Epidemiological Studies on Environmental Pollution in Poultry Farms

Introduction

Poultry provide globally important sources of animal protein and are amongst the most intensively reared of all livestock species. Diseases of poultry are therefore of major concern, both locally and on an international scale. Poultry production have been brought to the edge, because of the large numbers of infectious diseases outbreaks; that strikes the poultry farms from time to time in the absence of good hygiene. It is also important to consider the concept of, and the need for, biosecurity or the range of management procedures designed to protect livestock from infection.

The low productivity in traditional systems is mainly due to high mortality, which is caused by mismanagement, diseases, lack of nutritional feeding and predators. In traditional systems the mortality has been estimated to be in the range of 80 - 90% within the first year after hatching, (Permin and Bisgaard, 1999). Diagnosis, treatment and/or prevention of diseases are of major importance to any attempts at increasing productivity. Backyard poultry production systems (BPS) are an important and widespread form of poultry production. There is a common perception that biosecurity standards in BPS are generally poor and BPS are usually associated with poultry diseases and zoonoses, (Hamilton-West, et al, 2011)

The structure of the poultry meat and egg production industries provides both challenges and opportunities in the area of poultry health; one of these challenges is the existence of very high-density populations of commercial poultry. Such circumstances provide an ideal medium for multiplication and spread of all kinds of micro-organisms including pathogens, such as Salmonella spp that can strike all ages specially chicks and still considered one of the most important world wild food poisoning diseases, ( Vugia, et al, 2006).

The importance of Salmonella bacterium has increased dramatically in recent years since it assumed a political role to complement its pathogenic one. Only a few serotypes out of some 3000 caused disease in poultry but most of Salmonella serotypes, given the right set of circumstances, can cause food poisoning such as Salmonella enterica serovar Enteritidis & Typhimurium which are the world leading cause of Salmonellosis and is often implicated in over 60.0% of human Salmonellosis, (Patrick, et al, 2004). The current world wide epidemic of Salmonella enteritidis started in the middle of (1980s); (Ward, et al , 2000), the reservoir of Salmonella enteritidis is mainly poultry often carrying asymptomatic infection, which pass the human pathogen along the food production chain. Especially undercooked or raw eggs and frozen poultry meat represent a high risk for humans. Salmonella enteric serovar typhimurium and enteritidis are known as the persistent serotypes among single age flocks, with a correlation between qualitative environmental samples and semi quantitative fecal samples; and there were significant temperature and seasonal effects upon contamination that was increased significantly over time (Wales, et al., 2007).

The success in modern production is very much dependent on being able to produce uniform, quality stock of a high health status. This, in turn, relies on quality of management in order to reduce illness, which was why epidemiological measures have been implemented to reduce the source(s) of infection. Because poultry and poultry products often serve as the vehicles for salmonellosis, (Bean and Griffin, 1990; Persson and Jendteg, 1992; Henson, 1997; Lynch, et al, 2006), the United States Department of Agriculture (USDA) and Food Safety Inspection Services (FSIS) implemented an “in plant” Hazard Analysis Critical Control Point (HACCP) program to reduce the prevalence of the food borne pathogen contamination in meat and egg and eradicating Salmonella in live birds and at the processing plant, (Hargis, et al, 2001).

As in other husbandry fields, the aim in chicken production is to obtain the yield in a desirable level at the lowest cost. As the chickens have spent their life in poultry houses, in order for the chicken to be able to perform their yield capacities entirely, they should be kept in a good environmental conditions with a good care as well as genetic features. An adequate environment within poultry houses is a very important requirement for success in the poultry industry. In poultry houses environmental conditions mean physical (heat, humidity and air movement) and chemical factors (ammonia and carbon dioxide in the compound of the air).

The survival of Salmonella spp in poultry house environment is dependent on both physical and chemical factors such as temperature, water activity (Aw) or equilibrium RH (ERH), moisture content, and pH. Whenever extrinsic factors fall outside; the optimum range for microbial growth and survival is achieved, these factors can cause cellular damage depending on the severity of the stress factors, growth can be inhibited or cell death can occur, (Farkas, 2001).

The survival of avian pathogens outside the animal body varies considerably depending on the species of the agent, weather and if it is protected with organic matter or not. The objective of disinfection is to reduce microbial population; (Eckman, 1994), as disinfectants act on microorganisms at several target sites resulting in membrane disruption, metabolic inhibition, and lysis of the cell; (Denyer and Stewart, 1998; Maillard, 2002). Removal of old litter followed by cleaning and disinfection of facilities helps to reduce the number of pathogens and break disease cycles or at the minimum, keep pathogen numbers from reaching a level that can cause disease outbreaks. In addition, as live production becomes the target area of programs for the reduction of human pathogens such as Salmonellae on poultry carcasses, it will become necessary to document that sanitation procedures are effective. Unfortunately, poor sanitation procedures and/or increased soil moisture levels have been linked to increased or sustained bacteria levels, (Rudolfs, et al., 1950; Pepper, et al., 1993).

Several studies were carried out on disinfectants and many of these disinfectants are not considered to be environmentally safe e.g. gluteraldhyde, formaldehyde to show their effectiveness against Salmonella; (Ramesh, et al., 2002; Gradel, et al., 2003-2004). Further, poultry houses have inaccessible equipment and considerable amounts of organic matter and high contents of protective compounds (fats, carbohydrates, and proteins) from which Salmonella are difficult to remove; (Gradel, et al., 2004). On the other hand, water hardness, low temperature, and biofilm development also decrease efficacy of disinfectants; (Tylor and Holah, 1996; Gradel, et al., 2004; Lapidot, et al., 2006).

This study was conducted for:

1. Epidemiological survey for the most frequent environmental pathogenic micro-organisms, which may strike in the poultry farms.
2. The influence of ambient environmental conditions (Temperature, Relative Humidity, air gases including ammonia and carbon dioxide) on broiler growth and performance.
3. The survival of Salmonella typhimurium in poultry litter under influence of different ambient environmental conditions.
4. Evaluation of the efficacy of some safe commercial chemical disinfectants in treating contaminated poultry litter i.e. safe to both applicant and birds.

Review of Literature

I. Epidemiological survey for the most frequent environmental pathogenic micro-organisms in the poultry farms

A. Epidemiological survey for the most frequent bacterial pathogens in the environment of broiler farms in Egypt

Advances in technology over the last century have greatly increased the scale of both crop and livestock agriculture. In the past 50 years, poultry production and consumption of broiler meat has increased by approximately 4% per year, (Ollinger, et al., 2005). Despite its economic benefit, the high stocking density of birds in a house has spawned numerous health issues for both birds and humans; (Boyd, 2001). In part, these issues arise from the volume of litter produced in a poultry house. Plant-based bedding material along with chicken excrement, feathers, and spilled feed are the principal components of litter.

The introduction and survival of zoonotic bacterial pathogens in poultry farming have been linked to bacterial association with free-living protozoa, (Barẻ, et al., 2011).

E. coli was the most predominated organism in water, food, air, dust and litter of broiler houses. These strains caused coli septicaemia outbreak in poultry, (Harry and Hemsly, 1965). The microbial contamination inside broiler houses reached the maximum rates at the 4th and 5th weeks of age. The highest number of air microbe carrying particles inside broiler houses was found in winter and the lowest in spring, E. coli, Proteus, Klebsielia, Pseudomonas, Citrobacter and Enterobacter were isolated from cloacal swabs, (Tork, 1986).

Staphylococcus aureus was also isolated from air of open poultry house in summer and winter with a percentage of 4 and 8% respectively. The respective values were 10 and 15% for E. coli; 9 and 10% for Pseudomonas sp and 18 and 17% for Proteus sp, the seasonal variation in rates of isolation from litter samples were 18 and 16% for E. coli; 6 and 7% for Staphylococcus aureus, 16 and 14% for Proteus species and 11 and 14% for Pseudomonas sp in summer and winter respectively, (Zahran, 1980).

Moghney (1998) isolated Escherichia coli, Staph. aureus, Strept. avium, Pseudomonas spp., Proteus vulgaris from examined litter, water and air samples collected from broilers farms in Behera Province, Egypt.

Abd El-Alla (2001) examined air samples from four commercial broiler houses and found that the isolated bacteria were Staph. aureus, Strept. Faecalis, Strept. intermediate, Strept. faccium, Escherichia coli, Klebsiella pneumonia, Klebsielia oxytoca, Proteus mirabilis, Eneterobacter cloacae and Citrobacter freundi with a percentage of 14.5, 56.2, 37.5, 14.5, 45.8, 18.7, 18.7, 12.5, 25 and 22.9% respectively.

