The Impact of Anthropogenic Climate Change on Egyptian Livestock Production

Simple Summary Egypt is one of the hottest countries on the planet, with significant warming predicted to occur over the course of this century. It has a substantial livestock population to feed its growing human population, but the hotter temperatures will constrain the production of ruminants in particular because of their high internal heat production during the digestion of fibrous material by micro-organisms. The net result will be the diminished availability of animal products per human member of the Egyptian population. Some products can be imported, but this is difficult for products with a short shelf life, such as milk. We use estimates of climate change, population growth and the impact of higher temperatures on cow productivity to predict that milk availability per person will decline from 61 kg/year in 2011 to 26 kg/year in 2064. We discuss the range of alternative options available to make up for diminished animal product availability per person as the century progresses. Abstract Egypt is one of the hottest countries in the world, and extreme climate events are becoming more frequent, which is consistent with the warming of the planet. The impact of this warming on ecosystems is severe, including on livestock production systems. Under Egyptian conditions, livestock already suffer heat stress periods in summer. The predicted increases in temperature as result of climate change will affect livestock production by reducing growth and milk production because of appetite suppression and conception rate reductions and will increase animal welfare concerns. In severe cases, these effects can result in death. We review the heat stress effects on livestock behaviour, reproduction, and production in the context of predicted climate change for Egypt over the course of this century and offer alternative scenarios to achieve food security for a growing human population. As an example, we combine predictions for reduced milk production during heat stress and human population trajectories to predict that milk availability per person will decline from 61 kg/year in 2011 to 26 kg/year in 2064. Mitigation strategies are discussed and include the substitution of animal-based foods for plant-based foods and laboratory-grown animal products.


Introduction
The climate of a region is its typical or average weather pattern, and we adopt the climate change definition of being "attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods" [1]. This is not an entirely new phenomenon-the average surface temperature of the planet increased by about 1.1 • C in the 19th century. However, climatic extremes have recently increased in both magnitude and frequency [2][3][4][5], with further increases projected in the future [6][7][8].
Mediterranean ecological systems, including the agriculture and water cycles, are being drastically affected by climate change [9], with harmful effects on animal welfare and production, which are expected to increase in the future [10,11]. Egypt has a precarious economy, which depends, in part, on livestock production for income and food security.

Climate Profile of Egypt
For at least the last decade, it has been acknowledged that Egypt is one of the countries that is the most exposed to climate change [25], which is largely due to the extent to which it relies on natural resources. It has been estimated that it is the fifteenth most vulnerable country to human-induced environmental change [26]. Climate change in Egypt is already evident in the form of lower precipitation rates, changing weather patterns, increased CO 2 in the atmosphere, methane and nitrous emissions, and sea level rise [18].
The Egyptian climate is characterized by warm days and cold nights. There are two main seasons: a mild winter (November-April) and a hot summer (May-October). The average temperature range in the coastal regions is between a 14 • C minimum in winter and a 30 • C maximum in summer. In the desert areas, the temperatures reaches 7 • C at night and 43 • C during the day in summer, while in winter, temperatures are as low as 0 • C at night and 18 • C during the day [27]. The annual mean air temperatures range from 20-22 • C in coastal region to [28][29][30] • C in the south-eastern corner [27].
A Global Rice Science Partnership report [28] compared two periods, from 1901-1950 and from 1951-2016. The report highlighted increases in the maximum temperature, about 0.6 • C and 0.4 • C in winter and summer, respectively, in lower Egypt, which was considered to be primarily due to the growth in urbanization in that region. The minimum temperature increases seen in winter ranged from 0.85 • C in Cairo to 0.50 • C in southern Egypt, and in summer, the increase seen in southern Egypt was 0.7 • C, while in the north, the increase was 0.45 • C. This temperature reversal between the two zones in the two seasons may be due to heat retention in the desert in the south in summer as well as to an absence of wind and rain.
The annual current average temperatures are 20 • C on the Mediterranean coast, 24 • C on the Red Sea coast, 25 • C in Cairo, and 26 • C in Aswan in the south [29]. The typical maximum temperatures for daytime in midsummer range from 30 • C in Alexandria on the Mediterranean coast to 41 • C in Aswan in the far south, while daytime midwinter maximum temperatures are 18 • -23 • C. There was greater warming in summer (0.31 • C/decade) than in winter (0.07 • C/decade) between 1960 and 2003 [29].
