The influences of SE infection on layers' production performance, egg quality and blood biochemical indicators

Comprehensive evaluation of treating drinking water for laying hens using slightly acidic electrolyzed water

Slightly acidic electrolyzed water (SAEW) is well-known for its highly potent antibacterial properties and safe residue-free nature. In this study, a comprehensive evaluation was conducted on 2 disinfection methods for waterline cleaning in poultry houses: (1) continuously add SAEW into the waterline and (2) the conventional waterline disinfection method, which includes regular use of high-concentration chemical disinfectant for soaking the waterline and flushing with water. The evaluation focused on the effects of these methods on bacteria levels in laying hens' drinking water, the fecal normal rate of laying hens, egg quality, as well as the economic costs and water footprint associated with each method. The results show that the inhibition rate of the control group was 52.45% to 80.36%, which used 1500 mg/L sodium dichloroisocyanurate (DCCNa) for soaking and then flushing with water. The bacterial levels in the waterline returned to pre-treatment levels 26 h after cleaning. However, the experimental group with an available chlorine concentration (ACC) of 0.3 mg/L SAEW showed a higher inhibition rate (99.90%) than the control group (P < 0.05) and exhibited a sustained antimicrobial effect. Regarding eggshell thickness, eggshell strength, and Haugh units of the egg, there were no significant differences between the experimental and control groups. However, the experimental group had higher egg weight and darker yolk color (P < 0.05) than those of the control group. Besides, the experimental group exhibited a higher fecal normal rate and a lower water footprint than those of the control group. Hence, SAEW represents a favorable choice for disinfecting drinking water in poultry houses due to its ease of preparation, lack of residue, energy efficiency, and efficient antibacterial properties. To ensure adequate sanitation, it is recommended to incorporate SAEW with an ACC of 0.3 mg/L into the daily management of the drinking water system for laying hens.

Molecular characteristics and pathogenicity of a novel chicken astrovirus variant

It is well-established that the genetic diversity, regional prevalence, and broad host range of astroviruses significantly impact the poultry industry. In July 2022, a small-scale commercial broiler farm in China reported cases of growth retardation and a 3% mortality rate. From chickens displaying proventriculitis and pancreatitis, three chicken astroviruses (CAstV) isolates were obtained and named SDAU2022-1-3. Complete genomic sequencing and analysis revealed the unique characteristics of these isolates from known CAstV strains in ORF1a, ORF1b, and ORF2 genes, characterized by an unusually high variability. Analysis of amino acid mutations in ORF1a, ORF1b, and ORF2 indicated that the accumulation of these mutations played a pivotal role in the emergence of the variant strain. Inoculation experiments demonstrated that affected chickens exhibited liver and kidney enlargement, localized proventricular hemorrhage, and a dark reddish-brown appearance in about two-thirds of the pancreas. Histopathological examination unveiled hepatic lymphocytic infiltration, renal tubular epithelial cell swelling, along with lymphocytic proventriculitis and pancreatitis. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis indicated viremia and viral shedding at 3 days post-infection (dpi). The proventriculus displayed the highest viral loads, followed by the liver, kidney, duodenum, and pancreas. Liver parameters (AST and ALT) and kidney parameters (UA and UN) demonstrated mild damage consistent with earlier findings. While the possibility of new mutations in the ORF2 gene of CAstV causing proventriculitis and pancreatitis warrants further investigation, these findings deepen our comprehension of CAstV's pathogenicity in chickens. Additionally, they serve as valuable references for subsequent research endeavors.