Maji, et al., (2002) examined 62 small to large private poultry farms and 3 organized poultry farms from September 1996 to August 1997 in west Bengal. Mortality percentage was 37.66%. The highest mortality in birds was recorded in birds of one day old until the second week age and this may be due to unabsorbed yolk sac followed by E. coli infections, broiler Pneumonia and Avitaminosis.

- examined poultry farms with spontaneous occurrence of coli septicemia and infectious bursal disease. Samples were collected from 112 suspected poultry farms (96 from layers and 16 from broilers farms). Swabs were taken from heart blood, liver, lungs, air sac, trachea, spleen, kidney, peritoneum, bursa, ovary and oviduct. Fourteen E. coli isolates were isolated from 16 broiler farms. The incidence of coli- septicemia was higher in broilers (87.5%) compared with layers (76.04%). Occurrence of coli septicemia was higher in deep litter system (86.6%) than in cage system (61 .6%). The mortality rate was recorded between 9 and 15%.
- found that air analyses show airborne bacteria, dust and endotoxines in poultry and livestock houses. Average amount of microorganisms and Gram negative bacteria isolated from poultry houses (p‹0.01) and the concentration of dust was higher than that of cowsheds. The presence of a closed association was found between dust and airborne bacteria.
- determined the basic microclimatic factors that affect bacteria and mould in the air of fattening poultry houses, like air temperature, relative humidity, air velocity and levels of CO2, NH3, bacteria and mould in the air. The bacteria isolated from the air of poultry fattening houses were Serratia sp, Pseudomonas sp, Pantoea sp, Micrococcus sp, Escherichia coli and Klebsiella spp., the dominant fungi were Aspergillus flavus and Rhizopus sp, while the dominant yeast was Mucor sp. Microclimatic parameters were within the allowable limits except for the relative humidity and air velocity which were below the allowable limits.

Karwowska (2005) evaluated the microbiological contamination levels of indoor air in some farms, including barns. The level of micro-organisms emission from farm building to the atmosphere was also estimated. It was found that the number of microorganisms in the barn ranged between 1.7.103:8.8.104 for mesophilic bacteria, 3.5.101:8.3.102 for hemolytic bacteria, 1.5.103:4.6.104 for Staphylococci, 5.100:2.102 for coliform group bacteria and 1.7.102:2.4.104 for mould (Mainly Penicillium, Aspergillus, Alternaria, Cladosporium, mucor and Rhizopus) there were no significant differences of microbiological air contamination between buildings of old and modern types.

Lovanh, et al., (2007) stated that microbial populations within poultry litter have been largely ignored with the exception of potential human or livestock pathogens. They correlated poultry litter air and physical properties to shifts in microbial community structure as analyzed by principal component analysis (PCA) and measured by denaturing gradient gel electrophoresis (DGGE). Litter samples were taken in a 36-point grid pattern at 5 m across and 12 m down a 146 m x 12.8 m chicken house. At each sample point, physical parameters such as litter moisture, pH, air and litter temperature, and relative humidity were recorded, and samples were taken for molecular analysis. The DGGE analysis showed that the banding pattern of samples from the back and water/feeder areas of poultry house were distinct from those of samples from other areas. There were distinct clusters of banding patterns corresponding to the front, middle front, middle back, back, and waterer/feeder areas. The PCA analysis showed similar cluster patterns, but with more distinct separation of the front and midhouse samples. The PCA analysis also showed that moisture content and litter temperature (accounting for 51.5 and 31.5% of the separation of samples, respectively) play a major role in spatial diversity of microbial community in the poultry house. They concluded the presence of differences in the types of microorganisms over the length of the house, which correspond to differences in the physical properties of the litter.

Esteban, et al., (2008) in a survey of the occurrence of Campylobacter, Salmonella, Listeria and Shiga toxin-producing E. coli was performed on 60 flocks of free-range chicken from 34 farms in the Basque Country (Northern Spain). Campylobacter was the most prevalent of the four pathogens, isolated from 70.6% of the farms, followed by L. monocytogenes (26.5%), and Salmonella (2.9%). No E. coli O157 or other STEC were isolated. In a total of 48 flocks from 26 farms were found positive for at least one pathogen: 31 of them for a single pathogen (64.6%), and 17 for more than one species (35.4%). C. coli was more prevalent than C. jejuni (15 vs. 13 farms), and both species of Campylobacter were found in 3 farms . L. monocytogenes isolates were identified as serotype 4b complex, and the only Salmonella isolated was serovar Enteritidis. flaA PCR-RFLP performed on 91 Campylobacter isolates (36 C. jejuni and 55 C. coli) yielded 26 patterns, with higher diversity among the C. jejuni isolates. More than one pattern was found in 11 farms, and in 8 of them several patterns were found within the same flock.

Chinivasagam, et al., (2010) examined litter samples collected at the end of the production cycle from a single shed from 28 farms distributed across the three Eastern seaboard States of Australia. The geometric mean for Salmonella was 44 MPN/g for the 20 positive samples. Five samples were between 100 and 1000 MPN/g and one at 105 MPN/g, indicating a range of factors are contributing to these varying loads of this organism in litter. The geometric mean for Campylobacter was 30 MPN/g for the 10 positive samples, with 7 of these samples being <100 MPN/g. The low prevalence and incidence of Campylobacter were possibly due to the rapid die-off of this organism. E. coli values were markedly higher than the two key pathogens geometric mean 20x105cfu/g with overall values being more or less within the same range across all samples, suggesting a uniform contribution pattern of these organisms in litter. Listeria monocytogenes was absent in all samples and this organism appears not to be an issue in litter. The dominant (70% of the isolates) Salmonella serovar was S. Sofia and was isolated across all regions. Other major serovars were S. Virchow and S. Chester (at 10%) and S. Bovismorbificans and S. Infantis (at 8%) with these serovars demonstrating a spatial distribution across the major regions tested.

Choo, et al., (2011) found that insects, in particular house flies and cockroaches, have been shown to be associated with the spread of pathogens in livestock farms and in human disease outbreaks: among these pathogens are salmonellae and campylobacters. A total of 60 flies were caught in three locations: an animal teaching facility and a cafeteria in a university campus, and a poultry farm. Five percent (5%) and 13.3% of flies sampled were found to carry Campylobacter and Salmonella, respectively.

Dumas, et al., (2011) studied differences in the distribution of bacterial phylotypes between Wet and Dry litter samples and between houses. Wet litter contained greater diversity with 90% of total bacterial abundance occurring within the top 214 OTU clusters. In contrast, only 50 clusters accounted for 90% of Dry litter bacterial abundance. The sixth largest OTU cluster across all samples classified as an Arcobacter sp., an emerging human pathogen, occurring in only the Wet litter samples of a house with a modern evaporative cooling system. Ironically, the primary pathogenic clostridial and staphylococcal species associated with GD were not found in any house; however, there were thirteen 16S rRNA gene phylotypes of mostly gram-positive phyla that were unique to GD-affected houses and primarily occurred in Wet litter samples. Overall, the poultry house environment appeared to substantially impact the composition of litter bacterial communities and may play a key role in the emergence of food-borne pathogens.

Hong, et al., (2012) revealed that the airborne microbial community skewed towards a higher abundance of Firmicutes (>59.2%) and Bacteroidetes (4.2-31.4%) within the confinement buildings, while the office environment was predominated by Proteobacteria (55.2%). Furthermore, bioaerosols in the confinement buildings were sporadically associated with genera of potential pathogens, and these genera were more frequently observed in the bioaerosols of pig and layer hen confinement than the turkey confinement buildings and office environment. High abundances of tetracycline resistance genes 9.55×102 to 1.69×106 copies were also detected in the bioaerosols sampled from confinement buildings. Bacterial lineages present in the poultry bioaerosols clustered suggesting that different livestock as well as production phase were associated with a distinct airborne microbial community.

B. Epidemiological survey for Salmonella spp in broiler farms in Alabama State, USA

Poultry are commonly infected with a wide variety of micro-organisms with special attendance to the world wide problem Salmonella serovars, which are able to strike at any age and any time in poultry farms. Infections with Salmonella are generally subclinical, and one serovar may be a predominant isolate in the country for several years before it is replaced by another serovar,(Wray, et al., 1996). The two serovars that have been of most concern in recent years are Salmonella enteritidis, and Salmonella typhymurium . These invasive strains of Salmonella may cause disease in young chicks. However, their ability to cause severe disease in humans has led to government backed measures to control these infections in chickens. Salmonella is a frequent cause of food-borne illness and contaminated poultry products are the major sources of infection for humans.