Solar radiation (4500 KJ/m 2 ) is high during the entire year for all Egyptian zones, with extremes during the summer season and high humidity (50-75%) in the coastal region and low humidity in the very dry desert areas [30]. Farm animals experience climate stress for about 6 months of the year, causing various physiological and biochemical changes due to the increased heat production and reduced heat loss, manifesting in impaired health, production, and reproduction [31,32].

Climate Change Estimates for Egypt
Early this century, the IPCC predicted a 1.4 to 5.8 • C increase in the average global surface temperature over the course of the 21st century [33]. The Second National Communication (SNC) to the United Nations Framework Convention on Climate Change (UNFCCC) reported that, "Egypt is one of the most vulnerable countries to the potential impacts and risks of climate change" [34]. Climate extremes have occurred frequently during the first decade of this millennium, with estimates of increasing intensity due to climate change. Overall, Mediterranean Africa is likely to be warmer and drier [35].
The anticipated average temperature increase due to global warming is 4 • C for Cairo and 3.1-4.7 • C for other areas of Egypt by 2060 [36]. Temperature change estimations from the records of 11 meteorological stations distributed around the country during the 1960 to 2005 period [27] show that the mean annual temperature increased by 2.1 • C. A warming trend was detected throughout the whole country. Using estimates for the period from 1976 to 2005, an increase in both the daily maximum and minimum temperature has been detected [27]. During the period from 2006-2015, the average maximum temperature increase was from 1.4 to 2.6 • C, while the minimum temperature increase was between 1.2-1.8 • C [8].
One of the most severe heat waves in the Mediterranean area was in June and July 2007 [37], with temperatures reaching 45 • C in northern Egypt [38]. A heat wave is a period of prolonged excessively hot weather that is associated with increased humidity in coastal areas. It is measured in relation to the normal weather of the area and the normal temperature of the season. Heat waves are formed when barometric pressure increases above 3000-7600 m [39] and when it remains high for several days/weeks, which is common in the summer season. In summer, changes in the weather pattern occur more slowly than they do in winter; hence, the high pressure moves away more slowly. Under this high pressure, hot air sinks toward the surface, leading to warming and drying. This warm sinking air inhibits convection, trapping warm humid air underneath, which results in a continuous heat build-up at the surface that is experienced as a heat wave [40]. There have been 12 heat wave occurrences between 1981 and 2012 in Damietta, Egypt [40].
Observations from the Mediterranean and Middle East regions between 1950 and 2000 indicate that these regions warmed faster from June to August than the global average temperature [41]. Therefore, projected temperature increases are likely to be greater in Egypt than they are globally. Over the whole of North Africa, both annual minimum and maximum temperatures are likely to rise in the future, especially the minimum temperature [42].
In Egypt, between 1960 and 2010, the maximum and minimum temperatures increased at rates of 0.27 ± 0.03 and 0.30 ± 0.07 • C/decade, respectively. In the period from 1980 to 2017, this rate increased to 0.40 ± 0.1 • C/decade, indicating an acceleration of the warming [8]. The IPCC expect that the sea level will rise by 0.5-1 m by 2100 [43], and the IPCC Fifth Assessment Report predicted an increase in the global average surface temperature of between 0.3 and 4.8 • C by 2100 [44]. Climate change projections expect a temperature increase over Egypt of about 3-3.5 • C and over the Middle East region in general [29]. Additionally, it is predicted that the average annual temperature in Egypt will increase by 1.07-1.27 • C by 2030, with a 10th percentile of 0.37-0.61 • C and a 90th percentile of 1.78-2.11 • C [45]. The projected increase in the maximum temperature is predicted to be 1.00-1.22 • C, and the minimum temperature increase is anticipated to be 1.09-1.32 • C. By 2050 (2040-2059), the mean annual temperature will increase by 1.64-2.33 • C, with a 10th percentile of 0.81-1.52 • C and a 90th percentile of 2.62-3.45 • C [45]. This increase is expected to be greater in summer, and the number of hot days will increase, and the number of cool days decrease. Tables 1 and 2 give the predicted temperature increases from 2025 to 2100 for high and low emission scenarios [46,47]. Nashwan et al. [48] predicted increases in the maximum (1.80-3.48 • C) and minimum (1.88-3.49 • C) temperatures in the Central North region of Egypt (CNE) by the end of the century. In addition, they anticipated that the annual temperature will increase by an average of 5.6 • C between 1990 and 2100 under a high emissions scenario, with more warm days, increasing from less than 10 days in 1990 to 195 days in 2100. If there are decreased emissions, the temperature increase will be limited to 1.6 • C, and the warm days will be limited to 45 days [49].