Effect of classical music on growth performance, stress level, antioxidant index, immune function and meat quality in broilers at different stocking densities

High-stocking density is one of the factors that can easily cause oxidative stress and inflammatory reaction of broilers. Currently, music therapy has been proposed to help animals relieve stress to some extent. However, it is still unclear whether classical music can alleviate stress in broilers at high stocking densities. Hence, this study aimed to investigate the effects of classical music on growth performance, stress level, antioxidant index, immune function and meat quality of broilers under different stocking densities. A total of 540 one-day-old broilers with similar body weight were randomly divided into 6 treatment groups, with 6 replicates per group, which included two feeding environments (with/without classical music) and three stocking densities (15.5, 17.9, and 20.3 birds/m2), thereby making a 2 × 3 factorial arrangement. The results showed as follows: increasing stocking density decreased the average daily feed intake and average daily gain (ADG), increased feed-to-gain ratio (F/G) and mortality of broilers. Moreover, increased density resulted in an increase in serum corticosterone (CORT) and adrenocorticotropic hormone (ACTH) levels. Increasing stocking density decreased spleen and bursal indices, serum immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM) levels. Increasing stocking density elevated serum malondialdehyde (MDA) and decreased catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) activities. Increasing stocking density decreased serum total protein (TP) levels and increased total cholesterol (TC) and glucose (GLU) levels. Additionally, increasing stocking density decreased the cooking liss of pectoralis and increased the L*24h value of pectoralis. Meanwhile, playing classical music for broilers increased their ADG and decreased F/G, and decreased serum CORT, ACTH, GLU content. In addition, the bursa of Fabricius index, serum IgA and IgG contents as well as the a*24h value of pectoralis was increased under the music therapy. In conclusion, high-stocking density (20.3 birds/m2) harmed the growth performance and health of broilers, and the classical music stimulus ameliorated the negative effects to some extent.

Pathogenicity of duck circovirus and fowl adenovirus serotype 4 co-infection in Cherry Valley ducks

Duck circovirus (DuCV) is one of the most prevalent infectious viruses in the duck industry in China. Although the clinical symptoms vary, it often causes immunosuppression in the host and leads to secondary infection with other pathogens. Fowl adenovirus serotype 4 (FAdV-4) mainly infects chickens and causes hydropericardium hepatitis syndrome. However, the incidence of infection in ducks has increased in recent years, and the phenomenon of mixed infection with DuCV is very common, resulting in more severe clinical morbidity. However, there is no systematic study evaluating the presence of mixed infection. To explore the synergistic pathogenicity of DuCV and FAdV-4 co-infection in Cherry Valley ducks, a comparative experiment was established between DuCV and FAdV-4 co-infection and single infection animal models. It was found that DuCV and FAdV-4 co-infected ducks showed more pronounced clinical signs of pericardial effusion, hepatitis and immunosuppression; more severe tissue damage in target organs; and more significant levels of viral load, biochemical indicators and immune indicators in various organs compared with Cherry Valley ducks infected with just one virus. The results showed that co-infection with DuCV and FAdV-4 may promote greater viral replication, causing more severe tissue damage and immunosuppression than infection with just one virus. Therefore, the monitoring and prevention of the two viruses should be strengthened clinically, with a particular focus on the potential harm of DuCV as it carries the highest infection rate.

Lonicera flos and Cnicus japonicus extracts improved egg quality partly by modulating antioxidant status, inflammatory-related cytokines and shell matrix protein expression of oviduct in laying hens

This study was conducted to investigate the effects of Lonicera flos and Cnicus japonicus extracts (LCE) on the laying performance, egg quality, morphology, antioxidant status, inflammatory-related cytokines, and shell matrix protein expression of oviduct in laying hens. A total of 1,728 Roman Pink laying hens aged 73-wk-old were randomly assigned into 4 groups (18 replicates/group, 24 layers/replicate) fed basal diets supplemented with 0, 300, 500, and 1,000 mg of LCE per kg of diet, respectively. The trial lasted for 11 wk, including 2-wk adjustment period and 9-wk testing period. The results indicated that laying hens fed diets supplemented with LCE linearly increased egg weight, yolk color and shell thickness at wk 78 and albumen height, Haugh unit and shell thickness at wk 83 (P < 0.05). At wk 78, LCE groups linearly affected the hydrogen peroxide content in magnum (P < 0.05) and 300 mg/kg LCE groups had the highest catalase activity in isthmus (P < 0.05). At wk 83, LCE groups linearly reduced (P < 0.05) hydrogen peroxide content in the magnum and isthmus and malondialdehyde content in the uterus whereas increased catalase activity in isthmus (P < 0.05). Furthermore, LCE levels quadratically affected glutathione peroxidase activity in isthmus at wk 83 (P < 0.05). At wk 78, the mRNA expressions of inducible nitric oxide synthase and interferon-γ in isthmus and ovalbumin and ovocleidin-116 in uterus had linear effects in response to LCE levels (P < 0.05) and 1,000 mg/kg LCE group had the lowest mRNA expression of interleukin-6 in magnum (P < 0.05). At wk 83, LCE supplementation linearly decreased the mRNA expression of interleukin-1β, interferon-γ and tumor necrosis factor-α in magnum and tumor necrosis factor-α and inducible nitric oxide synthase in uterus (P < 0.05). It is concluded that LCE improved egg quality partly by modulating antioxidant status, inflammatory-related cytokines and shell matrix protein expression of oviduct in laying hens.

