Dr. J. Abraham
Consultant Meat Technologist
The issue of climate change is increasingly receiving attention from scientists, the public, and policymakers. The United Nations (UN) Convention on Climate Change defines climate change as “a change of climate which is 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”. According to general consensus, the global climate is changing, which may also affect agricultural and livestock production in the world. The potential impact of climate change on food security is a widely debated and investigated issue. Nonetheless, the specific impact on the safety of food for consumers has remained a less studied topic. The major issues identified are the presence of pathogenic bacteria in foods following more frequent extreme weather conditions, such as flooding and heatwaves, toxins formed on livestock products during storage; residues of pesticides in products affected by changes in pest pressure, etc.
Livestock systems in developing countries are changing rapidly in response to a variety of drivers. Livestock products are an important agricultural commodity for global food security because they provide 17% of global kilocalorie consumption and 33% of global protein consumption. The livestock sector accounts for 40% of the world’s agricultural gross domestic product (GDP). It employs 1.3 billion people and creates livelihoods for 1 billion of the population living in poverty. Climate change is seen as a major threat to the survival of many species and ecosystems, and the sustainability of livestock production systems in many parts of the world. There is a growing demand for livestock products, and its rapid growth in developing countries has been deemed the ‘‘livestock revolution”.
Increased ambient temperature is one of the most exacerbating attribute imposing severe consequences on livestock production. Heat stressed animals reduces feed intake and water intake. This can alter the endocrine profile thereby increasing the maintenance requirements which leads to reduced production performance of animals. Industrialized farming systems are less affected by climate change than livestock systems based on grazing and mixed farming systems. Meat and milk production is found to be decreased more in the grazing based livestock systems and this could be attributed to less foraging of animals as they try to remain in the shade during hot weather conditions (Inter-governmental Panel on Climate Change – IPCC, 2013).
Milk production was found to be reduced during heat stress and high producing animals are more affected than the low producing animals. Further, beef cattle with heavier hair coat and darker coat colour are very sensitive to heat stress. Heat stress affects the meat quality by increasing the pH of the meat and decreasing the Warner–Bratzler shear force and darker meat. Heat stress greatly affects the poultry industry through consequences on carcass weight, body weight, carcass protein, muscle calorie, drip loss, and shear force of breast muscle.
Apart from getting affected by the ever-changing climate, livestock is also an important contributor to the phenomenon. Both these pathways need to be targeted to improve sheep production in the changing climate scenario. This warrants efforts simultaneously to reduce the GHG emission from sheep apart from targeting reducing the impact of climate change. Only such efforts can help to sustain sheep production in the changing climate scenario.
Impact of climate change on livestock Population
Despite uncertainties in climate variability, the IPCC Fifth Assessment Report identified the increase in global average surface temperature by 2100, which is between 0.3 ºC and 4.8 ºC (IPCC, 2013). The potential impacts on livestock include changes in production and quality of feed crop and forage, water availability, animal growth, meat and milk production, diseases, reproduction, and biodiversity. These impacts are primarily due to an increase in temperature and atmospheric carbon dioxide (CO2) concentration, precipitation variation, and a combination of these factors. Temperature affects most of the critical factors for livestock production, such as water availability, animal production, reproduction, and health. Forage quantity and quality are affected by a combination of increases in temperature, CO2, and precipitation variation. Livestock diseases are mainly affected by an increase in temperature and precipitation variation.
Effect of Heat stress on livestock
All animals have a thermal comfort zone, which is a range of ambient environmental temperatures that are beneficial to physiological functions. During the day, livestock keeps a body temperature within a range of ±0.5 ºC. When temperature increases more than the upper critical temperature of the range (varies by species type), the animals begin to suffer heat stress. Animals have developed a phenotypic response to a single source of stress such as heat called acclimation. Acclimation results in reduced feed intake, increased water intake and altered physiological functions such as reproductive and productive efficiency, and a change in respiration rate.
