Influence of different rearing systems on natural immune parameters in broiler turkeys

Effect of silvopasture system on fearfulness and leg health in fast-growing broiler chickens

A silvopasture system intentionally integrates trees, forages, and livestock, allowing dual land use. These systems can provide high-quality habitat for broiler chickens; however, such systems have not been widely adopted by the broiler industry in the United States. The objective of this study was to examine the effect of silvopasture versus open pasture access on fearfulness and leg health in fast-growing broiler chickens. A total of 886 mixed-sex Ross 708 chicks in Experiment 1 (Exp 1) and 648 chicks in Experiment 2 (Exp 2) were housed in coops and had access to 16 (Exp 1) or 12 (Exp 2) 125m2 silvopasture plots (x̄ = 32% canopy cover) or open pasture plots (no canopy cover) from day 24 of age. Fearfulness was measured using a tonic immobility test (tonic immobility duration), and leg health was assessed by quantifying footpad dermatitis, hock burns, gait, and performing a latency-to-lie test on days 37-39 of age. Birds in the silvopasture treatment were less fearful than birds in the open pasture treatment. Overall, birds in both silvopasture and open pasture systems had excellent leg health. Silvopasture birds had lower footpad dermatitis scores than open pasture birds. Silvopasture birds tended to have worse gait than open pasture birds in Exp 1, but not in Exp 2. Hock burn scores and latency-to-lie did not differ between treatments in Exp 1 or Exp 2. Raising birds in silvopasture reduced fear and improved footpad health compared to birds raised in open pastures, which indicates that silvopasture systems provide some benefits for affective state and leg health in fast-growing broilers.

Short-term and long-term effects of antimicrobial use on antimicrobial resistance in broiler and turkey farms

ABSTRACTAntimicrobials have been widely used in poultry, promoting antimicrobial resistance (AMR) emergence and spread. Resistant bacteria selected by antimicrobial use (AMU) can contaminate the farm environment and transfer resistance genes to other bacteria, providing opportunities for persistence and (re-)colonization of subsequent flocks and potentially jeopardizing antimicrobial treatments. We investigated the effects of AMU on AMR in poultry in the long-term (due to historical AMU in the farm) and in the short-term (due to current AMU in a flock). Litter samples from 35 broiler and 35 turkey farms in North-East Italy were sampled longitudinally for AMR testing of E. coli indicator bacteria in 2019/2020. Differences in AMR as a function of historical AMU (Defined Daily Doses in 2016-2018), current AMU in the sampled flock, farm size and season were tested using Generalized Estimating Equation regression analysis. In both broilers and turkeys, the highest resistance levels were observed for sulfamethoxazole (>70%), followed by ampicillin (54-60%). Only few positive associations between historical levels of penicillin use and the specific resistance levels to penicillin in broiler farms, and the overall historical AMU and resistance to trimethoprim in turkey flocks, were significant. Current AMU showed significant effects on resistance to sulfamethoxazole, trimethoprim, ciprofloxacin and tetracycline in turkey flocks. Significant effects of farm size on some AMR levels were also identified. We found a stronger association between current AMU and AMR compared to historical AMU and AMR. AMR persistence in the farm environment in absence of direct AMU pressure needs to be further investigated.

The Benefit of Hedgerow Access on the Health and Growth Rate of Pasture Raised Broiler Chickens

