Abstract
Nematode infections may induce immune-modulatory effects and influence host-immune responses to other pathogens. The aim of the study was to investigate whether a mixed nematode-infection influences non-specific and vaccine-induced humoral immunity against Newcastle Disease Virus (NDV), Infectious Bronchitis Virus (IBV), and Avian Metapneumovirus (AMPV) in already vaccinated hens of a dual-purpose (Lohmann Dual, LD) or a layer genotype (Lohmann Brown Plus; LB). Until 17 weeks-of-age, LD (n = 70) and LB (n = 109) hens were vaccinated against major bacterial and viral diseases and coccidiosis. At 24 weeks-of-age, the hens received either a placebo or an oral inoculation of 1,000 infectious eggs of A. galli and H. gallinarum. Plasma total immunoglobulin (Ig) isotypes (IgY, IgM, IgA) levels and vaccine-induced antibody titers against NDV, IBV, and AMPV were determined from 2 to 18 weeks post-infection (wpi). Infections had no suppressing effect on total Ig isotypes IgY, IgM, and IgA as well as on vaccine-induced antibody titers against NDV, IBV, and AMPV (P > 0.05). Overall, LB hens had higher levels of IgY, IgM, and IgA than those of LD hens (P < 0.05). There were no differences between IBV titers of the two genotypes (P > 0.05). Independent of infection status of the hens, NDV titers were higher in LB hens than in LD hens at wpi 2 (P < 0.05), but not in following weeks (P > 0.05). Uninfected LD hens had lower AMPV titers than their infected counterparts at 6 and 14 wpi (P < 0.05). Regardless of nematode infection, LD hens revealed a higher risk of responding weak to vaccination against NDV (odds ratio = 5.45; P = 0.021) and AMPV (odds ratio = 13.99, P < 0.001) than did LB hens (P > 0.05). We conclude that nematode infections have no adverse effects on non-specific and vaccine-induced humoral immunity in either genotype. LB hens have higher levels of total immunoglobulin isotypes than LD hens. Except for IBV, vaccine-induced humoral immune responses show a dependency on genotype. Dual-purpose hens show lower responsiveness to vaccinations against NDV and AMPV, possibly due to factors associated with increased body fat reserves in this genotype.
Highlights
Modern chicken genotypes that are used for commercial egg or meat production have been genetically selected for oneway production mode only, i.e., egg or meat production
There was no significant difference between Lohmann Brown Plus (LB) and Lohmann Dual (LD) hens in terms of number of eggs per gram feces (EPG) at any time point (P > 0.05)
The overall average A. galli and H. gallinarum counts, which were based on the sum of the all juvenile and mature stages of the worms, did not significantly differ between the two genotypes (P > 0.05), whereas LB hens had higher levels of reinfection with H. gallinarum than did LD hens (P < 0.05)
Summary
Modern chicken genotypes that are used for commercial egg or meat production have been genetically selected for oneway production mode only, i.e., egg or meat production This is mainly because of the strong genetic antagonism between reproduction and growth traits in chickens [1]. Because egg production is a sex-dependent phenotype for which layer genotypes are strongly selected for, poor growth performance and efficiency of male birds of the layer lines are not competitive to that of meat-type chickens. One of the available potential alternatives to culling of male birds is the reintegration of the so-called dual-purpose genotypes in production systems in order to use female birds for egg production, while counterpart males are used for meat production [1, 6]. Whether dual-purpose genotypes have improved health and welfare associated traits remain largely unknown
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