REVIEW OF RELATED LITERATURE

2.1 INTRODUCTION

‘Climate Change’, the most uttered environmental term of present time has been used to refer to the change in modern climate brought predominantly by human being. It is perhaps one of the most serious environmental issues that today’s world population facing though the issue is not new. Ever since it emerged in the early nineteenth century, upto late twentieth century the issue was a topic discussed exclusively within the scientific society. In the mid to-late 1980s it first emerged on the public agenda Since then, in one hand, it has been manifested by the believers that consequence of human activities on world climate has reached to an alarming state and posing critical threats to physical, socio-economic structures. On the other hand, the sceptics have presented fairly enough evidence to disqualify the anthropogenic trait of Climate Change. Again, the Climate Change advocates among them have debated over the appropriate methods of addressing the eminent issue. Thus with increasing public involvement in the Climate Change discourse and ensuing awareness regarding the potential risks and uncertainties attached to the issue, it has been debated and problematized from diverse standpoints. While there has constant debate over the degree and agent of the change, methods to address the emerging risks but no doubt and debate over the fact that climate has been changing from the very beginning of the Earth’s history . How has this ever changing climate encountered this anthropogenic attribute over the time? In quest of the answer, the second part of this paper presents a brief definition of Climate Change and the way of manifestation of the issue in the environmental discourse over time. History of Climate Change discourse displays shift in angles from which the issue has been characterized and addressed time to time . Hence the third part examines the key perspectives of Climate Change and the assumptions that lie behind them as they relate to the larger debate surrounding the issue. This part in other words, attemts to analyze the philosophical background of the Climate Change science. The final part presents some hints perceived based on the analysis of problems in a new paradigm.

2.2 THERMOREGULATORY MECHANISM OF POULTRY BIRDS

The internal body temperature of domesticated gallinaceous birds (chickens) at 106°F to 108°F is measurably higher than that of mammalian livestock and humans (97°F to 102°F). The upper temperature

limit beyond which living cells and tissues progressively fail to operate is governed by the temperature at which enzymic proteins are destroyed by loss of shape and chemical activity. This starts to occur in the region of 46°C and thus poultry have considerably less leeway than other animals when suffering from heat stress and quickly succumb to higher temperature. In comparison, actual body temperature of poultry may fall as much as 20°C below the normal range with birds still making full recovery if carefully re-warmed. Poultry are not well adapted and disposed to high ambient air temperatures as they lack sweat glands in their skin and are therefore unable to gain much from natural evaporative cooling, although there is some direct diffusion of water through the skin tissue. Only the head appendages (e.g. comb) are very rich in blood vessels and able to act as sites for direct loss of heat, so poultry appears to have few limited options for heat loss in warm conditions. Domestic poultry is clearly less tolerant of heat than cold and much more likely to die from heat stress (hyperthermia) than succumb to stress associated with low temperature (hypothermia)

2.3 EFFECT OF CLIMATE CHANGE ON POULTRY PRODUCTION SYSTEM

As previously seen, exposure of birds to high environmental temperature generates behavioral, physiological and immunological responses, which impose detrimental consequences to their performance and productivity. Hot climate can have a severe impact on poultry performance. It inflicts heavy economic losses on poultry production as a result of stunted growth (Sahin et al., 2001), decrease in hen-day production (Njoku, 1989; Khan et al., 2003; Ayo et al., 2011), increased cost of production, high rate of mortality due to depressed immunity, and reproductive failure (Morsy, 1998; Obidi et al., 2008; Ayo et al., 2011).

2.4 GROWTH AND PRODUCTION EFFICIENCY

Heat stress depresses growth rate and production as a result of a down-turn in voluntary feed intake in birds (Sahin et al., 2001). It is apparent that the inhibition of growth and production in heat-stressed broiler birds is mediated via the stress hormones, especially the corticosteroids. Sahin et al. (2001) also showed that body weight in heat-stressed broilers was significantly lower than in birds administered with antioxidant vitamins A and E. Plasma triiodothyronine and thyroxine, which are important growth promoters in animals, were adversely affected in heat-stressed broiler chickens. Heat stress results in decreased feed consumption and increased water consumption. As temperature rises, the bird has to maintain the balance between heat production and heat loss and so will reduce its feed consumption to reduce heat from metabolism. Research demonstrated that feed consumption is reduced by 5% for every 1ºC rise in temperature between 32-38ºC. In a recent study (Sohail

et al., 2012) broilers subjected to chronic heat stress had significantly reduced feed intake (16.4%), lower body weight (32.6%) and higher feed conversion ratio (+25.6%) at 42 days of age. Many additional studies have shown impaired growth performance in broilers subjected to heat stress (Niu et al., 2009; Attia et al., 2011; Imik et al., 2012). However, in addition to decreased feed intake, it has been shown that heat stress leads to reduced dietary digestibility, and decreased plasma protein and calcium levels (Bonnet et al., 1997; Zhou et al., 1998).