Heat stress on livestock is dependent on temperature, humidity, species, genetic potential, life stage, and nutritional status. Livestock in higher latitudes will be more affected by the increase of temperatures than livestock located in lower latitudes because livestock in lower latitudes is usually better adapted to high temperatures and droughts. Heat stress decreases forage intake, milk production, the efficiency of feed conversion, and performance. Warm and humid conditions cause heat stress, which affects behavior and metabolic variations on livestock or even mortality. Heat stress impacts on livestock can be categorized into feed nutrient utilization, feed intake, animal production, reproduction, health, and mortality.
Climate Change Impact on Meat Industry
Significant research has been done on heat stress impacts on meat quality and composition especially in cattle, sheep, goat, pig, and broilers. High temperature and humidity result in increased meat pH, less expressed juice, cooking loss, and drip loss. During exposure to high temperatures, the energy utilization gets decreased while the energy expenditure is increased for thermoregulation. This deteriorates the quality of the meat by decreasing the muscle glycogen leading to an increase in muscle pH. The functional properties of meat such as color, water holding capacity (WHC), and myofibrillar fragmentation index (MFI) were also negatively influenced during heat stress in ruminants. Further, animal management practices during climate change also can indirectly affect meat quality. For example, rearing heat-tolerant Bos indicus cattle is an effective adaptation strategy against the prevailing harsh climatic conditions. This can lead to tougher and less juicy beef. Besides the qualitative alterations driven by the heat load on the animals, carcass weight losses in heat-stressed animals also have economic significance.
Ante-mortem temperature stress is a major determinant for live carcass weight losses, hot carcass weight, and retail meat yield. Energy partitioning for thermoregulation accompanied by reduced feed intake to reduce heat load resulted in live weight losses. From these findings, it is evident that heat stress declines both qualitative and quantitative characteristics of meat. However, these adverse effects of heat stress on meat quality is variable based on the region of animal origin. This warrants developing region-specific appropriate strategies to cope up with heat stress to improve meat production in the changing climate scenario.
Food Safety and Climate Change
The impact of climate change will not be even across different food systems. Some regions are projected to have an increase in food production; however, generally, the projected climate change is foreseen to have a negative impact on food security, especially in developing countries. The effects of climate change on food security and consequently nutrition are closely linked to effects on food safety and public health and must be considered together. Climate change is expected to lead to modified bacterial, viral, and pathogenic contamination of water and food by altering the features of survival and transmission patterns through changing weather characteristics, such as temperature and humidity. Climate-dependent temperature and moisture, fungal growth, and formation of mycotoxins will lead to changes in occurrence patterns. Mycotoxins are produced by certain fungi (moulds) on crops and can cause both acute toxic effects and chronic health problems (including cancer) in humans and livestock. Climate change has also been described as a ‘catalyst for the global expansion’ of algal blooms in oceans and lakes, interacting with nutrient loading from fertilizer run-off into water bodies.
This high risk of emerging zoonoses, changes in the survival of pathogens, and alterations of vector-borne diseases and parasites in animals may necessitate the increased use of veterinary drugs, possibly resulting in increased residue levels of veterinary drugs in foods of animal origin. This poses not only acute and chronic risks to human health but is directly linked to an increase in antimicrobial resistance (AMR) in human and animal pathogens. The application of pesticides, and the subsequent residues in food, is an ongoing concern that is expected to become more prevalent due to climatic changes, with shifts in farming systems and farmers’ behavior to adapt to the changing climate. Climate change increases the frequency and severity of extreme weather events which impacts food security. Where food supplies are insecure, people tend to shift to less healthy diets and consume more “unsafe foods” – in which chemical, microbiological and other hazards pose health risks and which contribute to increased malnutrition.