Effects of Glyceryl Monolaurate on Production Performance, Egg Quality, Oviduct Cytokines and Intestinal Microflora of 66 Weeks Old Laying Hens

The principal purpose of this research was to study the effects of glycerol monolaurate (GML) on the production performance; egg quality; health state of the oviduct, ovary and ileum; and gut microbiota of laying hens in the later stage. The laying hens were randomly assigned to two groups: a control group and an experiment group, for which 1000 mg/kg of GML was added to a control diet. The results showed that GML increased the laying rate, average egg weight, albumen height, yolk color and Haugh unit and decreased the feed conversion ratio and defective eggs (p < 0.05). GML increased the intestinal villi height and the ratio of villus height to crypt depth (p < 0.05). Moreover, GML improved the contents of cytokines in the oviduct, ovary and ileum mucosa; ameliorated the expression of TLR2, TLR4, MyD88, IL-4, IL-1β and TNF-α; and increased the expression of Occludin and Muc-2 in the ileal mucosa. The supplementation of GML increased the volatile fatty acids in the cecal contents, such as acetic acid and propionic acid, and up-regulated Bacteroides (p < 0.01) and Alistipes (p < 0.05) richness in the cecal contents. In summary, GML improved production performance, egg quality and immunity; ameliorated the health status of the oviduct, ovary and ileum; enhanced the intestinal barrier function; improved the content of intestinal volatile fatty acids; and regulated the abundance of cecal flora.

Isolation and Pathogenicity of a Novel Goose Astrovirus from Overfed Adult Landaise Geese in China

Goose astrovirus (GAstV) is an important pathogen causing visceral gout and high mortality in goslings, which has broken out and spread across China. In 2021, a disease characterized by urate deposition on the visceral surface and 30% mortality occurred in commercial adult Landaise geese in Zhejiang Province, China. A systematic study identified an infecting astrovirus, designated ZJCX, that was efficiently isolated from a diseased goose with a chicken hepatocellular carcinoma cell line (LMH). In contrast to other GAstVs originating from goslings, ZJCX caused cytopathogenic effects in LMH cells, and the crystalline arrangement of viral particles was observed through transmission electron microscopy. Indeed, phylogenetic analysis and nucleotide homology comparison revealed that ZJCX isolate belongs to the genotype II cluster of GAstVs and displays 97.8-98.4% identity with other GAstV II strains. However, several specific mutations occurred in the polyprotein and capsid protein regions. Moreover, a pathogenicity assessment of ZJCX with a gosling model was conducted, and typical visceral gout was reproduced and led to 18% mortality. The viral loads of ZJCX in the blood, kidney, and liver were detected with specific primers after inoculation, which demonstrated that the kidney and liver presented viral loads peaking at seven days post-inoculation (dpi). Biochemical parameter examination showed that AST, ALT, γ-GT, UA, and BUN levels were significantly increased by GAstV, whereas body weight was reduced. Overall, this study indicated that the GAstV isolate could infect adult geese, and the results regarding the viral loads and biochemical parameters induced by ZJCX provide insight into GAstV pathogenicity.