Mostafa et al. [8] predicted temperature increases of between 0.28 ± 0.04 • C/decade and 0.38 ± 0.09 • C/decade between 2010-2040 but higher temperature increases between 2050 and 2100, from 0.48 ± 0.18 • C to 0.72 ± 0.11 • C/decade. When compared to the period of 2006-2015, they predicted more frequent hot days and nights, which will occur at a higher rate near the Red Sea and in upper Egypt sites than they will in other areas. In the last decade, 80% of the days/year were hotter than 90% of days in the reference period of 2006-2015. Additionally, in comparison with the reference period from 1986-2005, the temperature increase will be between 0.3-4.8 • C in 2081-2100. For 2090, it was projected that the maximum temperature will be between 2.0 ± 0.6 • C and 5.6 ±0.5 • C above that of 2006-2015 values.
In 2007, the Egyptian Ministry of Water Resources and Irrigation climate change adaptation strategy [50] anticipated that the temperature will increase 1 • C by 2025, which appears likely to be true; similarly, the potential impact of climate change on the Egyptian economy report [51] anticipated an increase between 0.9 and 1 • C by 2030.

Climate Change Impacts on Livestock Production in Egypt
Livestock production contributes significantly to the national economy of the countries of the Near East and North Africa region, with increases from 186 million to 412 million head over the 40 years until 2010 [52]. Livestock production represents 24.5% of the agricultural Gross Domestic Product (GDP) [53,54]. In 1999, livestock production had contributed 27% of domestic agricultural production [55]. The main livestock production in Egypt is by small-scale farmers, with government farms contributing to less than 2% of the production [54]. Egyptian animal production depends on water buffaloes (70%) and cattle (30%) for annual milk-production and using males and barren females for meat production [56]. The buffalo population increased from 3,250,000 head in 1993 to 4,200,000 head in 2013 [57] due to an increased demand for buffalo products such as milk, cheese, and butter. However, the numbers of buffaloes and cattle have also been estimated as 3.5 and 5.01 million head, respectively, in 2016 [58]. In 2016, the buffalo herd contained 42% dairy buffalo cows, 32% buffalo heifers, 6% bulls, and 20% male calves.
In 2016, poultry meat production in Egypt was about 148,517 metric tons, which exceeded all other livestock meats, including beef and veal, buffalo meat, sheep and goat meat, camel meat, and others. Calf (buffalo and cattle) production increased to 1.93 million head in 2018 from 1.85 million head in 2017 [17]. A similar pattern of poultry dominance has been seen in other countries in the region. In Algeria, chicken production was 137,235 metric tons in 2016, increasing to 138,500 in 2019. At the same time, cattle production, which was from 2,081,306 head in 2016 dropped to 1,780,591 head in 2019. In Tunisia, chicken production was 90,742 metric tons in 2016, increasing to 92,663 metric tons in 2019, while the cattle population was 646,100 head in 2016, increasing to 653,611 head by 2018. In Syria, chicken production was 16,600 metric tons in 2016, increasing to 18,498 in 2019; cattle production was 1,090,000 head in 2016, decreasing to 788,321 head in 2019 [57].
In 2017, the human population was about 104 million, with 56.7% living in rural areas and 43.3% living in urban areas [58]. By 2020, the population had reached 120 million, with the growth rate anticipated to be unchanged. It is expected to increase to 151 million in 2050, with the urban share becoming 56.5% [59]. Although livestock numbers in the last 20 years have increased, this increase is not adequate for the requirements of the increased population, especially in terms of dairy products. Only in the poultry sector has a steady increase in numbers been evident, increasing by about 4% per year [58], which is more than sufficient to cater for the annual human population increase of 1.9%, but this growth may not be sustainable in the future. Numbers of ruminant livestock have declined, and a decrease of about 10% has been seen in sheep and buffalo since about a decade ago, which is probably due to the pressure of urbanization, drought, and diminishing feedstocks. Livestock production (principally from cattle, buffalo, sheep and goats, and camels) contributes to about 37.5% of agriculture production [60].