Salmonella enteritidis may produce clinical disease in chicks up to six weeks of age, and occasionally in adult laying hens. Affected birds are depressed, reluctant to move and commonly have diarrhea,(Wray, et al. , 1996). Mortality may be high in chicks under one week of age. Older chicks may show uneven growth and stunting and birds may be rejected at slaughter with lesions of pericarditis and septicemia,(O’Brein, 1988) and (Lister, 1988).

Infection of adult chicken with Salmonella enteritidis is largely asymptomatic,(Hopper and Mawer, 1988) and (Lister, 1988), however the organism was recovered from the ovary, oviduct, and caeca of infected birds and from the soft shell, and content of eggs, and older birds become chronic carriers of Salmonella enteritidis .

The main route for transmission of Salmonella enteritidis is vertically by the eggs. In integrated poultry organization, infection of breeders flocks with Salmonella enteritidis lead to rapid dissemination of the organism to progeny broiler and commercial egg layer. Salmonella enteritidis is also spread horizontally between birds by the fecal oral route. The bacterium survives for long period in the environment, and has been isolated from the litter, and dust in poultry houses(Hopper & Mawer, 1988).

To reduce Salmonella contamination in or on the final food products, procedures may need to reduce its prevalence in bird; that is brought to the processing plant. Also producers have to identify the source of Salmonella within the setting, in order to have effective control points ( Sanchez, et al., 2002).

Gustafson and Kobland (1984) determined the effect of three variables on the incidence of Salmonella in broilers challenged at four days of age. These variables were presence/absence of food additive, avopracin, and the use of new/used litter and the initiating dose of Salmonella. Cloacal swabs were taken from approximately 600 birds at weekly intervals for 45 days; the chicks were raised on used litter showing an appreciable reduction in susceptibility of Salmonella when compared to those raised on fresh litter. Avopracin in the diet at 10ppm had no enhancing effect on Salmonella shedding, and any time during the 45 days sampling period.

Lahellec, et al., (1986) conducted an epidemiological survey of 5329 samples from ten poultry operations to determine the relationship between total poultry farm environment and incidences of Salmonella contamination of broiler flocks. Samples were analyzed from walls, drinkers, feeders, litter, insects, water, chicks, broilers, and feed to determine the effect of common sanitary practices on Salmonella contamination of flocks. Results indicated that although similar hygienic practices had been taken on the 10 poultry farms examined, great variation exists in Salmonella contamination among the farms.

Ooesterom (1991) concluded that human salmonellosis is a serious problem all over the world. The major source for human salmonellosis is caused by farm animals, which may frequently be intestinal carriers of the organism. Particularly pigs and poultry are incriminated in this respect, and, to a lesser degree, cattle and sheep. Because generally no symptoms of disease can be observed, these animals usually pass veterinary slaughterhouse inspection without restrictions. During slaughter however, intestinal material, often containing Salmonella bacteria, pollutes the surface of carcasses, which in later stages may lead to extensive Salmonella contamination of meat and meat products.

Mutalib, et al., (1992) collected Seven hundred fifty-one environmental samples from 76 chicken layer houses in a voluntary Salmonella enteritidis (SE) survey study carried out in New York state between January 15 and April 8, 1991. SE was recovered from both houses on 1 farm. Sampling of manure pits and mice in hen houses was useful for SE screening. Phage types of SE from the environment, birds, and mice were identical. The rapid whole-blood test was unreliable, and culture of cloacal swabs was inadequate for detection of SE carriers. Culture of organs from chickens did not correlate well with results of environmental samples.

Van de Giessen, et al., (1994) presented a model of the cumulative infection curve of S. enteritidis in laying flocks. Based on this model and practical results the contribution of different routes to the infection can be estimated providing a basis for an effective intervention strategy. They suggested that the laying flocks become infected mainly from the farm environment including not properly cleaned and disinfected poultry houses and infected vermin present on the farm. As a consequence, intervention in The Netherlands should be directed to trace S. enteritidis -contaminated laying farms and eradicate the contamination.

Caldwell, et al., (1995) evaluated the consistency and persistence of isolation of specific serotypes of Salmonella on a 31-farm broiler complex following four complete sampling periods. A total of 25 different serotypes were isolated, with multiple serotypes and were frequently isolated simultaneously from individual farms. These results indicate little predictability or consistency of Salmonella serotype isolation on individual farms over time.

Caldwell, et al., (1998) tested the hypothesis that the frequency of Salmonella isolation from protective foot covers worn in individual broiler production houses would compare favorably to isolation rates obtained from conventional drag-swab methods. Salmonella was detected with equal frequency from protective foot covers and drag-swab assemblies on nine individual broiler farms over three separate sampling periods. Salmonella was detected in 13 of a total 27 individual samplings by culturing the protective foot covers, whereas positive detections occurred in 16 of a total 27 samplings when using the drag-swab method. To highlighting the development of a potential new Salmonella monitoring technique, this study reinforces our current understanding regarding the importance of stringent biosecurity practices on poultry farms.

Limawongpranee, et al., (1999) examined cecal and environmental samples for the presence of Salmonella on a farm where a high prevalence of Salmonella blockley in chickens was observed. Of 895 cecal and 525 environmental samples examined, 242 (27.0%) and 202 (38.5%) samples, respectively, yielded S. blockley. Salmonella blockley was isolated from environmental samples such as floor litter, walls, drinking water, waste water, dust, and soil collected when barns were occupied and was positive in drinking water, waste water, and soil when samples were collected from empty barns with occupied neighboring barns, but it was negative in all environmental samples with the exception of soil when the environmental samples were collected from empty barns with empty neighboring barns.

Lillehoj, et al., (2000) stated that chickens are housed routinely in crowded environments under adverse conditions, and genetic strains have been selected for rapid growth, high protein-to-fat content and superior egg-laying characteristics. A major negative consequence of these practices has been an increase in the incidence of diseases. A variety of methods have been used to combat avian diseases in the commercial setting, including improved farm management practices, the use of antibiotic drugs, the selection of disease-resistant strains of chickens, and the manipulation of the chicken's immune system.

Murase, et al., (2001) examined two chicken houses and an attached egg-processing facility in a laying farm between 1994 and 1998 to investigate Salmonella contamination. Each of the houses was environmentally controlled and fitted with egg belts that transported eggs from the houses to the egg-processing facility. Four hundred twenty-eight Salmonella isolates were obtained from 904 environmental samples collected from the houses. Strains having an identical pulsed-field gel electrophoresis (PFGE) pattern were continually recovered from a house for more than 1 year. Several strains of Salmonella Cerro, Salmonella Mbandaka, and Salmonella Montevideo obtained from both the houses and from the egg-processing facility were indistinguishable by PFGE, respectively. They also suggested that Salmonella organisms originating from a single clone colonized the chicken houses and that the egg belts are likely to be one of the means by which Salmonella organisms are spread from one house to the others.

Roy, et al., (2002) isolated out of 4745 samples about 569 Salmonella, which were identified according to their source, serogrouping, serotyping, phagetyping, and tested for antibiotic sensitivity. Food product samples (rinse water of spent hens, and broilers and chicken ground meat); and poultry environmental samples; as well as internal organs samples (liver, and yolk sac content) were tested. About 92 Salmonella were serotyped and tested for drug sensitivity.

Northcutt, et al., (2003) determined the effects of bird age at slaughter, feed withdrawal, and transportation on levels of Salmonella on carcass before and after immersion chilling. One week before slaughter, broilers were gavaged with nalidixic acid- resistant Salmonella. The whole carcass was rinsed before and after immersion chilling with 20ppm sodium hypochlorite, and the rinse was analyzed for Salmonella. They concluded that contamination on the exterior surface of the bird entered to processing is critical to carcass bacterial counts. Moreover carcass bacterial count didn’t vary when microbial content of the broilers were comparable.

Traub-Dargatz, et al., (2006) determined if there is an impact of heat stress of broiler chickens on number, and survival of two types of Salmonella shed in the chicken’s faeces after an oral challenge. They found that heat stress didn’t result in higher levels or longer survival of Salmonella species shed in faeces. It may be possible that the duration, and intensity of heat stress was not sufficient; or that heat stress doesn’t alter the number or survivability of these particular strains of salmonella. Faeces stored at the room temperature after collection resulted in the numbers of both strains of salmonella increasing by one to three log in the first week, indicating that there could be an increase in environmental contaminant under certain conditions.