Dietary selenium sources alleviate immune challenge induced by Salmonella Enteritidis potentially through improving the host immune response and gut microbiota in laying hens

The aim of this study was to evaluate the effects of different selenium (Se) sources on the immune responses and gut microbiota of laying hens challenged with Salmonella enteritidis (S. Enteritidis). A total of 240 45-week-old layers were randomly divided into eight groups with six replicates per group according to a 4 × 2 factorial design, including a blank diet without Se supplementation (CON group) and three diets with 0.3 mg/kg Se supplementation from sodium selenite (IS group), yeast Se (YS group), and selenium-enriched yeast culture (SYC group), respectively. After 8 weeks of feeding, half of them were orally challenged with 1.0 ml suspension of 109 colony-forming units per milliliter of S. Enteritidis daily for 3 days. The serum was collected on days 3, 7, and 14, and the cecum content was collected on day 14 after challenge. There was no significant difference in laying performance among the eight groups before challenge. The S. Enteritidis challenge significantly decreased the laying performance, egg quality, GSH-Px, IgG, and IgM and increased the ratio of feed and egg, malondialdehyde (MDA), Salmonella-specific antibody (SA) titers, IL-6, IL-2, IL-1β, and INF-γ. However, SYC increased the level of GSH-Px and IgG and decreased IL-6, while YS decreased the level of IL-2 and IL-1β. What is more, Se supplementation decreased the SA titers to varying degrees and reduced the inflammatory cell infiltration in the lamina propria caused by S. Enteritidis infection. In addition, the S. Enteritidis challenge disrupted the intestinal flora balance by reducing the abundance of the genera Clostridium innocuum, Lachnospiraceae, and Bifidobacterium and increasing the genera Butyricimonas and Brachyspira, while Se supplementation increased the gut microbial alpha diversity whether challenged or not. Under the S. Enteritidis challenge condition, the alteration of microbial composition by the administration of different Se sources mainly manifested as IS increased the relative abundance of the genera Lachnospiraceae and Christensenellaceae, YS increased the relative abundance of the genera Megamonas and Sphingomonas, and SYC increased the genera Fusobacterium and Lactococcus. The alteration of gut microbial composition had a close relationship with antioxidant or immune response. To summarize, different Se sources can improve the egg quality of layers challenged by S. Enteritidis that involves elevating the immunity level and regulating the intestinal microbiota.

Vitamin K alleviates bone calcium loss caused by Salmonella Enteritidis through carboxylation of osteocalcin

Background

The present study aimed at evaluating the effect of vitamin K (VK) supplementation on bone health of laying hens challenged by Salmonella Enteritidis.

Methods

A total of 80 32-week-old double negative salmonella-free brown-egg laying hens were randomly assigned to 4 treatments with 20 replicates each (1 bird per replicate) according to a 2 × 2 factorial design with 2 dietary VK supplementation levels [0 mg/kg (VK0) vs 2 mg/kg VK (VK2) and 2 challenge treatments [Salmonella Enteritidis (SE) vs physiological saline solution (PS)]. During the last 3 days of week 43 of age, birds of both VK treatments were either orally challenged with 1.0 mL suspension of 10⁹ cfu/mL S. Enteritidis daily or received the same volume of PS.

Results

The laying rate, daily egg mass, tibia strength, CT, cOC and cOC/(cOC + ucOC) of VK2 treatment increased (P < 0.05) in contrast to VK0, however, the medullary area and ucOC of VK2 treatment decreased (P < 0.05) in contrast to VK0. Mortality, medullary area, serum Ca content of SE treatments increased (P < 0.05) in contrast to PS treatments. In both SE treatments, the decrease (P < 0.05) in birds’ tibia strength was associated with higher (P < 0.05) Ca levels in serum. There is an interaction (P < 0.05) between SE challenge and VK levels with regard to tibia strength and serum Ca levels. At week 42, serum CT was positively correlated with cOC (R = 0.99, P = 0.009); at week 44, tibia strength was positively correlated with BMD (R = 0.95, P = 0.045), but negatively correlated with medullary area (R = − 0.98, P = 0.018).