2.5 EGG QUALITY

Heat stress limits the productivity of laying hens, as reflected by egg production and egg quality, as the bird diverts feed metabolic energy to maintain its body temperature constant, resulting in lower egg production, and particularly in lower egg quality (Esmay 1982; Teeter and Belay, 1993; Hsu et al., 1998; Tinoco, 2001). Under high environmental temperatures, layer respiratory rate increases from eases from approximately 29 cycles per minute (mild environmental temperatures) to more than 100 cycles per minute (environmental temperatures above the thermoneutral zone). The resulting hyperventilation decreases CO2 blood levels, which may decrease eggshell thickness in approximately 12% (Campos, 2000). CO2 is responsible for eggshell quality improvement, as it may promote acidosis, which is subsequently compensated by kidney uptake of bicarbonate. Therefore, heat stress causes losses in egg weight, egg shell percentage, egg shell weight, and egg specific gravity (Macari et al., 1994; Naas, 1992). Hsu et al. (1998) found that temperature increase significantly decreases feed intake, egg production, mean egg weight, and live weight, and also influence some egg quality traits, such as eggshell thickness and egg specific gravity. Muiruri and Harison (1991) studied the performance of layers maintained under thermoneutral (25°C) or hot (35°C) temperatures, and concluded that environmental temperature did not influence egg weight or feed conversion ratio, but egg production and feed intake significantly decreased. As to environmental ammonia concentration, Naas et al. (2007) and Wathes et al. (2002) found that ammonia concentrations higher than 20 ppm may cause respiratory disease and affect egg production. Studying the effects of light intensity on egg quality, Renema et al. (2001) observed a 12% incidence of eggs below 55g when light intensity was 500 lux, whereas no differences in egg weight were detected when light intensity was below 50 lux. Due to the importance of the environment on layer productivity, this study evaluated the correlations between egg quality parameters and environmental variables recorded at the time of lay of two layer genetic strains housed in battery cages in a commercial layer house

2.6 MEAT QUALITY

Climate change could affect meat quality in two ways. First, there are direct effects on organ and muscle metabolism during heat exposure which can persist after slaughter. For example heat stress can increase the risks of pale-soft-exudative meat in turkeys, heat shortening in broilers and dehydration in most species. Second, changes in poultry management practices in response to hazards that stem from climate change could indirectly lead to changes in meat quality. Also, pre-conditioning broilers to heat stress to encourage better survival during transport could lead to more variable breast meat pH. The impacts that short term climate change could have will vary between regions (Gregory, 2010). It has been reported that chronic heat exposure negatively affects fat deposition and meat quality in broilers, in a breed-dependent manner (Lu et al., 2007). In fact, recent studies demonstrated that heat stress is associated with depression of meat chemical composition and quality in broilers (Dai et al., 2012; Imik et al., 2012). Another recent study (Zhang et al., 2012) demonstrated that chronic heat stress decreased the proportion of breast muscle, while increasing the proportion of thigh muscle in broilers. Moreover, the study also showed that protein content was lower and fat deposition higher in birds subjected to hot climate

