
OM digestibility, ruminants % 49 6.1 46 61.4 6 *
Energy digestibility, ruminants % 46.8         *
DE ruminants MJ/kg DM 8.5         *
ME ruminants MJ/kg DM 6.9         *
Nitrogen digestibility, ruminants % 15.5 23.4 -25.2 39.7 6  
Nitrogen degradability (effective, k=6%) % 45       1  
Nitrogen degradability (effective, k=4%) % 48       1 *
a (N) % 38       1  
b (N) % 31       1  
c (N) h-1 0.02       1  
               
Rabbit nutritive values Unit Avg SD Min Max Nb  
Energy digestibility, rabbit % 49.8         *
DE rabbit MJ/kg DM 9.1       1  
MEn rabbit MJ/kg DM 8.9         *
Nitrogen digestibility, rabbit % 62.3   56 68.5 2  

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

Last updated on 06/11/2019 16:27:09

References
References 
Datasheet citation 

Heuzé V., Tran G., Lebas F., 2019. Maize stover. Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. https://www.feedipedia.org/node/16072 Last updated on November 6, 2019, 16:17

Image credits