Conclusions

VK (2 mg/kg) supplementation to diets of laying hens can enhance bone strength under challenge situations with Salmonella Enteritidis. Medullary area has proven to be a sensitive biomarker for bone calcium loss caused by SE infection.

Effects of Essential Oils-Based Supplement and Salmonella Infection on Gene Expression, Blood Parameters, Cecal Microbiome, and Egg Production in Laying Hens

One of the main roles in poultry resistance to infections caused by Salmonella is attributed to host immunity and intestinal microbiota. We conducted an experiment that involved challenging Lohmann White laying hens with Salmonella Enteritidis (SE), feeding them a diet supplemented with an EOs-based phytobiotic Intebio^®. At 1 and 7 days post-inoculation, the expression profiles of eight genes related to immunity, transport of nutrients in the intestine, and metabolism were examined. Cecal microbiome composition and blood biochemical/immunological indices were also explored and egg production traits recorded. As a result, the SE challenge of laying hens and Intebio^® administration had either a suppressive or activating effect on the expression level of the studied genes (e.g., IL6 and BPIFB3), the latter echoing mammalian/human tissue-specific expression. There were also effects of the pathogen challenge and phytobiotic intake on the cecal microbiome profiles and blood biochemical/immunological parameters, including those reflecting the activity of the birds' immune systems (e.g., serum bactericidal activity, β-lysine content, and immunoglobulin levels). Significant differences between control and experimental subgroups in egg performance traits (i.e., egg weight/number/mass) were also found. The phytobiotic administration suggested a positive effect on the welfare and productivity of poultry.

Pathogenicity of novel goose-origin astrovirus causing gout in goslings

Background

A novel goose-origin astrovirus (GoAstV) has broken out across China in recent years, causing gout in goslings with a mortality rate of around 50%. However, our understanding of the dynamic distribution, tissue tropism and pathogenesis of GoAstV is incomplete. In order to assess its pathogenicity, one-day-old goslings were inoculated separately with GoAstV via oral and subcutaneous injection routes.

Results

Clinical symptoms, gross and microscopic lesions, blood biochemical parameters and viral loads were detected and recorded for 20 days after infection. Typical gout was observed in experimental goslings. GoAstV can be replicated in tissues and cause pathological damage, especially in the kidney, liver, heart and spleen. Virus-specific genomic RNA was detected in blood, cloacal swabs and all representative tissues, and virus shedding was detected up to 20 days after inoculation, suggesting that GoAstV has a wide tissue tropism and spread systematically after inoculation. The viral copy numbers examined in kidney were the highest, followed by spleen and liver.

Conclusion

This experiment determined the accurate value of viral loads and biochemical indicators of GoAstV-induced goslings. These findings increase our understanding of the pathogenicity of GoAstV in goslings and provide more reference for future research.

Novel goose-origin astrovirus infection in geese: the effect of age at infection

Since 2017, a serious infectious disease characterized by visceral gout has emerged in China's main goose-producing regions. The disease has caused huge economic losses to China's goose industry. In our previous study, we determined that the pathogen causing gout in goslings is a novel goose-origin astrovirus, designated as AStV/SDPY/Goose/1116/17 (AStV-SDPY) strain. To investigate the effect of host age on the outcome of novel goose-origin astrovirus infection, 200 1-day-old healthy goslings were selected to be experimentally infected at 1, 5, 15, 25, and 35 D of age. It was shown in experimental infection that the AStV-SDPY strain was highly pathogenic in goslings aged 1 to 15 D, causing growth repression, severe visceral urate deposition, and even death, whereas goslings infected at 25 and 35 D of age showed mild symptoms. Histopathologic examination indicated that lesions occurred mainly in the kidney and liver of infected goslings, which is correlated to the severity of clinical signs and gross lesions. Viral RNA was detected in all representative tissues, and virus shedding was detected continuously within 15 D after inoculation. Higher viral copy number, especially in vital organs such as the liver and kidney, was developed in the goslings infected at 1 to 15 D of age than older geese. In addition, clinical chemistry and inflammatory cytokines showed that younger geese are more sensitive to AStV infection. Overall, our study demonstrates that the pathogenicity of AStV-SDPY in goslings is partly associated with the age of infection, laying a foundation for further study of the pathogenic mechanism of this virus.