Livestock production and health is challenged both directly and indirectly by climate change. With higher temperatures, livestock health and production are challenged by heat stress, metabolic disorders, oxidative stress, and immune suppression, together with an increased incidence of diseases. The indirect effects are related to the multiplication and distribution of parasites and infectious pathogens and the impact on feed availability [61]. The direct impact of climate change on livestock is influenced by the ability of animals to exchange heat with their environment [53]. If animals lack the ability to dissipate envi-ronmental heat, they suffer from heat stress. There are various detrimental effects of heat stress on livestock, with the most important economic impact being on reproduction and milk production in dairy cows. Heat stress has a direct adverse effect on milk production, growth, feed intake, reproductive efficiency, and disease incidence in dairy cows [62]. When the environmental temperature rises above the thermal comfort zone, it adversely affects the growth and productivity of animals in both intensive and extensive production systems. In addition to the reduction in milk production, it leads to a reduction in sperm quantity and quality and a decline in female fertility and embryo quality.
Heat stress also decreases the body weight of beef cattle due to decreased feed intake and feed conversion efficiency [17]. Additionally, dairy cattle in heat stress have a particular stance, with a lowered head, backward-facing ears, and a vertical tail [63]. An increase in the ambient temperature could also reduce forage digestibility in ruminants because of the greater lignification of the plant [64]. A negative correlation has been found between ambient temperature and degradability, in which the potential degradability of plants was decreased in tropical and arid climates by 0.55% compared to cold and temperate climates, for each 1 • C increase in ambient temperature.
Farm animals have behavioural strategies to attempt to mitigate the impact of heat stress. Birds respond to heat stress by extending their wings, holding them away from their body, increasing their respiration rate, which has the potential of leading to exhaustion, in an attempt to reduce the heat load through water vapor cooling. Other strategies include looking for isolated places to lower their body temperature, moving away from each other, less activity, decreasing feed intake, and increasing water consumption [65]. The negative effects of climate change on poultry production are mostly direct, reducing weight gain and meat quality in broilers and the rate of egg production, egg quality (especially thin and breakable eggshells), egg weight and size, and a high mortality rate in laying hens [65]. There are also indirect effects reducing growth and reproduction, in particular through the enhanced growth of toxin-producing fungi in feed or by reducing the bird's ability to cope with other stressors. Moreover, immunity is reduced in birds exposed to heat stress, including a weak immune response to vaccines, which lowers the birds' resistance to infectious diseases.
A temperature increase of 1 • C above the ideal temperature leads to a reduction in the feed consumption of laying hens by 1.6%, while the amount of energy consumed reduces by about 2.3% [65]. The egg weight also decreases at rate of 0.07-0.98 g/egg for every 1 • C rise, which can be attributed to the decrease in calcium availability because of the reduction in the food consumption. When temperatures increase to above 30 • C, feed consumption and egg production reduce by 5% and 1.5%, respectively. Approximately one half of this reduction in food consumption occurs when the temperature is elevated from 21 to 38 • C.

Climate Change Effects on Milk Production
More than 50% of cattle population is present in the tropics, which explains why heat stress will cause a substantial economic loss in dairy farm profitability around the world [66,67]. At temperatures between 10 and 30 • C, most livestock species perform well. Above this, a reduction in milk yield and feed intake occur in cattle [68][69][70], as, when the rectal temperature of dairy cows exceeds 39.4 • C, the cows need more energy for the maintenance of their body temperature at the expense of energy needed for milk production [71]. Additionally, as previously described, temperatures above 35 • C activate the thermal stress regulatory mechanisms to reduce feed intake, leading to a negative energy balance that affects milk synthesis [72,73].
Every unit increase above a temperature-humidity index (THI) value of 71 reduces milk yield by 0.2 kg/day in dairy cows that have no access to shade [71,74,75]. When over 78, milk production also declines in those having access to both shade and sprinklers. In the Mediterranean climate, other researchers have estimated that every unit increase in the THI above 69 reduces milk production by 0.41 kg per cow per day [76,77], but the reduction will depend on the physiological state of the animals and the environment. In farms without sprinklers or other heat mitigating measures, milk yield can decline by 40-50% under heat stress, while in cooled farms, it may only be 10-15% [74,78]. This can mainly be attributed to decreased nutrient intake [77], but Ernabucci and Calamari reported that the reduction in milk yield ranges from 10 to >25%, half of which is due to the reduction in feed intake and the remaining half to heat-related lactogenic hormone reduction [79]. The decrease in milk production is particularly affected by the cow's breed, age, stage of lactation, and forage availability. An elevated core body temperature not only reduces milk output but also reduces milk protein, fat and lactose percentages in milk, and colostrum [80][81][82]. Furthermore, calcium (Ca), phosphorus (P), and magnesium (Mg) content are reduced in milk, and chloride is increased [83]. There is a reduction in milk short and medium chain (C4-C10, and C12-C16, respectively) fatty acids and an increase in long-chain fatty acids (C17-C18) [83]. This is due to a reduction in their synthesis in the mammary glands and energy being used by the cow to cope with the heat stress. Moreover, αand β-casein and P in milk are reduced, and the pH increases [84].