Higgins, et al., (2007) evaluated the ability of a commercial available lactic acid bacteria based probiotic culture to reduce Salmonella enetritidis in day of hatch broiler chicks. Chicks were challenged with Salmonella enetritidis and treated with LAB 1 hour post-challenge. Following treatment, cecal tonsils and ceca were aseptically collected for Salmonella enetritidis. They found that LAB significantly reduced the recovery of Salmonella enetritidis from the cecal tonsils at 24 hours, but not 6 or 12 hours post-treatment, although in cecal tonsils samples there was no difference in Salmonella enetritidis incidence at 12 hours. LAB treatment significantly reduced the recovery of Salmonella in day of hatch broilers.

Huezo, et al., (2007) investigated the effect of chilling method on concentration, and prevalence of Salmonella recovered from chicken carcasses, the results demonstrated that air and immersion chilled carcasses without chemical intervention are microbiologically comparable, and chilling method had no effect on prevalence of Salmonella recovered from carcasses.

Burkholder, et al., (2008) conducted an experiment to determine the influence of 24 hours feed withdrawal and 24 hours exposure to high temperature 30 degree C on intestinal characterization of broilers. Attachment of Salmonella enetritidis to ileal tissue was determined using an in vitro ileal loop assay. They found that acute stressors in poultry production systems can cause changes in the normal intestinal microbiota and epithelial structure, which may lead to increased attachment of Salmonella enetritidis.

Cho, et al., (2008) investigated the molecular relatedness among Salmonella enetritidis isolates from different sources. They concluded that differences in allele distribution, and genetic diversity of VNTR loci in Salmonella enetritidis isolates from different sources were found. Polymorphism in most of VNTR loci was more frequent among human Salmonella enetritidis isolates than isolates from chicken or eggs. Therefore, VNTR profiles of Salmonella enetritidis from a specific source should be further evaluated as potential markers in epidemiological investigation to trace Salmonella enetritidis to their probable source.

Dunkley, et al., (2008) investigated an outbreaks, and sporadic cases that have indicated that food vehicles such as poultry and poultry by-products including raw and uncooked eggs are among the most common sources of Salmonella infections. The dissemination and infection of the avian intestinal tract remain somewhat unclear, but in-vitro incubation of Salmonella with mammalian tissue culture cells has shown that invasion into epithelial cells is complex and involves several genetic loci and host factors. The study showed that the toxic effect of short chain fatty acids to some Enterobacteriaceae including Salmonella, have resulted in reduction in population. In addition, it has been established that native intestinal micro-organisms such as Lactobacilli provide protective mechanism against Salmonella in the ceca.

Miljković-Selimović, et al., (2008) stated that illness caused by Salmonella enteric serovar enetritidis occurred not only as sporadic cases but as outbreaks, to reveal the source and routes of spreading of infection it is necessary to identify epidemic strain by the use of some typing methods. They also concluded that the strain of Salmonella enteric serovar enetritidis isolated in outbreaks of enterocolitis as well as from sporadic cases of diarrhea in the same period of time at the same area, frequently exhibits the same plasmid profile characterized by a single plasmid of 38 MDa. Therefore plasmid profile analysis in most case is not valuble in identification of epidemic strain of Salmonella enteric serovar enetritidis.

Nisbet, et al., (2008) conducted two experiment to evaluate the effect of melatonin on Salmonella enterica serovar enteritidis infection in experimentally challenged laying hen subjected to forced molting, in the first experiment; they notice that concentration of Salmonella enterica serovar enteritidis in the cecal content, and the number of Salmonella enterica serovar enteritidis positive tissue from crop, liver, ceca, spleen, and ovary were higher in the molt compared with the control, in experiment II; cecal concentrations of Salmonella enterica serovar enteritidis were generlay higher in the molt compared with the control treatment and within molted birds, and from the experiment they noticed that dosage with high level of melatonin may exacerbate Salmonella enterica serovar enteritidis infection in layers subjected to forced molt.

O’Regan, et al., (2008) developed PCR assay for the detection of multiple Salmonella serotypes in chicken samples. The real time PCR showed 100% inclusivity and 100% exclusively on all the tested strains, beside they test the relative accuracy, relative sensitivity, and relative specificity and found to be 89, 94 and 87%, respectively. They concluded that; real time PCR methodology may contribute to meet the need for rapid detection and identification in food testing laboratories.

Smith, et al., (2008) investigated four outbreaks of Salmonellosis associated with raw, frozen, microwaveable, breaded, prebrowned, and stuffed chicken products. Most individuals affected through that the product was precooked due to its breaded and prebrowned nature, most use microwave oven and didn’t follow the instruction of package cooking, so inadequate labeling, customer response to labeling and microwave cooking were the key factors in the occurrence of the outbreaks.

Van Immerseel, et al., (2008) stated that the most important regulator of the invasive process is the hilA gene. They used transposon bank approach to identify DNA sequences affecting expression of hilA. Mutants with decreased hilA expression carried mutation in known virulence gene regulator (fliZ, hilD, sirA), genes encoding ion transport proteins (feoA, feoB, pstB, pstC), genes involves transcription/translation machinery (nusA, selA), and the hypothetical inner membrane protein STM2303, mutants having increased and decreased hilAexpression were more and less invasive in the human colon carcinoma cell line T84 compared to wild type strain bacteria, respectively.

Huneau-Salaün, et al., (2009) carried-out a cross-sectional study to identify risk factors for Salmonella sp contamination in French laying hen flocks at the end of the laying period. Five hundred and nineteen flocks were studied between October “2004” and September “2005”. The Salmonella status of the flocks was assessed from 5 faeces samples (pooled faeces samples) from cage flocks, and foot swabs from flocks kept on the floor, and 2 dust samples analysed using a classical bacteriological method. At least one contaminated sample was found in 93 flocks and the apparent prevalence of Salmonella was 17.9% (CI 95%=14.5, 21.3). Prevalence was significantly higher in caged flocks than in on-floor flocks, and logistic-regression models were built for each subpopulation. Associations between farm characteristics, managerial practices and the presence of one or more Salmonella -positive samples in a flock were assessed using a mixed logistic-regression model with a flock-specific random effect. In caged flocks (n=227) the risk of Salmonella contamination increased with flock size, and when delivery trucks passed near poultry-house entrances. The risk of detecting a positive sample was lower with pooled faeces samples than with dust samples. In on-floor flocks (n=292), a higher risk of contamination was associated with multistage management (presence of hens of different ages on the farm); and contamination by Salmonella enteritidis of a previous flock kept on the farm. However, the use of a container for dead bird disposal was a protective factor.

Kaufmann-Bart and Hoop (2009) stated that Between “1992” and “2003”, a period of 12 years after the definitive ban on battery cages in Switzerland, more than 10,000 replacement chicks and laying hens were examined postmortem. There was a significant decrease in the incidence of viral diseases, mostly due to a reduction in Marek's disease, but there was a marked increase in bacterial diseases, particularly since “1999”, mainly due to colisepticaemia in young laying hens. There was a steady decrease in parasitic infections, but the incidence of non-infectious diseases varied from year to year, with no clear trends. There were no significant emerging diseases or economic losses in the alternative housing systems. Vaccination and hygiene were the most effective precautions against infections, and control strategies brought about a marked decline in notifiable diseases, especially for Salmonella enteritidis. Fifteen years after the ban on battery cages in Switzerland, the health and egg production of laying hens is good.

Ricci and Piddock (2010) used a screening procedure, three bacteriophages, ST27, ST29 and ST35 were identified with selective activity for Salmonella enterica serovar Typhimurium (SL1344) but not SL1344 tolC::aph. Over-production of TolC, lead to a lower efficiency of plating (EOP) further suggesting that TolC was the target receptor. Activity against other serovars of Salmonella was observed but not to other species of Enterobacteriaceae. This study provides proof of principle that bacteriophages can be active against the outer membrane protein of tripartite RND efflux pumps and so could be used to reduce the numbers of Salmonella in animals reared for food production.

II. The influence of ambient environmental conditions (Temperature, Relative Humidity, air gases including ammonia and carbon dioxide) on broiler growth and performance.

Chickens and their wastes in poultry houses generate different forms of air pollution, including ammonia, carbon dioxide, methane, hydrogen sulfide and nitrous oxide gases, as well as dust.

Gases such as carbon dioxide, ammonia and methane may accumulate and reach toxic levels if adequate ventilation is not maintained. These different air pollutants may cause risk to the health of both chickens and farm workers. Poor environments normally don’t cause disease directly but they do reduce the chickens’ defenses, making them more susceptible to existing viruses and pathogens (Kling and Quarles, 1974).

Optimal temperature in the poultry houses is required up to 15- 20oC. Environmental temperature was correlated with many measures of performance including feed and water consumption, body weight, egg production, feed conversion, and egg weight (Sterling, et al., 2003). The reduction of egg production under heat stress may have been related to the altered respiratory pattern (Xin, et al., 1987), and in some case of reduction of environmental temperature, birds consume much feed in order to maintain their body heat (Turkoglu, et al., 1997; Howlider and Rose, 1987- 1989).