Protective Effect of Vitamin E on laying performance, antioxidant capacity, and immunity in laying hens challenged with Salmonella Enteritidis

Vitamin E (VE) has proven to function as potent lipid-soluble antioxidant, a signaling molecule, and a regulator of the immune system. The objective of the study was to assess the protective effect of VE on laying performance, antioxidant capacity, and immunity in laying hens exposed to Salmonella Enteritidis (SE). A total of 80 32-week-old salmonella-free double negative Hy-Line brown laying hens were randomly assigned to 4 treatments with 20 replicates each (1 bird per replicate) according to a 2 × 2 factorial design with 2 VE supplementation levels [0 IU/kg (VE0) vs. 30 IU/kg (VE30)], and 2 challenge treatments [SE vs. physiological saline solution (PS)]. During the last 3 D of week 43 of age, birds were orally challenged with 1.0 mL suspension of 109 cfu/mL S. Enteritidis daily, whereas the birds of negative treatments (VE0) received the same volume of PS. The egg mass of VE0 treatment decreased (P < 0.05) in contrast to VE treatment after challenge. The serum concentrations of interleukins (IL-1β and IL-6) and malondialdehyde (MDA) levels of SE treatments increased (P < 0.05) at week 44 and week 46, respectively. In both VE30 treatments, the decrease (P < 0.05) in birds' mortality was associated with higher IgA, IgG, IgM concentrations at week 44, and higher IgA, IgM concentrations at week 46. There is an interaction (P < 0.05) between SE challenge and VE levels with regard to feed conversion, daily egg mass, and serum MDA, IgA, and IgM levels. It can be concluded that supplemental VE (30 IU/kg) in diets for laying hens may alleviate oxidative and immune stress due to SE challenge.

Pathogenicity of fowl adenovirus serotype 4 (FAdV-4) in chickens

Hepatitis-hydropericardium syndrome (HHS) is an acute infectious disease caused by fowl adenovirus serotype 4 (FAdV-4), which mainly infects broilers aged 3-5 weeks. In March 2018, a pathogenic disease, which was characterized by symptoms similar to HHS, broke out in 10-day-old broiler flocks in Shandong province. In this study, a strain of FAdV-4 (SDSG) was isolated from naturally infected broilers. To assess its pathogenicity, 10-day-old and 20-day-old specific pathogen-free (SPF) chickens were inoculated separately with the FAdV-4 virus fluid via oral and intramuscular injection routes. The results show that typical hydropericardium and hepatitis were observed in experimental chickens. The titer levels of the virus antibody and the levels of inflammatory cytokines were upregulated, which may be caused by the infection and innate immune response. The detection of viral load showed that the presence of virus was detected in multiple organs, in which the liver contained the highest concentration of viral DNA, and the virus content in the intramuscular injection group was higher than that of the oral injection group. In summary, these findings increase our understanding of the pathogenicity of FAdV-4 (SDSG) in chickens. The established model will be valuable for anti-viral drug testing and vaccine evaluation, which can prevent and reduce the spread of HHS in the poultry industry.

