The downside of broiler vaccination

Molecular and metabolic responses to immune stress in the jejunum of broiler chickens: transcriptomic and metabolomic analysis

In the large poultry industry, where farmed chickens are fed at high density, the prevalence of pathogens and repeated vaccinations induce immune stress, which can significantly decrease the production performance and increase the mortality. This study was designed to shed light on the molecular mechanisms and metabolic pathways involved in immune stress through an in-depth analysis of transcriptomic and metabolomic changes in jejunum samples from the broilers. Two groups were established for the experiment: a control group and an LPS group. LPS group received an intraperitoneal injection of LPS solution at a dose of 250 μg per kg at 12, 14, 33, and 35 d of age, whereas the control group received a sterile saline injection. The severity of immune stress was assessed using the Disease Activity Index. A jejunal section was collected to measure the intestinal villus structure (villus length and crypt depth). RNA sequencing and metabolomics data analysis were conducted to reveal differentially expressed genes and metabolites. The results showed that the DAI index was increased and jejunal villus height/crypt depth was decreased in the LPS group. A total of 96 differentially expressed genes and 672 differentially accumulating metabolites were detected in the jejunum by LPS group compared to the control group. The comprehensive analysis of metabolomic and transcriptomic data showed that 23 pathways were enriched in the jejunum and that appetite, nutrient absorption, energy and substance metabolism disorders and ferroptosis play an important role in immune stress in broilers. Our findings provide a deeper understanding of the molecular and metabolic responses in broilers to LPS-induced immune stress, suggesting potential targets for therapeutic strategies to improve the production performance of broiler chickens.

A Comprehensive Review on Bacterial Vaccines Combating Antimicrobial Resistance in Poultry

Bacterial vaccines have become a crucial tool in combating antimicrobial resistance (AMR) in poultry. The overuse and misuse of antibiotics in poultry farming have led to the development of AMR, which is a growing public health concern. Bacterial vaccines are alternative methods for controlling bacterial diseases in poultry, reducing the need for antibiotics and improving animal welfare. These vaccines come in different forms including live attenuated, killed, and recombinant vaccines, and they work by stimulating the immune system to produce a specific response to the target bacteria. There are many advantages to using bacterial vaccines in poultry, including reduced use of antibiotics, improved animal welfare, and increased profitability. However, there are also limitations such as vaccine efficacy and availability. The use of bacterial vaccines in poultry is regulated by various governmental bodies and there are economic considerations to be taken into account, including costs and return on investment. The future prospects for bacterial vaccines in poultry are promising, with advancements in genetic engineering and vaccine formulation, and they have the potential to improve the sustainability of the poultry industry. In conclusion, bacterial vaccines are essential in combating AMR in poultry and represent a crucial step towards a more sustainable and responsible approach to poultry farming.

Effects of access to feed, water, and a competitive exclusion product in the hatcher on some immune traits and gut development in broiler chickens

This study evaluated the effect of access to feed, water, and the competitive exclusion (CE) product Broilact®, administered in the hatcher, on broiler performance, caecal microbiota development, organ development, intestinal morphology, serum levels of IgY and vaccine-induced antibody responses.In total, 250 chicks were hatched in a HatchCare^TM hatcher and divided into four groups, given access to feed, water and the CE product sprayed on the chicks (CEs); access to feed, water, and the CE product in water (CEw); access to feed and water (Cpos); or no access to feed and water (Cneg) in the hatcher. At the research facility, 10 chicks per hatching treatment were euthanized for organ measurements. The remaining 200 chicks were randomly distributed to 20 pens. On d 11, all birds were vaccinated against avian pneumovirus (APV). Three focal birds per pen were blood-sampled weekly for quantification of IgY and serum antibodies to APV. On d 11 and 32, two birds per replicate pen were euthanised for organ measurements and sample collection. Feed intake and body weight were recorded weekly.Delayed access to feed and water reduced weight gain and feed intake early in life. At the end of the study, no differences in body weight remained.There were some early effects on organs, with depressed intestinal development and higher relative gizzard weight for the Cneg group at placement. No treatment effects on the immune traits measured were detected. The relative abundance of seven bacterial genera differed between treatment groups at d 11 of age. The results suggested that chickens are capable of compensating for 40 h feed and water deprival post-hatch. Provision of Broilact® did not have any persistent performance-enhancing properties, although different outcomes under rearing conditions closer to commercial production cannot be ruled out.

Factor Influences for Diagnosis and Vaccination of Avian Infectious Bronchitis Virus (Gammacoronavirus) in Chickens

Infectious bronchitis virus (IBV) is a major economic problem in commercial chicken farms with acute multiple-system infection, especially in respiratory and urogenital systems. A live-attenuated and killed vaccine is currently immunized to control IBV infection; however, repeated outbreaks occur in both unvaccinated and vaccinated birds due to the choice of inadequate vaccine candidates and continuous emergence of novel infectious bronchitis (IB) variants and failure of vaccination. However, similar clinical signs were shown in different respiratory diseases that are essential to improving the diagnostic assay to detect IBV infections. Various risk factors involved in the failure of IB vaccination, such as various routes of application of vaccination, the interval between vaccinations, and challenge with various possible immunosuppression of birds are reviewed. The review article also highlights and updates factors affecting the diagnosis of IBV disease in the poultry industry with differential diagnosis to find the nature of infections compared with non-IBV diseases. Therefore, it is essential to monitor the common reasons for failed IBV vaccinations with preventive action, and proper diagnostic facilities for identifying the infective stage, leading to earlier control and reduced economic losses from IBV disease.

Histopathologic Lesion Scoring and Histomorphometric Methods for Measuring Vaccine Reactions in the Trachea of Broiler Chickens

Severity of the tracheal histologic inflammatory response induced in broilers by ocular inoculation of two infectious bronchitis (IBV) and three Newcastle disease virus (NDV) commercial vaccines were evaluated. The vaccine was delivered by eye drop with a coarse spray to day-old chicks. The vaccines were given individually or in various combinations and were evaluated relative to nonvaccinated controls. Evaluations were performed on postvaccination (PV) days 7 and 14. Histologic endpoints included semiquantitative severity scoring of inflammatory components and quantitative morphometric determinations of inflammatory cell concentration, mucosal thickness, and percentage of ciliated mucosal surface. Strong positive correlations were observed between routine severity scoring and morphometric inflammatory parameters, whereas a negative correlation was present between inflammation severity and the percentage of mucosal ciliation. Variable, sometimes extensive, and often statistically significant differences in inflammatory responses were observed between the various vaccines. One IBV Massachusetts strain vaccine (IBV-A) produced the greatest overall inflammatory response when given alone or in combination with the NDV vaccines. Enhancement of tracheitis was seen on PV day 14 by covaccination of IBV-A with the NDV vaccines, but not by covaccination of another IBV Massachusetts strain vaccine (IBV-B) with NDV. Reduction in cilia percentage was observed for all vaccine groups relative to controls on PV day 7. However, although reactive cilia regeneration occurred on PV day 14 for most vaccine groups, a cilia regenerative response was not apparent for individual or NDV combination vaccination for IBV-A. The study also demonstrates that substantial microscopic trachea pathology may be present in vaccinated birds not exhibiting apparent clinical respiratory signs.