Relative humidity below 50% and especially as low as 30%, may to some extend aggravate infection and help contagion. Infectious particles stay suspended and viable for longer periods in dry, dusty air; it is mainly for this reason that higher ventilation rates are advised for summer. In poultry houses of laying hen, optimal relative humidity should be between 60-70%. In case of low relative humidity, dust has increased, and in addition to this, the respiratory diseases in the chickens have been seen, (Turkoglu, et al., 1997). Genetically lean broilers appeared to be more resistant to hot conditions, showing enhanced weight gains and better feed and protein efficiencies than their fat-line counterparts despite the fact that the lean birds showed a higher heat increment and increased feathering, (Geraert, et al., 1993a).

From a nutritional point of view, the reduction in growth for a given feed intake has yet to be explained. Indeed, the digestive abilities of the chicks do not seem to be greatly affected by high ambient temperatures neither with respect to amino acids (Zuprizal, et al., 1993; Yoon, et al., 1995) nor metabolizable energy (ME) value Geraert, et al., (1992). Some authors even suggest that ME can be higher under hot climatic conditions, (Keshavarz & Fuller 1980). Chickens exposed to heat are often fatter (Chwalibog & Eggum 1989; Ain Baziz, et al., 1993) which is indicative of a reduced metabolic rate. Humidity and temperature also have an impact on air quality

Aerial ammonia in poultry facilities is usually found to be the most abundant air contaminant. Ammonia concentration varies depending upon several factors including temperature, humidity, animal density and ventilation rate of the facility. Chickens exposed to ammonia showed reductions in feed consumption, feed efficiency, live weight gain, carcass condemnation, and egg production, (Charles and Payne, 1966; Kling and Quarles, 1974; Reece and Lott, 1980).

Studies on the effects of dust in animal housing generally indicate potential for adverse effects on the healthy, growth and development of animals; (Janni, et al., 1985; Feddes, et al., 1992). Respirable aerosol particles within poultry housing have been shown to decrease bird growth, increase disease transfer within flocks, and increase condemnation of meat at processing plants, (Simensen and Olson, 1980).

In broiler houses, ventilation removes moisture and maintains ambient temperature and air quality. During cold weather conditions, ventilation can result in undesirable heat loss from the house. Extra input of energy for heating the building is needed then, resulting in extra CO(2) emissions when fossil fuels are used for this purpose. In such a situation, an air-to-air heat exchanger (HE) might be valuable because it recovers heat by prewarming fresh supply air with warm inside air, (Bokkers, et al., 2010).

Animal production produces a significant component of anthropogenic NH(3) emissions and the National Academy of Sciences concluded that NH(3) emissions estimates from animal feeding operations have not been characterized sufficiently, leading the US Environmental Protection Agency to institute studies in the United States to obtain NH(3) emissions from animal feeding operations under the US Environmental Protection Agency Air Consent Agreement, (Harper, et al., 2010).

Chronic heat exposure and heat stress are causing increasing concern to poultry production in hot climates as well as in temperate countries due to reduced growth performance and increased mortality. Birds, like mammals, are homeotherms, thus they are able to maintain a near-constant body temperature, (Geraert, et al., 1996).

Stoianov, et al., (1977) studied the effect of the temperature and moisture regime on the serum proteins and amino acids in broiler chickens, and they revealed that under the conditions of relatively lower temperatures and higher relative moisture levels the total protein, the albumin, and the gamma-globulin fraction show higher contents. Some changes are also noticeable in the content of the bound amino acids (tyrosin, alfa- and beta-alanine, aspartic acid, and glycin) in the blood sera that are likewise depending on the temperature and moisture regime. The body weight of broilers raised prior to the experiment at 32 degrees C and relative air humidity 70-75 per cent is higher, while the consumption of forage for kilogram weight gain is lower as compared to that with birds raised at higher temperature and lower relative humidity (35-45 and 50 per cent).

Yoder, et al., (1977) determined the influence of air temperature and relative humidity on the severity of airsacculitis produced experimentally using Mycoplasma synoviae (MS) obtained from broiler chickens condemned for airsacculitis. High (31-32 C), medium (19-24 C), and low (7-10 C) air temperatures were studied in conjection with high (75-90%), medium (38-56%), and low (23-26%) relative humidities. Airsacculitis was most extensive (45%) at low temperatures regradless of high or medium humidity. The incidence of airsacculitis was greater (39%) at low humidity than at high humidity (17%) when air temperatures were medium. At high temperature, the trend was toward more airsacculitis (12%) at high humidity than (5%) at low humidity. However, the effect of cold air temperature was more dominant than the effect of relative humidity.

Stoianov, et al., (1978) carried-out an experiment to elucidate the effect of the temperature and moisture regime on the resistance of broiler chickens to an experimental infection with coccidia and how far the prophylactic, anti-coccidial activity of coccidiostatics may be raised or reduced on this basis. They found that the resistance of broiler chickens, grown at a temperature of 32 degrees C and air moisture of 70-75%, to coccidia infection is higher as compared with that of broiler chickens, kept at a higher temperature and lower air moisture.

Teeter and Smith (1986) evaluated the effect of heat stress on acid-base status and the birds' response to supplemental KCl and KCO3. The corn-soybean meal fish-meal basal ration (73% K+) contained more K+ and Cl- than is recommended by the National Academy of Sciences for chicks reared under near optimal conditions (24oC and 55% relative humidity). Chicks reared under continuous thermostress (35oC, 70% relative humidity) exhibited panting phase blood alkalosis (pH of 7.46). Supplementing drinking water with 2% NH4Cl reduced panting phase blood pH to normal values and increased live weight gain (23%) and feed efficiency (7.7%). Supplementing drinking water with 15% KCl also increased (P less than 0.05) live weight gain (46%) and feed efficiency (15.4%) but did not affect (P less than 0.46) blood pH.

Kaĭtazov and Stoianchev (1987): carried out a comparative investigations on the gas composition of air and the productivity of broilers raised in cells and on deep litter in the region of Northeast Bulgaria. The buildings were sized 75X15 X 3.8 m. The air exchange in them was effected through mechanical ventilation at lowered pressure, after the pattern from above--sideways'. The number of birds and the live mass produced per square meter of floor area in the various seasons of the year were calculated at the end of the fattening periods. It was found that by the end of fattening on deep litter the concentration of ammonia varied around the upper admissible threshold, while with fattening in cells it was within the standard range.

Arjona, et al., (1988) conducted an investigation on the effects of heat stress during the 1st wk of life on subsequent mortality resulting from exposure to high environmental temperature and feed restriction just prior to marketing of broiler cockerels. They found that exposing broiler cockerels to mild heat stress for 24 h at 5 days of age can significantly decrease mortality resulting from high environmental temperature later in life.

May, et al., (1990) evaluated the effect of lighting and environmental temperatures on quantity of crop, gizzard and small intestine contents during feed withdrawal. Broilers were on litter with a feeding regimen of 1.5 h on feed and 4.5 h off feed for 1 or 2 days. The withdrawal period began at the end of a 1.5-h feeding period. Lighting reduced crop contents 4 h after feed withdrawal but increased the contents of the small intestine 2 h after feed withdrawal at both temperatures. These results indicated that crop clearance is improved by lighting both before and after cooping.

Hamdy, et al., (1991) evaluated the effects of incubation of 45% versus 55% relative humidity (RH) and early versus late hatching time on heat tolerance of neonatal male and female chicks. Chicks that hatched from eggs incubated at 45% RH were lighter at hatch than chicks that hatched from eggs incubated at 55% RH. Chicks that hatched from eggs incubated at 55% RH lost more body weight and water during heat exposure than those that hatched from eggs incubated at 45% RH. Body weight and water loss during heat exposure of chicks that hatched early and late was similar. It was concluded that chicks that hatched late, i.e., with a short holding period in the hatcher, and coming from eggs incubated at 45% RH had increased heat tolerance in comparison with the other chicks.

Weaver and Meijerhof (1991) examined three levels of relative humidity (RH) (45, 40, to 80, and 75%) and two levels of internal air circulation (7.7 to 9.9 and 17.8 to 24.5 cm/s), with each level replicated and, therefore, forming a 3 x 2 x 2 factorial arrangement of treatments, arrangement of treatments, were imposed as the main effects. Increases in RH significantly increased caking and litter moisture and reduced the percentage of dry matter and the percentage of nitrogen found in the litter. Ammonia levels were more variable but generally increased with increases in RH. The two levels of air movement within the chambers produced less influence on the environment than RH, although the scores for both litter moisture and caking were significantly lower with increased levels of internal air circulation.

