Egg shell quality and egg internal quality are of major importance to the egg industry worldwide and may be measured in a range of ways both commercially and in research facilities. Egg quality is influenced by a range of factors including strain of bird, age of bird, nutrition, moult status, water quality, general stress, heat stress, disease, housing, production system, environmental contaminants and use of proprietary products designed to improve egg quality. Improved understanding of the way in which the egg and egg shell are formed, including knowledge of the proteins comprising the organic matrix of the shell has assisted with diagnosis of the causes of egg shell quality problems and with genetic selection for good quality. Ongoing technological advances have led to improved in-line monitoring of egg shell quality. Egg quality is also important for food safety as eggs are periodically implicated in cases of food-borne illness.

Understanding of host pathogen interactions is important in planning strategies for effective control of the pathogen. The present study investigated the regulation of genes involved in the activation of splenic immune system in mature laying chickens challenged with T strain of infectious bronchitis virus (IBV). Among all the genes studied, the relative expression levels of Fas cell surface death receptor (FAS), interleukin 7 (IL7), IL18, proteasome subunit alpha 3 (PSMA3), major histocompatibility complex, class II (MHCII), interferon alpha (IFNα), immunoglobulin A (IgA), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) were significantly (p < 0.05) upregulated, while Toll-like receptor 7 (TLR7) and TLR5 were significantly downregulated in the challenge compared with the control group. Genes such as vascular cell adhesion molecule 1 (VCAM1), FK506-binding protein 1B (FKBP1B), transforming growth factor-beta 3 (TGFB3), NLR family pyrin domain containing 3 (NLRP3), TYRO3 protein tyrosine kinase (TYRO3), TNF receptor-associated factor 3 (TRAF3), C-X-C motif chemokine receptor 4 (CXCR4), macrophage inflammatory protein-3 (MIP3A), TLR2-1, TLR3, and TLR21 were not altered in mRNA expression levels between the challenge and control groups. In conclusion, the splenic immune response to IBV infection involved the regulation of cytokines, TLRs and NF-κB.

Ten reference genes were investigated for normalization of gene expression data in the shell gland of laying hens. Analyses performed with geNorm revealed that hypoxanthine phosphoribosyltransferase 1 (HPRT1) and hydroxymethylbilane synthase (HMBS) were the two most stable reference genes in response to post-oviposition time alone (POT) or with nicarbazin treatment (POT+N) of laying hens. NormFinder analyses showed that the two most stable reference genes in response to POT and POT+N were 18S ribosomal RNA (18S rRNA), ribosomal protein L4 (RPL4) and HMBS, RPL4, respectively. BestKeeper analyses showed that 18S rRNA, RPL4 and HPRT1, HMBS were the two most stable reference genes for POT, and POT+N, respectively. Of the ten reference genes, all except B2M showed geNorm M <0.5, suggesting that they were stably expressed in the shell gland tissue. Consensus from these three programs suggested HPRT1 and HMBS could be used as the two most stable reference genes in the present study. Expression analyses of four candidate target genes with the two most and the two least stable genes showed that a combination of stable reference genes leads to more discriminable quantification of expression levels of target genes, while the least stable genes failed to do so. Therefore, HMBS and HPRT1 are recommended as the two most stable reference genes for the normalization of gene expression data at different stages of eggshell formation in brown-egg laying hens. Available statistical programs for reference gene ranking should include more robust analysis capability to analyse the gene expression data generated from factorial design experiments.

The comparative and sequential histopathology of different tissues of unvaccinated laying hens and cockerels were studied in chickens exposed to T and N1/88 strain of infectious bronchitis virus (IBV). The Harderian gland and trachea of hens and cockerels in both T- and N1/88-infected groups were damaged to a similar extent. The cecum was unaffected for both strains of IBV in both hens and cockerels. The sequential histopathological changes in hens revealed that IBV multiplies initially in the Harderian gland, then in the tracheal mucosa and simultaneously in the kidney and regions of the oviduct such as the magnum, tubular shell gland, and shell gland pouch. In cockerels, IBV multiplies first in the Harderian gland, then simultaneously in the trachea and kidney. Overall, the severity and persistence of lesions were greater in the kidneys of T-infected hens as compared with N1/88-infected hens. However, pathological changes in the kidney were mild in T- and N1/88-infected cockerels.

