**2. Global cereal production and utilization**

## **2.1 Global cereal production**

Cereals in their broad category are historically the major type of crops produced and traded across the world for food, feed and industrial uses [8]. In 2019, a global total of 2 719 million tonnes of cereals were harvested on 6,006 million ha of land [15]. This represents 60% and 50% of global food production on all cropped land, respectively. Of all the cereals produced in 2019, Africa accounted for 46.9%, Asia 49.1%, Europe 3.7%, the Americas 0.3% and Oceania 0.1% [15]. For decades, global leaders in cereal production are the United States of America, China and India [2]. However, different individual cereals are produced in large quantities in different regions of the world with the distribution driven by the prevailing climatic conditions, soil types, and general preference by local consumers. For instance, sorghum is widely produced and consumed in Africa while rice is widely produced and consumed in Asia [16]. Cereals including wheat, maize, rice and sorghum (*see* **Figure 1**) have a global cropping area of almost 700 million ha and together, they supply approximately 50% of the world's caloric intake [17]. At the global scale, wheat is the most important food security crop with a production of 750 Mtonnes on about 220 Mha in 2017 [11], followed by maize, rice, barley and

*Building Stress Resilience of Cereals under Future Climatic Scenarios: 'The Case of Maize… DOI: http://dx.doi.org/10.5772/intechopen.96608*

**Figure 1.**

*Major cereals produced for food and feed on the global scale.*

sorghum [8]. These are the major cereals produced across the world for human consumption and industrial utilization [7].

Global production of cereals is projected to increase as new crop production technologies are discovered and old ones being improved. The increase is projected to be 13% between 2015 and 2027 [18]. This projected increase in global production is attributed to the expected increase in production area and yield per area [18]. In 2020, global cereal production was expected to reach a record high of 2 742 million tonnes, which is an increase of 1.3% from the production in 2019 [2]. Area under wheat and maize are projected to increase by 1.4% and 3.2% respectively while other coarse grain cereals such as sorghum and barley are expected to increase by 2.4% by 2027 [18]. Global yields for wheat, maize and rice are projected to increase by 9%, 10% and 12% respectively between 2015 and 2027 [18].

In Africa and Asia, sorghum is a primarily produced as a subsistence crop using open pollinated varieties with low or no inputs and thus the productivity is usually very low, averaging 1.2 t/ha [19]. Production of sorghum in these regions is declining due to lack of established markets, consumer preferences and social pressure [19]. However, this decline in production is expected to be offset by increased production in the developed world, where demand is projected to increase as modern high yielding sorghum hybrids are becoming popular.

#### **2.2 Global cereal utilization**

The main uses for cereals are as food for human consumption in assorted whole grain and processed products, as stockfeed for animals such as pigs, cattle and poultry, and as raw materials for industrial production of chemicals and other nonfood products. Given the importance of cereals as staple crops and the discrepancy between consumption and production in many countries, increase in cereal production can significantly reduce prevalence of undernourishment and hunger, thereby improving food and nutrition security on the global scale.

#### *2.2.1 Human food uses*

All major cereals are generally prospective sources of food for consumption by both humans and animals for energy and general nutrition [20, 21]. Cereals are nutritionally rich with very high starch content to meet human and animal energy needs [20], some harbor proteins, but in low quantities [22], but they are limited for most of the important micronutrients for a healthy being such as zinc, iron [23], and some vitamins [24], although nutritional levels vary between crop species and varieties. The most important cereals worldwide are rice, wheat, maize, barley, and sorghum [21]. Due to the ever increasing human population, demand for cereals is expected to increase [21, 25]. The increasing demand for food weighs mainly on cereals such wheat, rice and maize which are some of the most important global sources for energy and nutrition.

In terms of total global cereal consumption, wheat provides 41% of the calories and 50% of the proteins [26]. In developing countries, it provides about 18% of daily caloric needs as compared to 19% of globally and 21% in high income countries [26]. It is usually ground to different flour types according to the rate of extraction and the flour is used to produce a wide range of products such as different bread types, cakes, biscuits, breakfast cereals, noodles, pies, pastries, bran, and alcoholic beverages [12]. Traditionally, wheat was not a crop of economic importance in some regions such as sub-Saharan Africa (SSA) but, it is now gaining popularity, especially in the urban areas [11].

Sorghum is mostly important as a food crop in the tropics and subtropics, particularly in Africa and Asia, where it is grown as a yield bank although it is now losing its popularity to maize. Like wheat, sorghum is mainly consumed after processing into flour and is used for baking and brewing purposes [19]. The flour which comes in different colors due to different grain colors (i.e., red, yellow and white) is used in baking and cooking. Sorghum colored four is now being considered as an alternative to using artificial food coloring products in production of cakes (velvet cake) [27]. Sorghum leaf sheaths can be used to produce an orange/red food dye that comes from its high content of antioxidants [27]. Its nutritional value and preference over wheat is that it is gluten free and has high content of several antioxidants and micronutrients that offer health benefits to humans [19]. Although sorghum is gaining importance as a nutritionally-rich food crop, its consumption in the developing world is declining [19]. In order to offset this narrative, the benefits of growing and consuming sorghum need to be effectively communicated in the developing world [19].

