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.

The shelf-life of eggs is determined by various government and industry agencies, as well as by retailers. It is based on the internal quality of the eggs and their microbiological safety. The avian egg possesses many intrinsic anti-microbial properties that are designed to ensure the safety of the developing chick. However, these same properties also protect the consumer of the egg. Many factors influence the internal quality and the microbiological safety of eggs, and this chapter takes a look at these factors. This chapter discusses technologies for increasing the shelf-life of eggs. Of primary importance is the handling and storage of eggs. This chapter also discusses the issue of coatings to increase shelf-life.

Semi-intensive free-range farm systems are common in Australia, and these systems frequently practise on-range feeding. The objective of this study was to investigate the benefit of on-range choice feeding on flock performance, egg quality, and range use of free-range laying hens using black soldier fly larvae (Hermetia illucens, BSF). A total of 160 mature ISA brown laying hens, previously determined to range daily, were allocated to a control group (control) or a treatment group (BSF) with various replicates depending on the parameter investigated. All hens were fed ad libitum indoors with a wheat-soy based diet formulated according to breed requirements. Black soldier fly hens were offered dried BSF larvae ad libitum on the range. Body weight, feed intake, BSF intake, egg production, feed conversion ratio, internal and external egg quality parameters, and individual range use using radio-frequency identification (RFID) technology was evaluated. Black soldier fly hens consumed on average 15 ± 1.7 g BSF larvae/hen per day. There were no differences between BSF and control hens for any of the performance parameters obtained (P > 0.05). Egg weight, shell weight, and shell thickness of eggs from BSF hens were significantly lower (P = 0.003, P = 0.001, and P = 0.004, respectively) than those of eggs from control hens. Egg yolk colour was significantly paler in eggs from BSF hens (P < 0.001). No significant ranging differences between the BSF and control hens were observed (P > 0.05) except for BSF hens showing longer total maximum time for a single visit to the range (P = 0.011). In conclusion, the average intake of BSF larvae indicated a good level of acceptance. Feed formulation should be adjusted for the intake of the choice fed source. The impact of choice-feeding on range use was minor.

The hypothesis of this research was that livestock movement is related to feed availability and therefore spatial and temporal livestock information. Collected through autonomous position tracking devices, this may be used as an indicator of available feed. Two separate experiments were undertaken in which grazing cattle were tracked with store-on-board GPS. Additionally, pasture biomass was monitored with active optical sensing and manual cuts throughout the duration of the experiments. Cattle grazing behaviour was determined from the GPS data with speed-based behaviour models. The time cattle spent grazing per day altered with changing pasture biomass in both experiments. The daily time spent grazing was commonly found to initially be almost constant before following a quadratic trend, increasing before decreasing as available biomass declined. Development of behaviour models for autonomous livestock monitoring could assist producers with decisions related to rotation and feed management.