Pathogenicity of fowl adenovirus (FAdV) serotype 4 strain SDJN in Taizhou geese

Hydropericardium hepatitis syndrome (HHS) is a fatal disease in chickens, mainly caused by fowl adenovirus serotype 4 (FAdV-4). Since June 2015, HHS has appeared in many provinces in China. The disease has spread from broilers to laying hens, breeders and Cherry Valley ducks, seriously endangering the health of the poultry industry in China. In July 2016, an infectious disease was noticed in a goose farm in Jinan, Shandong Province, China, and hydropericardium was the main finding in post mortem investigations. In the actual study, we isolated a FAdV-4 strain from the livers of naturally-infected goslings and designated it as SDJN. We first evaluated its pathogenicity by inoculating Taizhou geese at 10, 20, and 30 days of age with 10^-7.15EID₅₀/0.2 ml doses of the SDJN strain in 1 ml allantoic fluid via subcutaneous injection or oral infection. Clinical signs and pericardial effusion appeared in geese infected subcutaneously at 10 days of age, whereas 20- and 30-day-old geese were not susceptible to FAdV-4. The results of real-time PCR showed that the replication ability of FAdV-4 in geese correlated with the age. Furthermore, results from clinical chemistry showed that FAdV-4 damaged the liver and kidney in geese and the results paralleled viral load and gross lesions. Consequently, FAdV-4 was pathogenic in geese, and the pathogenicity was related to age and mode of infection. This study is the first experimental infection of FAdV-4 in geese, which will provide a basis for further understanding of the disease. RESEARCH HIGHLIGHTS Pathogenicity tests with a FAdV-4 were conducted in geese, which included data on clinical signs, gross pathology, histopathology, clinical chemistry and viral load. FAdV-4 could replicate in geese and HHS was successfully induced. Pathogenicity of FAdV-4 in geese was related to the age and routes of infection.

Serological and Pathogenic Analyses of Fowl Adenovirus Serotype 4 (FAdV-4) Strain in Muscovy Ducks

Hydropericardium hepatitis syndrome (HHS) is a lethal disease caused by Fowl adenovirus serotype 4(FAdV-4) that mainly infects 3- to 6-week-old broiler chicks. In 2015, an infectious disease characterized similar symptom to HHS in broilers outbroke in commercial duck flocks in Shandong province. FAdV-4 was isolated from naturally infected ducks and determined by polymerase chain reaction (PCR) amplification and DNA sequence analysis. In order to investigate the effect of FAdV-4 infection on muscovy ducks, we determined and characterized the FAdV-4 Isolate, and assessed its pathogenicity. In this study, HHS was respectively reproduced in 5-week-old muscovy duck by intramuscular injection and intranasal inoculation of allantoic fluid containing FAdV-4, ducks in the negative control group were inoculated with allantoic fluids of healthy duck embryos in the same manner. Clinical symptoms, gross and microscopic lesions, cytokines and antibodies, blood biochemical indices were detected and recorded for 12 days after infection. Typical hydropericardium and hepatitis was observed in experimental muscovy duck in the 3rd day post-inoculation (dpi). FAdV-4 can be replicated in tissues and cause pathological damage, especially in the liver and immune organs. Most of the immune-related cytokines and antibodies levels are up-regulated and then decreased, which may be caused by the initial infection and the normal immune response, later the virus caused the immunosuppression and led to the decrease of levels. To the best of our knowledge, this is the first systematic trial of the pathogenicity of FAdV-4 in muscovy ducks mainly based on the serological test, which will provide new insights into the study of the disease.

Genetic Basis of Salmonella Enteritidis Pathogenesis in Chickens

Salmonella Enteritidis (SE) is the predominant cause of the food-borne salmonellosis in humans, in part because this serotype has the unique ability to contaminate chicken eggs without causing discernible illness in the infected birds. Attempts to develop effective vaccines and eradicate SE from chickens are undermined by significant limitations in our current understanding of the genetic basis of pathogenesis of SE in this reservoir host. In this chapter, we summarize the infection kinetics and provide an overview of the current understanding of genetic factors underlying SE infection in the chicken host. We also discuss the important knowledge gaps that, if addressed, will improve our understanding of the complex biology of SE in young chickens and in egg laying hens.