Maize is one of the most important food crops worldwide [16]. It is of great importance as a food and nutrition crop in SSA where more than 300 million people depend on it as their staple [16, 28]. Of all the major cereals, maize is eaten is several dishes and preparations more than all of them. For instance, the physiologically immature maize cobs are roasted or boiled and consumed as a snack, dry maize grain can swell and burst when heated to produce popcorn (i.e., a popular snack food), dry milling of maize grain produces maize meal, corn flour, and corn oil [16, 28]. Maize flour is used to make porridges, soups, pastes and for baking [29]. Various alcoholic and non-alcoholic beverages are prepared from maize flour [16]. Maize also produces a syrup which is used as a sweetener in food production [16]. Global maize consumption is projected to increase by 16% by 2027 and the increase is expected to be highest in the developing countries [18].

Rice is the principle food crop for more than 50% of the world's population [30, 31]. Ninety percent of the global rice is consumed in Asia where nearly 2.4 billion depends on it as a staple [2]. It provides two thirds of all calories to Asians who eat rice-based diets [2]. On a global level, rice contributes about 19% and

*Building Stress Resilience of Cereals under Future Climatic Scenarios: 'The Case of Maize… DOI: http://dx.doi.org/10.5772/intechopen.96608*

13% of the calories and proteins, respectively [26]. Rice consumption is on the rise particularly among urban populations in traditionally non-rice eating regions such SSA and this is expected to accentuate the global rice demand [32]. The bulk of the rice produced worldwide is consumed in the form of rice kernels, rice noodles and other rice-based value-added products such as breakfast cereals, gluten-free rice pasta, rice flakes and crackers [32].

#### *2.2.2 Livestock feed uses*

Maize, wheat, rice, and sorghum are primarily grown for human consumption, but they are also extensively used directly as animal feed or as inputs in the production of livestock feed [33]. Approximately 30% of global cereal production goes toward production of livestock feeds and this uses about 40% of global arable land [33]. This has led to some global debates on the competition between livestock and humans for land and other resources required in the production of crops for animal feed [33, 34]. Due to their high starch content, animal feed formulation predominantly comprises cereal grains or their by-products as energy sources [34]. Traditionally, cereal grains and straw were used to feed animals directly, but, with the advent of modern stockfeed formulations these crops are being used as ingredients in the manufacture of commercial rations especially for beef and dairy cattle, pigs, and poultry [35]. Cereals are used for animal feed in different ways. Maize, wheat and sorghum grains can be directly fed to livestock such as poultry and cattle (beef and dairy) [36] or can be processed and used as ingredients in production of feed. The stover can be used as dry grazing material or harvested for feeding [36, 37], whole plants (maize and sorghum) can be harvested for silage and fed to animals after ensiling [36]. Demand for cereals for livestock feed production is expected to increase as demand for animal products is increasing in many parts of the world [33]. The projected increase in demand for animal products is driven by human population growth, rising incomes and urbanization [33] and dietary preference towards western diets.

Maize is the major cereal used as livestock feed directly or as an ingredient in livestock feed production for swine, poultry, and cattle [36]. In the U.S, approximately 42.9% of maize grain is fed to livestock and poultry while only 11.2% is used for human consumption [36]. In Pakistan and some Asian countries, maize is the second most important cereal in the production of livestock feed, where the cereal component of poultry feed is composed of 40% maize, 40% rice by-products, 18% wheat and 2% sorghum [35]. In Africa, maize grain is mainly used for human consumption, while animals particularly cattle, is fed on dry maize fodder in winter. In some East and Southern African countries such as Ethiopia and Tanzania, dual-purpose maize varieties with increased fodder quantity combined with high grain yield are preferred by some rural farmers [38].

Wheat is usually not used in commercial stockfeed formulations. Its use in poultry feed formulations in Pakistan does not exceed 15% due to its negative effect on egg laying [35]. The same goes to rice, in which milled rice is not directly incorporated into livestock and poultry rations, but its by-products such as rice bran, rice tips, rice polish are utilized for commercial poultry and livestock feeds [35]. Use of rice straw as a source of feed for ruminant animals is limited due to high polysaccharides, lignin and silica content which reduce degradability by ruminal microorganisms [37]. However, it is still used for animal feed in some southeast Asian countries such as Thailand and Indonesia where rice straw is abundant due to high rice production [37]. Sorghum grains are widely used in production of poultry feeds. After harvesting, sorghum stover is used as a dry fodder just like other cereals. Sorghum stover represents up to 50% of the total value of the crop and its value

and contribution to feed and food security increases in drought years [35]. Sorghum is an important crop that serves multiple purposes as human food, animal feed and bioenergy production. It is also planted as a forage crop for livestock and the straw can be used as a ruminant feed component or construction material [12].