Eggs were collected from Hy-Line brown flocks aged 33, 50 and 67 wk. Thirty eggs from each flock were analyzed to determine the reliability of MST (MS Technologies, U.K.) cuticle blue stain as an indicator of the presence of cuticle and the effective removal of cuticle by use of an EDTA solution. Another 30 eggs, collected at the same time from each flock, were processed for the quantification of protoporphyrin IX (PP IX) from the eggshell with and without the presence of cuticle. The L*a* components of the colour space system were significantly different among the age groups. There was a high degree of correlation between the extent of MST cuticle blue staining and the amount of cuticle on the eggshell as recorded by scanning electron microscopy. PP IX pigment was quantified by spectrophotometric analysis of digested eggshell solutions.

Infectious bronchitis virus (IBV) strains primarily infect the epithelial tissues of the respiratory tract and kidneys but they also multiply in the egg forming region of the oviduct, causing paleness of shell colour in brown egg laying hens. Protoporphyrin IX (PP IX) is the main eggshell pigment in the eggs of laying hens, in addition to other pigments such as biliverdin. The brown pigment has a number of functions including specific gram positive antibacterial action and positive influence on consumer perceptions. The aim of the current study was to assess any significant effect of different IBV strains on the shell colour in brown shelled eggs. Eggs were collected from day 2 to day 22 post infection (p.i) from unvaccinated and vaccinated laying hens challenged with IBV wild strains (T and N1/88) and vaccine strains (A3 and Vic S) in addition to a control group hens. Eggshells were processed for measurement of shell reflectivity (%), spectrophotometry (SCI L* component), and protoporphyrin IX (PP IX) quantification from shells with and without cuticle. There was a significant effect (P<0.05) of day p.i and viral strain on shell reflectivity, SCI L* and PP IX in eggshells with and without cuticle. The values for shell reflectivity and SCI L* increased and those for PP IX decreased with increased day p.i until day 12, suggesting an increasing viral load in the shell gland. The shell reflectivity and L* values decreased insignificantly after day 12 and slightly increased again towards day 22. The amount of PP IX tended to increase after day 12 p.i. but this was not statistically significant, suggesting that after day 12 p.i., the viral load started declining and thus shell colour was restoring in the challenged hens. The higher shell reflectivity and SCI L* values, and lower PP IX values, of eggshells from T and N1/88 followed by Vic S strain infected birds suggests that the T strain was most severe in its effect followed by N1/88 and Vic S with A3 being the more mild one. The values of shell reflectivity, SCI L* and PP IX were not significantly different for eggshells from unvaccinated and vaccinated laying hens in the whole eggshell, but were significant in shells from which cuticle had been removed.

Microbial populations from samples of six pooled eggs were enumerated for Enterobacteriaceae on violet red bile glucose agar (Oxoid, Australia) plates with overlay (purple-red colonies). Presumptive colonies were counted and reported as log cfu/mL of egg rinsate. Translucency tended to be higher in late lay flocks. The Enterobacteriaceae count on the egg shell surface was slightly higher in late lay flocks but was not significantly different from that of the flocks in early lay. 'Salmonella' Infantis was isolated from egg shell rinse. Samples were collected throughout the year 2010-2011. This study is on-going so, as the sample size increases, new insights will be obtained.

The effect of two strains of infectious bronchitis virus (IBV-T and N1/88 strains) on internal and external quality of eggs was studied in unvaccinated Isa Brown hens in full lay. Overall, there was no decline in egg production in either of the infected groups. Long-lasting effects were observed on egg internal quality of T strain-infected hens. Effects on internal quality in the N1/88 strain-infected group were more short term. The only significant effect of IBV infection on shell quality measurements was paler egg shells from the T-infected birds for the first 5 weeks post-infection.

Free-range egg production is rapidly growing in Australia with an estimated retail value market share of 48% (AECL, 2014). Laying hens exposed to pasture range may experience reduced performance, poor enteric health and increased mortality (Ruhnke et al., 2014). In addition, egg quality can also be affected, indicated by the increased number of damaged and misplaced eggs as well as decreased egg shell quality (Kijlstra et al., 2009). These effects may be related to excessive fiber digestion and reduced nutrient uptake. The addition of multi-enzymes or organic acids to free-range layer diets may improve the digestion of nutrients, thus increasing performance, gut health and egg quality. A study was conducted to investigate the effect of range types and feed additives on performance and egg quality of ranging laying hens.