Tissue colonization and circulating T lymphocytes in laying hens upon oral challenge with Salmonella enterica serovars

Evaluating the potential of Salmonella serovars for tissue colonization and egg contamination in laying hens is critical due to widespread consumption of poultry and egg-containing products. The 2009 FDA Egg Rule was implemented to target the eradication of Salmonella enterica Enteritidis (SE) from layers; however, other Salmonella serovars, such as Heidelberg (SH) and Typhimurium (ST), have also been associated with poultry-related outbreaks. We conducted this study to see if serovars other than SE could colonize in laying hens, cause egg contamination, and modulate circulating T-cell populations. Laying hens were orally gavaged with 10⁷ colony forming units (CFU) of SE, SH, or ST and assessed for colonization in spleen, ovaries, and oviduct 10 d postchallenge. Splenic colonization was similar for all the serovars; however, colonization of ovaries and oviducts was significantly higher with SH compared to SE and ST. Furthermore, SH challenge resulted in egg contamination, while SE and ST did not result in contaminated eggs. Phenotypic evaluation of peripheral blood lymphocytes showed significant reduction in CD4 cells in SH-challenged birds and lower CD8α and CD8β cells in SE-challenged birds compared to controls. Our data showed that non-SE serovars have equal or higher potential to colonize reproductive tissues of laying hens and may be accompanied by altered lymphocyte populations.

Diet supplementation with a specific melon concentrate improves oviduct antioxidant defenses and egg characteristics in laying hens

The objectives of this study were to investigate the effects of a specific melon concentrate on oviduct antioxidant defenses and egg characteristics of laying hens.Lohmann Brown hens were assigned to 2 treatment groups (n = 16 in each). One group was supplemented with the melon concentrate (26 mg/kg of feed) during 6 wk. The other group was composed of untreated hens, which served as control. Eggs were collected, weighed (yolk, albumen, shell), and analyzed (Haugh unit and albumen pH relevant for egg freshness) at the end of the supplementation period. Antioxidant status was evaluated in the oviduct measuring antioxidant enzymes by western blotting.This study demonstrated that the melon concentrate could ameliorate egg weight, and particularly yolk contribution to egg weight and egg shell weight. An increase in endogenous antioxidant defenses in the oviduct after this melon concentrate supplementation could explain the better egg characteristics. The improvement of egg quality, due to melon concentrate, may have important economic implications for future breeding programs, particularly if these effects generalize from hens to other poultry species, or even other livestock animal species.

Influence of dietary taurine and housing density on oviduct function in laying hens

Experiments were conducted to study the effects of dietary taurine and housing density on oviduct function in laying hens. Green-shell laying hens were randomly assigned to a free range group and two caged groups, one with low-density and the other with high-density housing. Each group was further divided into control (C) and taurine treatment (T) groups. All hens were fed the same basic diet except that the T groups' diet was supplemented with 0.1% taurine. The experiment lasted 15 d. Survival rates, laying rates, daily feed consumption, and daily weight gain were recorded. Histological changes, inflammatory mediator levels, and oxidation and anti-oxidation levels were determined. The results show that dietary taurine supplementation and reduced housing density significantly attenuated pathophysiological changes in the oviduct. Nuclear factor-κB (NF-κB) DNA binding activity increased significantly in the high-density housing group compared with the two other housing groups and was reduced by taurine supplementation. Tumor necrosis factor-α (TNF-α) mRNA expression in the high-density and low-density C and T groups increased significantly. In the free range and low-density groups, dietary taurine significantly reduced the expression of TNF-α mRNA. Supplementation with taurine decreased interferon-γ (IFN-γ) mRNA expression significantly in the low-density groups. Interleukin 4 (IL-4) mRNA expression was significantly higher in caged hens. IL-10 mRNA expression was higher in the high-density C group than in the free range and low-density C groups. Supplementation with taurine decreased IL-10 mRNA expression significantly in the high-density group and increased superoxide dismutase (SOD) activity in the free range hens. We conclude that taurine has important protective effects against oviduct damage. Reducing housing density also results in less oxidative stress, less inflammatory cell infiltration, and lower levels of inflammatory mediators in the oviduct. Therefore, both dietary taurine and reduced housing density can ameliorate oviduct injury, enhance oviduct health, and promote egg production in laying hens.