Heat stress affects prolactin, thyroid hormones, glucocorticoids, growth hormone, estrogen, progesterone, and oxytocin levels, all of which are involved in the control of milk production. In addition, mammary gland involution during the dry period is retarded by heat stress, leading to apoptosis, autophagy, and decreased epithelial cells [82]. Furthermore, heat stress can lead to immunosuppression, with an increase in somatic cell count and more disease in dairy cattle [85]. The mammary gland uses a negative feedback mechanism to reduce milk production [20,86], and if the udder temperature increases, it can also lead to mastitis [87]. Colostrum and IgG transfer to colostrum are also reduced when heat stress occurs near calving time [74,88].
Genetic improvement for increasing milk production is linked to greater feed intake, which makes high yielding cows more sensitive to heat stress than low yielding ones. For high yielding cows, the upper limit of the thermoneutral zone is moved to a lower temperature [89].
We reviewed 18 published temperature increase estimates in Egypt (Table 3), which were, on average, from a mean reference year of 2011 over a period of 56.4 years to a mean year of prediction of 2067. Over that same period, the Egyptian population is forecast to increase from 84,529,251 in 2011 to 189,463,934 in 2067 [58]. The temperature -humidity index was calculated for the prediction years. Assuming a conservative 0.21% milk yield reduction per unit of THI increase over 68 [76], we then calculated the THI for the prediction year -68 and the reduction in milk yield per cow per year at the higher temperature in the year of prediction. This showed that on average, there would be a 3.88% reduction in milk production per cow over the 56.4 years of our survey. We then calculated mean milk consumption per head of the population in Egypt  The options to maintain milk consumption are to (1) increase the national herd size by a factor of 2.64, i.e., from 4.95 million to 13.07 million, keeping the production per cow the same, or (2) to increase production per cow by a similar proportion. Alternatively, milk imports could be increased, or alternative, plant-based milks could be manufactured in Egypt or imported from outside. Table 3. Review of predictions of increased temperature in Egypt, temperature-humidity index (THI), and reduction in total milk yield (TMY) per cow and available milk yield per person.

Egypt's Proposed Mitigation and Adaptation Actions
A decade ago, Egypt announced a national strategy for adaptation to climate change and disaster risk reduction [90], which had three main components: 1. increasing the flexibility of the Egyptian community in dealing with the risks and disasters caused by climate change and its impact on different sectors; 2. enhancing the capacity to absorb and contain climate-related risks and disasters; 3. reduction of climate change-related disasters.
In Egypt's Third National Communication in 2016 [27], the overall goal of the Egyptian national strategies and programs was to increase livestock production by adaptation to climate change. This addresses both criteria 1 and 2 listed above. It was anticipated that this could be achieved by matching stocking density increases with greater crop production, rotating pastures, modifying grazing times to cooler periods of the day, altering forage and animal species/breeds, and altering the integration of livestock/crop systems, including the use of adapted forage, increased fertilizer application, ensuring an adequate water supply, and the better use of supplementary feeds. It was also intended to improve lowproductivity cattle through better feeding programs, enteric fermentation, and manure management [91]. However, biological limits to these factors may already have been reached; hence, other options must be considered.
Other possibilities include environmental modification through the use of technology to prevent solar heat loads and increasing opportunities for animal heat loss through using shelter and cooling systems; also, nutritional options, such as fibrolytic enzyme supplementation, could be used. Supplementation with exogenous cellulolytic enzymes in ruminant diets can improve the digestibility and feeding value [92]. Ruminants could be supplemented with rice straw and grains inoculated with fungal and bacterial strains to improve digestibility and to reduce methane production. Additionally, more sustainable by-products and novel feeds could be used; including the potential use of tree forages to increase the growth performance of livestock, contributing to food security [93]. However, the selection of the best fodder tree species is important because of the association between the tannin content of fodders with enteric fermentation efficiency and its contribution to climate change mitigation. Paulownia leaves are particularly rich in crude protein, essential amino acids, and phenolic substances [94]. Therefore, supplementation with Paulownia hybrid leaves and ensiled Paulownia hybrid leaves could potentially mitigate methane production and could improve ruminal fermentation. Additionally, they may serve as valuable components in ruminant diets to increase nutrient and energy supply in particular, as well as potentially improving the fatty acid profile of milk.