Nine experiments were performed to investigate how the synthesis and/or deposition of protoporphyrin IX (PP IX) into eggshell is influenced in brown-egg laying hens. The findings obtained in the first experiment (Chapter 2) showed that flock age and production system affected overall eggshell and egg quality. Egg weight was significantly higher in cage eggs, while albumen height was significantly higher in barn eggs. The mammillary layer ultrastructural variables showed no clear relationship with production system and flock age. Cuticle cover (ΔE*ab) was significantly higher in barn eggs compared with free range and cage eggs and was significantly higher in eggs from the 44 week old flock than for 64 and 73 week old flocks. In 1 gram of eggshell with and without cuticle, there was more PP IX in cage eggs followed by free range and barn eggs. The findings in experiment 2 (Chapter 3) indicate that eggs laid earlier in the day had deeper brown eggshell colour compared with the eggs laid later in the day. Egg position in a clutch had a clearer effect on eggshell quality in long clutches, as compared with medium and short clutches. The findings of the third experiment (Chapter 4) showed that different infectious bronchitis virus (IBV) strains affected the level of PP IX in eggshell differently. In unvaccinated laying hens, the mean PP IX per gram of shell was significantly higher on day 1 post-infection (p.i.) compared to day 7, after which PP IX increased with day p.i. In unvaccinated and vaccinated laying hens, PP IX decreased with increased day p.i. until day 12. The effect on loss of shell colour was more marked in the T strain infected group followed by N1/88, Vic S and A3 strains. Experiment four (Chapter 5) investigated reference gene stability in the shell gland in relation to time-points (time post-oviposition) of eggshell formation and nicarbazin treatment. The two most stable reference genes selected, HPRT1 and HMBS, were used for the normalisation of gene expression data obtained in experiment five (Chapter 6). The findings in experiment five showed that mitochondria per cell did not vary significantly with different time-points of eggshell formation and nicarbazin treatment. Genes involved in the synthesis of PP IX were regulated differentially in relation to time-points of eggshell formation. Feeding nicarbazin caused down-regulation of the ALAS1 gene that resulted in lower production of PP IX appearing in the shell gland tissue and eggshell. Experiment six (Chapter 7) investigated reference gene stability in the shell gland and spleen of infectious bronchitis virus (IBV) infected hens. The two most stable reference genes selected, TBP and YWHAZ, were used for the normalisation of gene expression data obtained in experiments seven and eight (Chapters 8 and 9). The RNA-sequencing findings in experiment seven showed that there were no differentially expressed genes (DEGs) involved in the mucosal immune system and eggshell formation in the shell gland between IBV challenged and control laying hens. However, there were 1608 and 1806 DEGs at 5 and 15 hrs time-points of eggshell formation, respectively. The Gene Ontology (GO) terms and functional gene analysis showed that the DEGs at 5 hr post-oviposition were mainly involved in ion transport and synthetic activities, while the DEGs at 15 hr were involved in energy metabolism and secretory activities, reflecting the peak stage of eggshell formation. The findings in experiment eight (Chapter 9) showed that IBV T infection significantly lowered mitochondrial count per cell in the shell gland region of the oviduct but not in the magnum or isthmus. The expression levels of nuclear DNA encoded genes involved in mitochondrial biogenesis and fission showed no clear correlation with mitochondrial count and were not significantly different between the control and challenged samples. The expression levels of all the genes except for PGC-1α were significantly affected by the time-points of eggshell formation. Experiment nine (Chapter 10) attempted to localize ALAS1, ALAD and FECH enzymes in shell gland tissue collected at different time-points (time post-oviposition) and in response to nicarbazin treatment. The findings showed that these antibodies did not recognise their respective proteins, possibly due to their amino acid sequences being derived from humans. PP IX fluorescence was not detected in Zenker Formol fixed tissue sections, stained or unstained, taken at different time-points and with or without nicarbazin treatment. Future work is suggested using chicken specific antibodies to localise cells involved in PP IX synthesis. Taken together, the findings in the current study broaden the understanding of factors affecting the synthesis and deposition of PP IX into eggshells.

The quality of the egg encompasses its chemical composition, nutritional quality as a human food source, sensory qualities including appearance and special nutraceutical benefits for human health. Eggs contain all essential nutrients for human health except for dietary fibre and vitamin C. This volume also discusses handling, packaging and storage of eggs, conditions that affect the quality of the product that reaches the consumer. The microbiological safety of eggs is of paramount importance as eggs have been implicated in outbreaks of food-borne illness, mainly caused by Salmonella. Fortunately, by virtue of its role in nature, the egg possesses many anti-microbial properties, and these properties can be maintained and enhanced for the benefit of consumers. This volume, Achieving sustainable production of eggs Volume 1: Safety and quality, explores the wealth of research addressing these themes.