2.6 REPRODUCTIVE PERFORMANCE

Heat stress caused decreased production performance, as well as reduced eggshell thickness, and increased egg breakage (Lin et al., 2004). Additionally, heat stress has been shown to cause a significant reduction of egg weight (3.24%), egg shell thickness (1.2%), eggshell weight (9.93%), and eggshell percent (0.66%) (Ebeid et al., 2012). Heat stress affects all phases of semen production in breeder cocks (Banks et al., 2005). Although limited high temperature stimulates testicular growth in the early phase and promotes increased semen volume and concentration, a subsequent rise suppresses reproductive capacity as a result of a decrease in seminiferous epithelial cell differentiation, which is manifested in decreased semen quality and quantity with time (Obidi et al., 2008; McDaniel et al., 1996). McDaniel et al. (1996) showed that the broiler male broiler breeder was exposed to a temperature of 32°C, male fertility declined to 42% and in vivo sperm-egg penetration declined to 52%, compared to values obtained from males that were maintained at 21◦C, it may be concluded that heat stress has deleterious multiple effects on testicular function through inhibition of intracellular ion exchange. Report of McDaniel et al. (1996) showed that semen characteristics such as consistency, spermatozoa concentration, and seminal volume were depressed by environmental temperatures outside the zone of thermal comfort. In the study in which breeder hens were inseminated in the morning hours had a significantly higher fertility and hatchability than those obtained in inseminated hens during the afternoon hours (Obidi et al., 2008)

2.7 EMBRYONIC DEVELOPMENT

The incidence of adverse effects of heat stress on embryonic growth has been reported by various workers. Yalcin and Siegel (2003 and 2005) showed that over-heating fertile eggs during incubation resulted in differential tissue growth at different stages of incubation. The finding further showed asymmetries in skeletal development during the early and late stages of embryo development. Heat-stressed embryos, showed shorter face length and low lung weight, resulting in weaker chicks with high incidence of culled-out birds due to unsteady gait. A greater number of culled chicks as a result of unthrifty behavior. All the anomalies were due to heat stress suffered by embryo during the incubation process, induced by poorly controlled machine and environmental temperature due to frequent incubator electrical power failure. Findings of Deeming and Ferguson (1991) and Lourens et al. (2001 and 2007), showed that retarded embryonic and post-hatch chick developments are due to consistent heat stress.

2.8 IMMUNITY

In poultry, several studies have investigated the effects of hot climate on the immune response in recent years. In general, all studies show an immunosuppressant effect of heat stress on broilers and laying hens. For instance, lower relative weights of thymus and spleen has been found in laying hens subjected to heat stress (Ghazi et al., 2012) reduced lymphoid organ weights have also been reported in broilers under heat stress conditions (Bartlett and Smith, 2003; Niu et al., 2009). Additionally, Felver-Gant et al. (2012) observed reduced liver weights in laying hens subjected to chronic heat stress conditions. Bartlett and Smith (2003) observed that broilers subjected to heat stress had lower levels of total circulating antibodies, as well as lower specific IgM and IgG levels.

