Protoporphyrin quantification from eggshells of laying hens challenged with infectious bronchitis virus strains (N1/88 and T strains)

Eggshells were collected at days 1, 3 and 5 post infection from unvaccinated Isa Brown laying hens challenged with infectious bronchitis virus (IBV) strains N1/88 or T as well as from a control group of unvaccinated hens. Shell reflectivity (%) and shell color L* were measured on shells with and without cuticle and were further processed for the quantification of protoporphyrin IX (PP IX) from the same shell with and without the presence of cuticle. Shell reflectivity and shell color L* values for the control eggs were significantly lower (P < 0.0001) compared to those from hens challenged with both strains of IBV and were also significantly lower on day 1 compared to days 3 and 5 p.i. The PP IX was quantified by spectrophotometric analysis of digested eggshell solutions. The mean PP IX in 1g of shell with and without cuticle was significantly higher on day 1 compared with days 3 and 5. The amount of PP IX in the shell decreased with time post infection for the IBV groups. The amount of PP IX in whole egg shell was highest for the control group and lowest for the T strain group, with the N1/88 group intermediate.