Avian infectious bronchitis (IB) is common in all parts of the world and is acute and highly infectious (Jackwood and de Wit, 2013). The infectious bronchitis virus (IBV) belongs to the family Coronaviridae, which consists of RNA-enveloped pleomorphic viruses that possess club-shaped surface projections that give the appearance of a "corona" or fringe (Almeida et al., 1968). The complete virus contains four polypeptides: the membrane protein, the envelope protein, the nucleocapsid protein, and large spike glycoprotein (S) (McMartin, 1993). The S protein is cleaved posttranslationally into S1 and S2 subunits (Jackwood et al., 2001). The section of the S gene that codes for the S1 subunit protein is the site of the majority of the variation between strains (Cavanagh et al., 1992; Adzhar et al., 1996). Only small changes in amino acid sequences are needed to produce a different serotype, which results in a high-evolution rate for IBV. The numerous antigenically diverse strains, almost as many serotypes, and the rapid evolution of yet more variant strains complicate the understanding of this disease (Ignjatovic et al., 2002).

Free-range laying hen systems are increasing in number within Australia. Variation in outdoor stocking densities has led to development of a national information standard on free-range egg labeling, including setting a maximum density of 10,000 hens per hectare. However, there are few data on the impacts of differing outdoor densities on production and egg quality. ISA Brown hens in small (150 hens) flocks were housed in identical indoor pens, each with access (from 21 weeks) to different sized ranges simulating one of three outdoor stocking densities (2 replicates each: 2,000 hens/hectare (ha), 10,000 hens/ha, 20,000 hens/ha). Hen-day production was tracked from 21 through 35 weeks with eggs visually graded daily for external deformities. All eggs laid on one day were weighed each week. Eggs were collected from each pen at 25, 30, and 36 weeks and analyzed for egg quality. There were no effects of outdoor stocking density on average hen-day percentage production (P = 0.67), egg weight (P = 0.09), percentages of deformed eggs (P = 0.30), shell reflectivity (P = 0.74), shell breaking strength (P = 0.07), shell deformation (P = 0.83), or shell thickness (P = 0.24). Eggs from hens in the highest density had the highest percentage shell weight (P = 0.004) and eggs from the lowest density had the highest yolk color score (P < 0.001). The amount of cuticle present did not differ between densities (P = 0.95) but some aspects of shell colors (P ≤ 0.01) and location of protoporphyrin IX (P = 0.046) varied. Hen age affected the majority of measurements. Stocking density differences may be related to hen diet as previous radio-frequency identification tracking of individual hens in these flocks showed birds used the range for longer in the lowest density and the least in the highest density, including depleting the range of vegetation sooner in the smaller ranges. An additional study assessing the relationship between individual hen range use, nutrition, and egg quality is warranted.

The welfare of laying hens is dependent on the provision of appropriate housing, excellent management, high-quality feed, and prevention and appropriate treatment of diseases. This volume, 'Achieving sustainable production of eggs Volume 2: Animal welfare and sustainability', provides a detailed account of laying hens' nutritional requirements and a practical guide to maintaining their health. The welfare of hens is addressed by examining their welfare standards, identifying and discussing welfare issues affecting free-range laying hens, reviewing the welfare costs and benefits of beak trimming, and investigating the management of laying hen flocks with intact beaks. The sustainability of the egg industry is addressed from two perspectives: waste management in egg production and an assessment of the sustainability of organic egg production.

Eggs were collected from commercial caged layer flocks in early, mid, late and very late lay. Eggs were candled and scored for translucency. Cuticle cover was estimated using MST cuticle stain and a Konica Minolta hand-held spectrophotometer. Traditional measures of egg quality were determined using specialised equipment (TSS, U.K.) Shell ultrastructural features were scored following plasma ashing of shell samples and viewing under a benchtop scanning electron microscope. Translucency tended to be higher in late lay flocks and shell quality was lower. Cuticle cover was relatively uniform for young flocks but much more variable in older flocks. The incidence of unfavourable shell ultrastructural features was higher for older flocks. This study is on-going so, as the sample size increases, new insights will be obtained.