2.9 CLIMATE CHANGE AND THE FUTURE AVAILABILITY OF THE SCAVENGEABLE FEED RESOURCE BASE (SFRB) FOR FAMILY POULTRY

Climate change has become a global issue. The current world average temperature is 15° C and this is increasing at an alarming rate. The destruction of forest areas, carbon emissions, methane output, industrial activities, an increase in the concentration of harmful green house gases, increase in sea level etc. are continuously contributing to global warming. There is a possibility of increasing world temperature by 3-5° C within the near future resulting in a further increase of sea level by 1.5 meter. The impact of climate change is detrimental for agricultural production. Although world leaders are thinking to find ways to reduce the negative impact of climate change, little progress has been made so far. The most vulnerable groups to such climate change are the developing countries and its consequences are many and quite visible. The agricultural production including poultry can be threatened by its detrimental effects. Taking the example of Bangladesh, millions of people from southern coastal areas whose main occupation is agriculture have been uprooted due to a loss of homestead areas by sea/river erosion and every year cyclone, tidal surge and flood damage are quite common resulting in innumerable sufferings of the people. In many African countries, deforestation, soil erosion and decreasing fertility and even desertification are major challenges to agricultural production. Moreover, the competition between human and animal nutrition exacerbates the feed shortage. As pointed out by Nellemann et al. (2009) there is a growth in food demand and need as a result of the combined effects of world population growth, rising incomes and dietary changes towards higher meat intake that is particularly demanding in terms of energy, cereal and water with nearly half of the world’s cereals being used for animal feed. Indeed, with an increasing population in developing countries, the pressure on land for building houses, roads and high-ways, schools, colleges and universities is increasing. The urban and industrial areas are also increasing with a consequent decease in homestead areas. People are moving towards urban and industrial areas for employment. According to Steinfeld (1998) “the rapidly increasing demand for livestock products pushes against a traditional resource base for livestock production that cannot expand at the same pace”. De Haan (1998) suggests that most likely, the major growth would therefore have to come from the industrial system, and mostly among others, the intensive poultry production. So, there is a clear relationship between impact of climate change, population growth and future availability of the scavengeable fed resource base (SFRB). Feed resources available for scavenging poultry in South-east Asia were identified and classified by several scientists (Roberts and Senaratne, 1992; Gunaratne et al., 1993; Gunaratne et al., 1994; Roberts, 1999). Some of the African studies include those of Olukosi and Sonaiya (2003) and Sonaiya et al. (2002). According to Sonaiya and Swan (2004) the Scavengeable Feed Resource Base (SFRB) is the total amount of food products available to all scavenging animals in a given area. In fact, the homestead area, the types of food crops grown and cultivated and processing methods of different crops as well as climatic conditions that determine the rate of decomposition of the food products are the factors affecting the total available SFRB for scavenging poultry. SFRB is also influenced by the season of the year due to periods of fallow or flooding, monsoon, cultivation, harvesting and processing. Depending on country and seasons, SFRB includes termites, snails, worms, insects, grains, harvesting by-products, seeds, grass, fodder and tree leaves, aquatic weeds and plants and non- traditional feed materials. The SFRB can only be harvested by scavenging animals, of which poultry are the most versatile, although this varies with species. Several types of poultry scavenging together can make most effective use of this resource. Keeping poultry under the free-range and backyard systems and obtaining production depends to a large degree on the quality of feed available from scavenging. Having said the above, the impact of climate change in terms of global warming, monsoon, disasters etc. on the availability of SFRB for family poultry production need to be discussed. The following points may help with analyzing the situation and assessing the availability of SFRB in developing countries: (a) How and to what extent may climate change affect FP production and the availability of the SFRB and which may be influencing factors like seasons and other circumstances ? (b) What will be the future availability of SFRB under changing circumstances such as urbanization, industrialization etc? All these factors can affect the future availability of SFRB and consequently FP production and it will therefore be worthwhile to analyze these developments.

2.9 GREENHOUSE EMISSIONS FROM POULTRY PRODUCTION

Greenhouse gas emissions are generated from poultry housing areas, manure storage, manure treatment and manure land application from both meat and egg poultry production operations. The Intergovernmental Panel on Climate Change (IPPC) GHG emissions methodologies include emissions from both meat and egg production systems. Categories include confined broiler chickens, ducks and turkeys and free range chicken and turkey systems for meat production. The IPPC inventories include dry and wet manure management confinement layer systems as well as free range chicken systems for egg production. The IPPC also considers geese and ostrich production in their calculations we well (Dong et al., 2006) Both poultry meat production and egg production have been increasing, in a large part due to an increase in per capita consumption of both poultry meet and eggs in Asia As noted, the world consumption of both poultry meat and eggs has shown a continual increase over the past decade. The majority of GHG emissions data available to date is for broiler and layer operations, although some data can also be found for turkey, duck and goose production systems as well. Many studies report emissions on an average bird mass. However, because meat poultry are gaining weight throughout the grow-out cycle it is more appropriate to use emission factors for a per bird produced basis than to use average bird weight to estimate emissions. Emissions of CO2 , N2O and CH4 can be released from animal housing areas. While bird respiration and manure produces CO2 emissions, the current IPCC Guidelines for National Greenhouse Gas Inventories do not consider CO2 generated by livestock or poultry to be a source of emissions that should be included in GHG inventories. These CO2 emissions are not considered in GHG emission inventories because they are assumed to be zero on a net annual basis. It is assumed that the CO2 generated by livestock and poultry respiration and manure storage and handling will be photosynthesized by crops and plants used as animal feed in the annual production cycle and as such does not contribute to increasing GHG concentrations in the atmosphere over the long term. As such, GHG emissions inventories based on IPCC methodology do not include CO2 emissions from livestock or poultry respiration or manure. Methane can also be produced directly by poultry through enteric fermentation. Methane emissions from enteric fermentation from poultry are many times considered negligible and not included in poultry GHG emission inventories. The IPPC GHG emission calculation methodologies for example, do not have an enteric CH4 emission factor for poultry. While significantly less enteric CH4 are generated from poultry compared to ruminant livestock, poultry do produce some enteric CH4 emissions. Wang and Haung reported enteric CH4 and N2O emissions from commercial broiler chickens, Taiwan country chickens and White Roman Geese based on respiration chamber studies (Wang and Haung, 2005).