Food safety: how climate change impacts our food
Food and feed micro-organisms
Climate change has been identified as having the potential for increased bacterial contamination of food and water, which consequently may result in a change of risks related to water- and foodborne infection diseases. Water- and food-borne bacteria can cause mild to serious human gastrointestinal disease and in part severe complicating problems such as hemorrhagic colitis or hemolytic-uremic syndrome (Escherichia coli O157:H7), Guillain-Barré syndrome (Campylobacter spp.,) and meningitis (Listeria monocytogenes). Although it is possible to establish correlations between meteorological parameters and the behavior of bacterial food pathogens in some cases, it is at present not yet possible to fully predict water- and food-borne bacteriosis caused by climate changes.
The problem of bacterial pathogens is complicated by the fact that many of these organisms can survive for long periods and multiply in the environment. For example, the pathogenic water and food-borne bacteria E. coli O157:H7, L. monocytogenes, Salmonella spp. and Campylobacter spp. are able to persist for extended periods in the environment. Climate change is expected to lead to increased bacterial, viral, and pathogenic contamination of water and food by altering the features of survival and transmission patterns through changing weather characteristics, such as temperature and humidity. Even increased contamination of the water used for irrigation can impact upon the safety of crops, and animals who consume the crops, and their resulting food output. The production of food itself may also be directly affected by climate change through the alteration of survival and/or multiplication rates of some food-borne pathogens. For example, the multiplication of Salmonella spp., a major contributor to foodborne disease, estimated to be responsible for over 50,000 deaths in 2010, is strongly temperature-dependent. An increase in temperature, or the duration of high-temperature episodes in particular geographical areas, may provide better conditions for the multiplication of Salmonella spp. in foodstuffs.
As cited by WHO in the 2017 report on protecting health in Europe from climate change, cases of salmonellosis increase by 5-10% for each 1°C increase in weekly temperature when ambient temperatures are above 5°C. In the same report, citing a study in Kazakhstan, there was a 5.5% increase in the incidence of salmonellosis with a 1 °C increase in the mean monthly temperature. Another major source of foodborne disease, Vibrio cholerae is estimated to cause over 760,000 illnesses and 24,000 deaths every year. It is commonly associated with the consumption of contaminated water filtrating organisms, such as mussels and clams. Climate change has been described as a promoter for the global expansion of algal blooms that contaminate these water filtrating organisms.
Mycotoxins and phycotoxins
Mycotoxins are compounds naturally produced by a large variety of fungi (moulds) that can cause acute effects, including death, along with chronic illnesses from long-term exposure, including various forms of cancer. It has been estimated that 25% of the world’s yearly crop production is contaminated with mycotoxins. Mycotoxins are known to occur more frequently in areas with a hot and humid climate. Mycotoxins can be produced before harvest in the standing crop and many can increase dramatically, even after harvest if the post-harvest conditions are favorable for further fungal growth. Human dietary exposure to mycotoxins can occur either directly, through the consumption of contaminated crops or indirectly, through the consumption of animal-derived foods from livestock that have consumed contaminated feed. It has been estimated that an increase of one degree in global mean temperature will reduce average global yields of wheat by six percent. This decrease in food availability can result in an increased risk to public health from mycotoxin intoxication, in particular in (developing) countries where small-scale farmers and families sell locally and eat what they grow, thereby being forced to sell and consume contaminated crops to survive.
A number of algae produce toxic compounds, the so-called phycotoxins that exert adverse effects on human consumers of seafood containing these toxins. For example, water-filtrating organisms, such as mussels and clams, are prone to contamination with these toxins. The symptoms that these toxins may cause after consumption are, for example, Paralytic Shellfish Poisoning and Diarrheic Shellfish Poisoning. Ciguatera fish poisoning (CFP) is a pantropical illness caused by the bioconcentration of algal toxins, known as ciguatoxins (CTXs), in marine food webs. Ciguatera fish poisoning is among the world’s most common seafood-toxin diseases. Growth, distribution, and abundance of CFP-associated dinoflagellates are largely temperature driven and expected to shift in response to climate-induced changes as ocean temperatures rise. This can be observed in the geographic regions in which CFP outbreaks have been reported, which appear to have been expanding geographically over the last two decades.