Bendheim, et al., (1992) studied the effects of type of feed, ambient temperature and ventilation on ascites on a fast-growing strain of broiler with regard to production parameters. They found that poor ventilation had no effect on the incidence of ascites. Pelleted feed, when compared with the same feed in a mash form, induced a higher incidence of mortality with ascites. Of all these factors, exposure to cold temperatures was the most potent inducer of ascites. For the short-term control of the ascites syndrome, these aspects of husbandry can be changed by the grower to minimalize losses.

Geraert, et al., (1992) studied the effect of high ambient temperature (32o versus 22o C) on dietary ME value was investigated in 32 genetically lean and fat 8-wk-old male chickens. Lean broilers exhibited higher AME and TME values than fat chickens. Hot climatic conditions significantly increased AME and TME values, particularly in leaner birds. Protein retention efficiency was enhanced by selection for leanness and increased with ambient temperature. Correction for nitrogen balance (AME(n) and TMEn) reduced the effect of temperature but lean genotypes still revealed higher TMEn values than fatter ones.

Leenstra and Cahaner (1992) concluded that temperature had a negative effect on breast meat yield. Males were affected more by high temperature than females. A significant interaction between temperature and sex for breast meat yield was caused by a low yield for males at the high temperature. A similar interaction for proportion of abdominal fat was caused by a high fat content in males reared at the high temperature. Slaughter yield and especially yield of breast meat were highest in FC chickens in all comparisons.

Larbier, et al., (1993) investigated the effect of high ambient temperature (32 versus 21o C) between 4 and 6 wk of age on true digestibility of protein (TDP), amino acids (TDAA), and AME value of rapeseed and soybean meals in broilers. The experiment revealed the ambient temperature had no effect on AME values of the raw materials tested for both sexes of broilers. However, high ambient temperature significantly decreased (P < .001) AMEn values of the two rapeseed meals, which could be related to the nitrogen balance. Moreover, TDP and TDAA of two rapeseed and soybean meals tested in this experiment were decreased as the ambient temperature increased from 21o to 32o C. A 12% reduction in TDP value was observed with the rapeseed meals, whereas the diminution was only 5% with the soybean meal.

Debey, et al., (1994) measured the environmental variables in 10 commercial turkey confinement buildings, representing 2 natural ventilation designs during summer and the following winter. Sliding doors spaced at intervals along the walls of 5 of the buildings provided about 35% opening, and continuous wall curtains provided 60 to 80% opening in the other 5 buildings. Ammonia concentration in the air of sliding door-type houses progressively increased during summer and winter sampling periods. A significant effect of building ventilation design on turkey performance was not detected when using mortality, average daily gain, feed conversion, condemnations at slaughter, or average individual bird weight as measures of production.

Gorman and Balnave (1994) studied the relationship between broiler performance and two dietary mineral balance equations was investigated at a high constant ambient temperature (30 degrees C) using a range of 11 salt supplements given to male broiler chicks from 21 to 42 d of age. No relationship was found between broiler performance and either of the two balance equations. Evidence was found that metabolisable anions supplemented in association with mineral cations may have a significant effect on broiler performance.

May (1995) conducted two trials to determine whether heat exposure of neonatal broilers had any effect on their grow-out performance or on their mortality during heat exposure later in life. Broiler chicks, 5 or 6 d old, were exposed to 36.1o C for 24 h in environmental chambers. At 47 d in Trial 1 and at 42 d in Trial 2, the broilers were exposed to 37.8o C for 6.5 h in Trial 1 and 8 h in Trial 2. Early heat exposure did not influence resistance to later heat exposure as measured by mortality. Also, early heat exposure did not affect body weight gain, feed efficiency, or grow-out mortality.

Deaton, et al., (1996) stated that initial brooding temperatures for broilers be reduced to 29.4o C from 32.2o or 35o C. They conducted scheme to see whether the recommended brooding temperature of 29.4o C the 1st wk, 26.7o C the 2nd wk, and 23.9o C the 3rd wk would be satisfactory for broiler production when compared with higher brooding temperature regimens starting at 32.2o or 35o C. the calculation of heat loss based on a commercial setting show an 18% savings in liquified petroleum (LP) gas usage for chicks brooded at 29.4o vs 35 C and a savings of 10% in LP gas usage for chicks brooded at 29.4o vs 32.2 C on a winter day.

Geraert, et al., (1996) investigated the effect of chronic heat exposure (32 degrees, constant) on growth, body composition and energy retention of broiler chickens in relation to age. At 2 and 4 weeks of age, fifty-four male Shaver broiler chickens were allocated to three treatments according to the following design: 22 degrees, ad lib. feeding (22AL); 32 degrees, ad lib. feeding (32AL); and 22 degrees, pair-feeding with the 32 degrees group (22PF). Ambient temperature was kept constant at either 22 or 32 degrees for 2 weeks. Heat exposure decreased feed intake by 14% between 2 and 4 weeks and by 24% between 4 and 6 weeks of age. Even with the same feed intake, chicks gained less weight at 32 degrees than at 22 degrees, 5.5% less in young chickens and 22% less in older ones. Hot environmental conditions thus resulted in decreased feed efficiency; the feed:gain ratio was 2.85 at 32 degrees compared with 2.06 at 22 degrees in 22AL birds for the period 4-6 weeks. Body composition appeared significantly affected by high ambient temperature. Feathering was reduced at 32 degrees in absolute weight but not as a proportion of body weight.

Tegethoff and Hartung (1996) stated that there is an ongoing debate about the optimum stocking density of broiler birds. The figures which are discussed range between 25 kg/m2 and 43 kg/m2. The Ministry for Agriculture, Forestries and Food of Lower Saxony issued a decree which limits the stocking density to 30 kg/m2 in winter and 27 kg/m2 in summer time. Among other rules a day-night-rhythm in lighting has to be installed and the maximum allowable ammonia concentration is limited to 20 ml/m3. Thus, a reduction of bird density to 30 kg live weight per m2 will not have an immediate and strong effect on improving air quality. In particular heat stress in summer remains a problem. Therefore a brief list of measures to reduce heat stress for broilers in included.

Alleman and Leclercq (1997) studied the effect of 2 temperatures (22 degrees and 32 degrees C) and 2 crude protein (CP) levels (160 and 200 g/kg). At 22 degrees C, a reduced CP content did not affect growth rate and breast muscle but slightly increased adiposity and food to gain ratio (FCR). Water consumption was reduced. High temperature reduced growth rate and absolute and proportional breast muscle weight, and increased adiposity and FCR. These effects were more pronounced with the low CP diet. Water consumption was also reduced. It was concluded that reducing CP content did not seem a good way to help broilers to withstand hot conditions. They concluded that amino acids other than lysine, methionine and cystine are probably involved in the detrimental effect of high temperature.

Wathes, et al., (1997) conducted a survey on the concentration and emission rates of aerial ammonia, nitrous oxide, methane, carbon dioxide, dust and endotoxin in 4 examples each of typical UK broiler, cage and perchery houses over 24 h during winter and summer. Mean concentrations of ammonia was ranged from 12.3 to 24.2 ppm while concentrations of methane and nitrous oxide were close to ambient levels. Mass concentrations of aerial dust was ranged from 2 to 10 mg/m3 and 0.3 to 1.2 mg/m3 for inspirable and respirable fractions respectively, while endotoxin concentration was typically about 0.1 microgram/m3. Emission rates of gaseous ammonia were rapid (9.2 g (NH3)/h per 500 kg live body weight) and uniform across the three types of building, while emissions of methane and nitrous oxide were slow.

Kranen, et al., (1998) investigated the effect of genetic constitution (stock) and rearing temperature on the occurrence of hemorrhages in thighs and breasts of water bath stunned broilers and they concluded that high hemorrhage scores in thighs are related to hemodynamic and metabolic adaptations to an increased need for energy and oxygen caused by low rearing temperatures. Hemorrhage scores are not related to stock-dependent differences.

Yahav, et al., (2000) evaluated The effects of relative humidity (rh=40% to 70%) at high ambient temperature (Ta) on the performance of laying hens at different ages (8 to 10 months, Trial 1; and 16 to 18 months, Trial 2). Body weight declined significantly in young and older hens exposed to 60% or 70% and 70% rh, respectively: Food intake declined with increasing Ta, except in the case of older hens exposed to 60% rh, for which it remained relatively constant. Water consumption, however, increased with increasing Ta but the increase was significant in young hens exposed to 70% rh only. They concluded that Ta is the main environmental factor affecting young and older laying hens while the effect of rh is minor.