Pasture rearing is an increasingly common option for small farms to produce humanely raised poultry products for an expanding market, however profit margins tend to be much lower for pastured poultry producers than for those that opt for conventional indoor rearing. Research into simple methods to optimize the growth and health of pasture-raised poultry can help small farmers maximize meat yields and decrease the morbidity and mortality of their flock, ultimately leading to higher profit margins and improved animal welfare. The objective of this study was to measure how the inclusion of mature, native foliage into pastures can impact the production performance and overall health status of two different popular breeds of commercial broiler chickens; fast-growing Cornish cross and slower growing Red rangers. During the finisher phase (30–78 days old), pastured chickens were separated by breed into either a treatment population with access to a mature bordering hedgerow, or a control population without access to a hedgerow. Weekly weight gain, daily feed intake and basic hematologic values were used to evaluate differences in the production performance and health status between each population. We found that hedge access led to a significant improvement in the rate of gain of the Cornish cross without an associated increase in feed intake, suggesting that the addition of hedges can increase meat yields in fast-growing broilers without increasing feed costs. Red rangers with hedge access demonstrated an improved ability to neutralize bacterial pathogens in whole blood and a lesser degree of hemodilution compared to control populations, suggesting improved immune function and a lower degree of heat stress in these populations. We conclude that the addition of natural environmental enrichment such as mature foliage to grass pastures can lead to improved production performance in fast-growing broilers and improvements in the health and immune function of slower growing broiler chickens.

An OMV-Based Nanovaccine Confers Safety and Protection against Pathogenic Escherichia coli via Both Humoral and Predominantly Th1 Immune Responses in Poultry

Avian pathogenic Escherichia coli (APEC) infection in poultry causes enormous economic losses and public health risks. Bacterial outer membrane vesicles (OMVs) and nano-sized proteolipids enriched with various immunogenic molecules have gained extensive interest as novel nanovaccines against bacterial infections. In this study, after the preparation of APEC O2-derived OMVs (APEC_OMVs) using the ultracentrifugation method and characterization of them using electron microscopy and nanoparticle tracking analyses, we examined the safety and vaccination effect of APEC_OMVs in broiler chicks and investigated the underlying immunological mechanism of protection. The results showed that APEC_OMVs had membrane-enclosed structures with an average diameter of 89 nm. Vaccination with 50 μg of APEC_OMVs had no side effects and efficiently protected chicks against homologous infection. APEC_OMVs could be effectively taken up by chicken macrophages and activated innate immune responses in macrophages in vitro. APEC_OMV vaccination significantly improved activities of serum non-specific immune factors, enhanced the specific antibody response and promoted the proliferation of splenic and peripheral blood lymphocytes in response to mitogen. Furthermore, APEC_OMVs also elicited a predominantly IFN-γ-mediated Th1 response in splenic lymphocytes. Our data revealed the involvement of both non-specific immune responses and specific antibody and cytokine responses in the APEC_OMV-mediated protection, providing broader knowledge for the development of multivalent APEC_OMV-based nanovaccine with high safety and efficacy in the future.

Natural immunity in conventionally and organically reared turkeys and its relation with antimicrobial resistance

Suboptimal animal welfare may affect natural immunity, rendering animals more susceptible to environmentally conditioned diseases, including those requiring antimicrobial treatment, which may promote antimicrobial resistance (AMR) in bacterial populations. Herewith, we tested the hypothesis that conventionally raised turkeys have higher levels of AMR in indicator Escherichia coli bacteria, but lower levels of natural immunity, as compared to turkeys reared under organic conditions. Litter and serum samples were collected from 28 conventional and 4 organic turkey farms: E. coli isolates from litter were tested for resistance to 14 antimicrobials, while 3 parameters of natural immunity (i.e., lysozyme, hemolytic complement levels, and serum bactericidal activity) were assessed in the sera. Resistant E. coli isolates were identified in both conventional and organic farms but generally more frequently in conventional farms. High rates of resistance to ampicillin (96%), tetracycline (95%), streptomycin (82%), sulfamethoxazole (80%), ciprofloxacin (73%), and trimethoprim (71%), as well as high rates of multiresistance, were observed in conventional farms. Organically raised turkeys had significantly higher levels of lysozyme and serum bactericidal activity than conventional turkeys, and these levels were also higher in turkeys housed in farms where AMR frequency was lower. Findings support the hypothesis that conventional farming conditions may affect turkeys' natural immunity, rendering the animals more susceptible to environmentally conditioned diseases requiring antimicrobial treatment, which would in turn promote AMR. Reducing AMR in turkey farming is therefore more likely to be successful when considering animal welfare as an option to reduce the need of antimicrobial use.