Animal selection and breeding must take into account the conflict between those favouring adapted indigenous, low-producing animals and those favouring exogenous high-producing, less tolerant animals. Following the latter strategy will require increased grain feeding at a time when the human population is growing and when food security is therefore declining [95]. Livestock can adapt themselves to low quality crop residues such as straws and stubbles. Therefore, there is an advantageous use for fodder trees, shrubs, and cacti [96]. In ruminant diets that contain triticale and oats as the sole grain sources, a partial replacement for true protein (e.g., soybean meal) with feed-grade urea as a source of nonprotein nitrogen may result in an improvement in microbial protein synthesis in the rumen, minimizing N excretion to the environment [97]. Treating triticale and oat grains with urea can modulate ruminal microbiota and fermentation beneficially, consequently improving production performance and profitability [98].
The development of low-cost feed options, "feed blocks", that consist of multiple cheap, easily available agro-industrial by-products, such as tomato pulp, molasses, burghul derivatives, crude olive cake, sesame cake, citrus pulp, sunflower cake, and mulberry leaves, will help reduce reliance on grains. Different combinations have been tested in Syria, Iraq, and Tunisia. For example, replacing part of the barley grain component of the diet with molasses and urea in combination with urea-treated straw for feeding ewes improved the reproduction of the ewes, who could be mated earlier, giving birth at shorter intervals, and producing lambs that were heavier at weaning, as a result of increased milk production [99]. These alternative agro-byproducts and ammoniated straws are considered options for poor farmers in the Middle Eastern region to increase their livestock productivity and income without affecting the quality of the products [100].
As ruminants contribute to the predicted temperature increases through greenhouse gases (GHGs), there is pressure to reduce these by improved feeding management, more efficient enteric fermentation, and, in particular, reduced methane emissions. A higher proportion of concentrate can result in a methane emission reduction, and methane emission reduction from enteric fermentation can be achieved by feeding diets containing feed additives, antibiotics, or vaccines. Additionally, good pasture management through rotational grazing is considered an effective way to reduce GHG emissions [101]. Ruminants fed on high fibre and low protein diets produce more methane than those fed on good quality forages or those supplemented with concentrate feed [102]. Therefore, adjusting animal diets can reduce GHG emissions through the better matching of their nutritional requirements with less methane production.
In addition to the biotechnological options, such as the greater use of artificial insemination (AI), embryo transfer (ET), in vitro fertilization (IVF), and sexing and cloning, molecular biotechnology could revolutionise animal health and production using DNAbased applications and enhanced vaccination programs, e.g., against avian flu. In the same context, the feed production gap can be closed through these adaptation options: (i) avoiding feeding berseem clover alone and combining it with lower protein feeds, e.g., grass silage, to avoid wasting protein, which also has a significant detoxification cost in ruminant livestock, (ii) rangeland improvement, (iii) crop residue use, (iv) hydroponic barley feeding, (v) saline water utilization for crop production, and (vi) better livestock integration into the arable farming systems to utilize manure better. If these are not successful, the Egyptian population must rely on alternative strategies to achieve food security, such as plant-based proteins and meat grown in laboratories in vitro. These could be produced more efficiently, depending on whether livestock rely on by-products with no other use. The high cost of in vitro meat production is currently a barrier to widespread adoption [27].

Conclusions
Livestock production in Egypt is likely to face severe challenges if the predicted temperature changes occur later this century, as seems likely from recent experience. As one of the hottest countries on the earth and as a country with a rapidly growing human population, heat stress will become the major constraint on animal production unless there is appropriate mitigation. Mitigation options are available but are expensive to implement and do not seem compatible with the growing needs of the human population for safe, affordable food. Alternative high-value foods, such as clean meat and processed plant proteins will therefore need to be introduced to achieve food security. This will require the re-education of the Egyptian population about the value of alternatives to livestock in their diet and the provision of assistance for Egyptian livestock farmers who are willing to convert to more efficient methods of producing food for a secure future for Egyptians. As ruminants contribute to the predicted temperature increases, a reduction in ruminant livestock use for food production could reduce the anticipated temperature changes.