Sandercock, et al., (2001) examined the effects of acute heat stress (AHS) on indices of respiratory thermoregulation and skeletal muscle damage (myopathy) in broiler chickens at two ages (35 and 63 d of age); the relationships of these responses with changes in meat quality were assessed. Exposure to AHS significantly increased deep-body temperatures, panting-induced acid/base disturbances, and plasma creatine kinase (CK) activities, reflecting heat stress-induced myopathy (HSIM). The extent of the hyperthermia and disturbances in acid/base status and myopathy was significantly (P < 0.05) higher in the older birds. Consistent with AHS-induced alterations in thermoregulatory indices and muscle membrane integrity were changes in breast muscle glycolytic metabolism as indicated by lower muscle pH immediately postslaughter (pHi), increased water loss, and increased incidence of breast muscle hemorrhages. Thus, they concluded exposure to AHS induced disturbances in blood acid/base status and had a detrimental effect upon skeletal muscle membrane integrity. Muscle from broilers exhibited an increased sensitivity to AHS exposure with age. Alterations in antemortem blood acid/base status and muscle membrane integrity induced by AHS were associated (though not necessarily causally) with adverse effects upon breast meat quality.

Guo, et al., (2004) measured indoor air pollutants which included PM(10) (particulate matters with aerodynamic diameter less than 10 microm), total bacteria count (TBC), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO(2)) and sulfur dioxide (SO(2)). The indoor and outdoor concentrations of these target air pollutants at these markets were measured and compared. The effects of air conditioning, temperature/relative humidity variation and different stalls on the indoor air quality were also investigated. The results indicated that all of the average indoor concentrations of PM(10), TBC, CO and NO(2) at the markets were below the Hong Kong Indoor Air Quality Objectives (HKIAQO) standards with a few exceptions for PM(10) and TBC. It was concluded the higher indoor/outdoor ratios demonstrated that the operation of air conditioning had influence on the levels of bacteria at the markets.

Yahav, et al., (2004) stated that Air velocity (AV) is one of the main environmental factors involved in thermoregulation, especially at high ambient temperatures. Air velocity of 2.0 m/sec enables broilers to maintain proper performance together with efficient thermoregulation and water balance under harsh environmental conditions.

Gonzalez and Leeson (2005) conducted two experiments to determine broiler response to dietary protein during short (1 wk) or prolonged (>3 wk) heat stress (HS). In experiment 1, 21-d-old birds were kept at 20.3 degrees C (thermoneutral; TN), 27.3 degrees C (medium temperature; MT), or 31.4 degrees C (high temperature; HT) and fed diets with 18, 20, 23, or 26% CP for 21 d. Each treatment consisted of 2 blocks of 3 replicates of 15 birds. In experiment 2, broilers were fed diets with 18 or 26% CP or fed ad libitum 2 diets with 10 or 30% CP. Level of HS and duration of hyperthermia may determine the response of birds to dietary protein. Discrepancies between the 2 studies in response of birds to protein found after prolonged exposure to HS are discussed in view of the differences in levels of certain amino acids used within each experiment.

Aksit, et al., (2006) conducted two trials to study the effects of heat stress during rearing (trial 1) and crating (trial 2) on broiler stress parameters and fear, breast meat quality, and nutrient composition. The relationships between stress parameters and meat quality traits were also determined. Trial 1 consisted of 3 temperature treatments from 3 to 7 wk: control (temperature was 22 degrees C); diurnal cyclic temperature (temperature was 28 degrees C from 1000 to 1700 h and 22 degrees C from 1700 to 1000 h); and constant high temperature (34 degrees C; temperature was 34 degrees C). In trial 2, broilers from the control and 34 degrees C groups in trial 1 were used. They found that Duration of tonic immobility was neither influenced by rearing and crating temperatures nor associated with meat quality parameters.

Mushtaq, et al.; (2005) determined the effect of increasing levels of Na+ and Cl- above the NRC (1994) recommendations for growing broilers diets (hatching to 28 d) in extremely hot weather. The average maximum and minimum temperatures recorded were 39 and 32 degrees C, respectively. An average relative humidity was 58.2% during the experimental period. Significant dietary effect of Na+ x Cl- was noted only for litter moisture (P < 0.001), dressing percentage (P < 0.05), breast (P < 0.05) and leg (P < 0.001) yields, abdominal fat (P < 0.002), and serum HCO3- (P < 0.001).Birds fed diet containing 0.25% Na+ and 0.30% Cl- performed as well as those fed other diets when the cyclic temperature ranged from 32 to 39 degrees C.

Miles, et al., (2006) provided a unique view of gas flux variation within the house. Collinear factors such as house management, bird size and age, and amount of deposition are significant factors for litter gas flux and should be considered in comprehensive models for emission estimates. The pooled results for the brood and non-brood areas of the house were 1) NH3 flux was greatest in the brood area at d 1, averaging 497 mg/(m2 x h), and had a mean of 370 mg/(m2 x h) in the vacant end of the house; 2) at d 21, the non-brood area had the greater average NH3 flux, 310 mg/(m2 x h), and flux in the brood area was 136 mg/(m2 x h); 3) N2O and CH4 fluxes were <60 mg/(m2 x h); and 4) on d 1, brood CO2 flux was 6,190 mg/(m2 x h) compared with 5,490 mg/ (m2 x h) at the opposite end of the house. On d 21, these values increased to 6,540 and 9,684 mg/(m2 x h) for the brood and non-brood areas. Ammonia flux seemed most affected by litter temperature.

Sandercock, et al., (2006) examined the effects of acute heat stress (2 h at 32 degrees C and 75% RH) on body temperature and indices of respiratory thermoregulation and skeletal muscle function in two divergently selected male grandparent lines of broiler and layer-type chickens at two ages (35 and 63 d), or at a similar body weight (approximately 2.2 kg). Exposure to acute heat stress caused an increase in deep body temperature, panting-induced acid-base disturbances and elevated plasma CK activity in both lines of chicken, an effect that increased with age. The extent of disturbances in acid-base regulation and heat-stress-induced myopathy were more pronounced in the broiler than the layer line at the same age or similar live weights. It was suggested that genetic selection for high muscle growth in broiler lines has compromised their capacity to respond to an acute thermal challenge, leading to detrimental consequences for muscle function. This reduction in heat tolerance may have important implications for bird welfare and subsequent meat quality.

Blahová, et al., (2007) assessed the effect of low environmental temperature on growth, feed conversion, performance and selected biochemical and haematological indicators in broiler chickens. The decrease in air temperature since the 22nd day of growth influenced significantly (p < 0.05) the level of total proteins, uric acid, phosphorus (in female broiler chickens), glucose (in male broiler chickens), haemoglobin (in female broiler chickens) and liver weight (in male broiler chickens). The temperature influenced significantly (p < 0.01) the level of triiodothyronine, haemoglobin (in male broiler chickens), haematocrit, abdominal fat content (in male broiler chickens), and heart weight too.

Lu, et al., (2007) studied the effects of chronic heat stress on growth, proportion of carcass and fat deposition, and meat quality in 2 genetic types of chickens. The study indicated that the impact of heat stress was breed dependent and that BJY chickens showed higher resistance to high ambient temperature, which could be related to their increased feed efficiency and deposition of abdominal fat under heat exposure.

Ahmad, et al., (2008) evaluated the effect of water supplementation of KCl on performance of heat-stressed Hubbard broilers. They found that enhanced physiological adaptation with 0.6% KCl was evidenced by a more favorable pH during the panting phase in the present study. These findings demonstrated a possibility of better broiler live performance through KCl supplementation under conditions of severe heat stress (35 to 38 degrees C).

Ahmad, et al., (2009) determined the effects of varying dietary electrolyte balance (DEB) on growth performance and physiological responses in broiler chicks reared during hot summer months (26.1-37.5 degrees C). The average minimum and maximum room temperatures recorded from 14 to 42 days of age were 26.1 and 37.5 degrees C, respectively, with relative humidity ranging from 51% to 55%. The study concluded that overall better performance was recorded with DEB 50, 150 and 250mEq/kg. These results indicated that single optimal DEB value could not be recommended to combat heat stress in broilers.

Al-Aqil, et al., (2009) determined the effects of two types of housing systems and early age feed restriction on stress and fear reactions, and performance in broiler chickens raised in a hot, humid tropical climate. The results suggested that although OH birds had poorer performance and higher level of stress than CH, the former were less fearful. Although FR had negligible effect on growth performance, the regimen alleviated both stress and fear reactions in broilers.