Zoonosis and other animal diseases
Outbreaks of zoonotic diseases, those that are transmissible from animals to humans, will increase during periods of warmer weather and droughts, with a significant impact upon public health. The changing weather patterns are expected to alter the survival of pathogens in the environment, changes in migration pathways, carriers and vectors, and changes in the natural ecosystems, all of which will contribute to outbreaks and spread of zoonotic diseases. While in the aquaculture sector, a warming of the environment and oceans will lead to disease organisms thriving, which may result in increased incidences of mass fish deaths, or an increase in the use, and potential for misuse, of chemicals to control diseases, leading to the possibility of increased residues in fish and seafood products, subsequently impacting public health.
The high risk of emerging zoonoses, changes in the survival of pathogens, and alterations of vector-borne diseases and parasites in animals may necessitate the increased use of veterinary drugs to combat the increasing challenges faced by farmers. This may subsequently result in an increase in residue levels of veterinary drugs in foods of animal origin, with possibly harmful effects on public health. Increased residue levels of veterinary drugs in foods of animal origin pose not only acute and chronic risks to human health but are directly linked to an increase in antimicrobial resistance (AMR) in human and animal pathogens. With the increasing frequency of antibiotic-resistant diseases and bacteria, humans are becoming more susceptible, with climate change and its effects on human behavior contributing to this susceptibility.
Pesticides and pesticide residues
The application of pesticides, and the possibility of subsequent residues in food, is an ongoing concern that is expected to become more prevalent due to climatic changes, with shifts in farming systems and farmer behavior to adapt to the changing climate. For example, changes in mean and extreme temperatures and rainfall patterns make it likely that crops will be grown in different zones of cultivation, with a subsequent attraction of different pests, diseases, and weeds. Furthermore higher moisture and higher temperature will increase the pressure from pests, and result in an altered weed flora, which is expected to increase the need for pesticides. In response, pesticide use patterns will likely change. It is anticipated that such changing patterns will result in a higher risk of elevated exposures of humans to pesticides via residues in food.
Climate change will affect livestock production and consequently food security. Livestock production will be negatively impacted (due to diseases, water availability, etc.), especially in arid and semiarid regions. In addition, climate change will affect the nutritional content of livestock products, which are one of the suppliers of global calories, proteins, and essential micronutrients. Under the climate change scenario, elevated temperature and relative humidity will definitely impose heat stress on all the species of livestock, and will adversely affect their production and reproduction. The immediate need for livestock researchers aiming to counter heat stress impact on livestock production is to understand the biology of heat stress response components in deep and measures of animal well-being, giving researchers a basis for predicting when an animal is under stress or distress and in need of attention. The future research needs for ameliorating heat stress in livestock are to identify strategies for developing and monitoring appropriate measures of heat stress; assess genetic components, including genomics and proteomics of heat stress in livestock; and develop alternative management practices to reduce heat stress and improve animal well-being and performance.
Climate change has a profound impact on the availability and the safety of the food we consume and is expected to result in a significant increase in risk to public health through its effects on bacteria, viruses, parasites, and chemicals & toxins linked to foodborne diseases. Antimicrobial resistance and zoonotic diseases, both directly linked to food safety, are also expected to be affected by climate change. Various changes are driven by climate change influence behaviors that impact food safety, including human, animal and vector behaviors, and changing pathogen, organism, and pest survival, growth, and transmission behaviors. Such incidents are more likely to occur in countries where food monitoring and surveillance systems are less robust, therefore unable to detect environmental and chemical contamination, further increasing the risk to public health through the acute and chronic exposure to contaminants.
(Dr.J Abraham is the Founder Director, Centre of Excellence in Meat Science and Technology, Kerala Agricultural University, Thrissur, Kerala. Phone: 9447070919 E-mail: [email protected] )