Abdollahi, et al., (2010) investigated the influence of conditioning temperature on the performance, nutrient utilisation and digestive tract development of broilers fed on maize- and wheat-based diets was examined up to 21 d of age. While the effects of conditioning temperature on body-weight gain and feed intake of broilers to 21 d of age differed depending on the grain type, feed per body-weight gain was adversely affected by higher conditioning temperatures.

Aksit, et al., (2010) evaluated the effects of brooding temperature on intestinal development, oxidative organ damage, and performance of chicks acclimated to high temperature during incubation. The effects of acclimation and brooding temperatures on slaughter weights of broilers under heat stress were also investigated. They found that although higher brooding temperatures had no effect on body weights of INC(H) chicks during the brooding period, those broilers may able to cope better with heat stress.

Bokkers, et al., (2010) analyzed effects of on-farm use of an heat exchange (HE) on broiler performance, energy use, and CO(2) emission by comparing production cycles with and without an HE, and to inventory the experiences of farmers using an HE. The use of an HE tended to increase daily weight gain (56 vs. 55, SEM 0.3 g/d; P = 0.07), but did not affect other performance variables. Based on 13 farms, gas use was reduced by 38% (P < 0.01) after installing an HE. Based on 3 farms only, an HE did not affect electricity use, total energy use, or calculated CO(2) emission. The use of an HE reduced gas use and has the ability to improve broiler weight gain but had no effect on other broiler performance variables. Effects on CO(2) emission were unclear.

Drake, et al., (2010) conducted a longitudinal study that included over 335,500 birds from 22 free range and organic laying farms. Accelerated failure time models and proportional hazards models were used to examine the effects of a wide range of factors (management, environment and bird) on development of substantial feather damage in layer. Particular emphasis was placed on risk factors during rear and on practices that could feasibly be changed or implemented. Factors that were associated with earlier onset of severe feather damage included the presence of chain feeders, raised levels of carbon dioxide and ammonia, higher sound and light levels, particularly in younger birds. Increased feather damage (even very slight) in birds at 17-20 weeks of age was also highly predictive of the time of onset of severe feather damage during lay.

Harper, et al., (2010) obtained an additional broiler NH(3) emissions estimates using a backward Lagrangian stochastic technique. This technique uses NH(3) concentrations measured upwind and downwind of the farm, wind observations, and atmospheric dispersion model calculations to obtain whole-farm emissions. Ammonia emissions were low at bird placement and increased steadily after about the third week of growth. At the end of the flock (47 d, ~297,000 birds), cumulative emissions for the flock cycle period were 0.016 kg of NH(3). total flock wintertime and summertime (flock cycle plus between-flock) NH(3) emissions from this farm represented 7.8 and 8.3% of feed N as NH(3)-N, respectively, or an annual average of 8.1%.

Ni, et al., (2010) evaluated the characteristics of NH(3) and CO(2) releases from layer hen manure using 4 manure reactors (122 cm tall, 38 cm internal diameter), which were initially filled with 66 cm deep manure followed by weekly additions of 5 cm to simulate manure accumulation in commercial layer houses. The average daily mean (ADM) NH(3) and CO(2) release fluxes for the 4 reactors during the entire study were 1615 +/- 211 microg/s.m(2) (ADM +/- 95% confidence interval) and 100 +/- 03 mg/s.m(2), respectively. The daily mean NH(3) and CO(2) releases in individual reactors varied from 352 to 6791 microg/s.m(2) and from 66 to 205 mg/s.m(2), respectively. Fresh manure had greater NH(3) release potential than the manure in the reactors under continuous ventilation. Manure with higher contents of moisture, total nitrogen, and ammonium in the 4th weekly addition induced 11 times higher NH(3) and 75% higher CO(2) releases immediately after manure addition compared with pre-addition releases.

Wang, et al., (2010) evaluated the effectiveness of in-house ozonation within the public health standard limit (0.1 parts per million [ppm]) for mitigating ammonia (NH3) concentrations inside commercial broiler houses, all other operational parameters including feed, broiler strain, age and number of broilers, and ventilation system were the same among four houses. NH3 and carbon dioxide (CO2) concentrations in the treatment and control houses were measured for a minimum of 48 hr/week throughout the five flocks of 8 or 9 weeks each. The evaluation indicated that there was no statistical evidence to suggest that the ozone treatment has any effect on average NH3 concentrations in these chicken houses.

Calvet, et al., (2011) measured ammonia, carbon dioxide, methane, and nitrous oxide concentrations and emissions in a commercial broiler farm Gas concentrations were measured using a photoacoustic gas monitor, whereas the ventilation flow was evaluated by controlling the operation status of each fan. All gas emissions increased with bird age. Ammonia emission rates averaged 19.7 and 18.1 mg/h per bird in the summer and winter, respectively, and increased with indoor temperature (r(2) = 0.51 in summer; r(2) = 0.42 in winter). Average CO(2) emission rates were 3.84 and 4.06 g/h per bird, CH(4) emission was 0.44 and 1.87 mg/h per bird, and N(2)O emission was 1.74 and 2.13 mg/h per bird in summer and winter, respectively.

Poultry litter or broiler litter is commonly recovered from many poultry operations and recycled as an organic fertilizer or as a feed supplement for ruminants (Rankins, et al., 2002; Harapas, et al., 2003).

Poultry litter may or may not have been aged or composted by the time it arrives on the vegetable farm. It could be used immediately or stored for some months, sometimes in close proximity to maturing vegetable crops. Practices differ widely among farms and between crops on an individual farm. Poultry litter is known to contain bacteria that have the potential to cause human illness, such as Salmonella and Staphylococcus;(Martin, et al., 1998; Terzich, et al., 2000), and contamination of fresh product with manure has been implicated as the cause of numerous bacteriological food poisoning outbreaks; (Brackett; 1999; Doyle and Erickson, 2008). Although the use of poultry litter in commercial vegetable farming has rarely been associated with food-borne illnesses, heightened consumer awareness of food safety issues has increased the scrutiny of on-farm management practices in many countries.

Poultry litter is a relatively hostile environment for the persistence of pathogens because it is typically dry, heats up readily, and generates ammonia gas. Deep stacking or ensiling poultry litter is commonly recommended as a pretreatment to improve its safety and palatability as a feed for ruminants; (Capucille, et al., 2004; Bush, et al., 2007). Bush, et al. (2007) showed that despite the wide variation of temperature within the stacks, Salmonella was eliminated in 98.7% of all inoculated sites. Furthermore, Salmonella organisms were reduced by at least log5 in the remaining sites where it was still viable. Himathongkham and Riemann, (1999) showed that E. coli O157:H7 and L. monocytogenes were able to multiply by as much as 100-fold for a period of 2 d in fresh chicken manure at 20°C while Salmonella typhimurium densities remained stable.

Litter can be considered one of the most favorable media for the growth and transmission of Salmonella, depending on water activity (Aw), and moisture content (MC). High Aw values (0.90-0.95) were associated with flocks positive for Salmonella; while low Aw values (0.79-0.84) were associated with flocks negative for Salmonella; and transition Aw values (0.85-0.89) were associated with flocks having increased risk for the presence of Salmonella;( Carr, et al., 1995). Contaminated poultry litter, serving as a reservoir for Salmonella, can be linked to both food safety concerns when contaminated birds enter processing plants and environmental concerns when used as fertilizer.

The survival of Salmonella in poultry house environment is dependent on both physical and chemical factors such as temperature, water activity (Aw) or equilibrium RH (ERH), moisture content, and pH. Whenever extrinsic factors fall outside the optimum range for microbial growth and survival, these factors can cause cellular damage. Depending on the severity of the stress factors, growth can be inhibited or cell death can occur, (Farkas, 2001).

Williams and Benson (1978) determined the persistence of Salmonella typhimurium in poultry feed and litter contaminated with a large no. of cells stored at different temperature degree (11oC, 25oC or 38 oC). The organisms survived best at the two lower temperatures. Persistence was as follows: at 11 C, at least 18 months in both feed and litter; at 25 C, 16 months in feed and 18 months in litter; and at 38 C, about 40 days in feed and only 13 days in litter. Hence, samples of feed and litter collected for bacteriologic examination should be stored at low temperatures.

Nashed (1986) investigated the viability of Salmonella typhimurium in feed and litter contaminated with this germ, at different temperatures. The organism remained viable at 37 degrees C in feed up to 6 weeks, in litter for 2 weeks, at room temperature in the feed up to 71 weeks in the litter up to 78 weeks, and at 7 degrees C in feed and litter up to 79 weeks. Recommendations are given for the control of salmonellosis by referring to the sources and possibilities of contamination.

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