In ovo sexing of chicken eggs by fluorescence spectroscopy

Fast, accurate, and cost-effective poultry sex genotyping using real-time polymerase chain reaction

According to The Organization for Economic Co-operation and Development (OECD), demand for poultry meat and eggs consumption is growing consistently since poultry meat and eggs are readily available and cheap source for nutritional protein. As such, there is pressing demand from industry for improved protocols to determine chicken sex, especially in layer industry since only females can lay eggs. Extensive efforts are being dedicated to avoiding male chicks culling by developing in-ovo sexing detection methods. Any established in-ovo detection method will need to be validated by embryo genotyping. Therefore, there is a growing demand for fast, inexpensive, and precise method for proper discrimination between males and females in the poultry science community. Our aim with this study was to develop an accurate, high-throughput protocol for sex determination using small volumes of blood. We designed primers targeting the Hint-W gene within the W chromosome clearly distinguishing between males and females. In the interest of establishing an efficient protocol without the need for gel electrophoresis, crude DNA extraction without further purification was coupled with qPCR. We validated the accuracy of our method using established protocols and gonad phenotyping and tested our protocol with four different chicken breeds, day-nine embryos, day-old chicks and adult chicken. In summary, we developed a fast, cost-effective, and accurate method for the genotyping of sex chromosomes in chicken.

A review of the recent advances for the in ovo sexing of chicken embryos using optical sensing techniques

The culling of day-old male chicks has caused ethical and economic concerns. Traditional approaches for detecting the in ovo sex of chicken embryos involve opening the eggshell and inner membrane, which are destructive, time-consuming, and inefficient. Therefore, noncontact optical sensing techniques have been examined for the in ovo sexing of chicken embryos. Compared with traditional methods, optical sensing can increase determination throughput and frequency for the rapid sexing of chicken embryos. This paper presented a comprehensive review of the different optical sensing techniques used for the in ovo sexing of chicken embryos, including visible and near-infrared (Vis-NIR) spectroscopy, hyperspectral imaging, Raman spectroscopy, fluorescence spectroscopy, and machine vision, discussing their advantages and disadvantages. In addition, the latest research regarding different detection algorithms and models for the in ovo sexing of chicken embryos was summarized. Therefore, this paper provides updated information regarding the optical sensing techniques that can be used in the poultry industry and related research.

Trends in in ovo sexing technologies: insights and interpretation from papers and patents

Numerous researchers and institutions have been developing in ovo sexing technologies to improve animal welfare by identifying male embryos in an early embryonic stage and disposing of them before pain perception. This review gives a complete overview of the technological approaches reported in papers and patents by performing a thorough search using Web of Science and Patstat/Espacenet databases for papers and patents, respectively. Based on a total of 49 papers and 115 patent families reported until May 2023 worldwide, 11 technology categories were defined: 6 non-optical and 5 optical techniques. Every category was described for its characteristics while assessing its potential for application. Next, the dynamics of the publications of in ovo sexing techniques in both paper and patent fields were described through growth curves, and the interest or actual status was visualized using the number of paper citations and the actual legal status of the patents. When comparing the reported technologies in papers to those in patents, scientific gaps were observed, as some of the patented technologies were not reported in the scientific literature, e.g., ion mobility and mass spectrometry approaches. Generally, more diverse approaches in all categories were found in patents, although they do require more scientific evidence through papers or industrial adoption to prove their robustness. Moreover, although there is a recent trend for non-invasive techniques, invasive methods like analyzing DNA through PCR or hormones through immunosensing are still being reported (and might continue to be) in papers and patents. It was also observed that none of the technologies complies with all the industry requirements, although 5 companies already entered the market. On the one hand, more research and harmony between consumers, industry, and governments is necessary. On the other hand, close monitoring of the market performance of the currently available techniques will offer valuable insights into the potential and expectations of in ovo sexing techniques in the poultry industry.

Overview of Avian Sex Reversal

Sex determination and differentiation are processes by which a bipotential gonad adopts either a testicular or ovarian cell fate, and secondary sexual characteristics adopt either male or female developmental patterns. In birds, although genetic factors control the sex determination program, sex differentiation is sensitive to hormones, which can induce sex reversal when disturbed. Although these sex-reversed birds can form phenotypes opposite to their genotypes, none can experience complete sex reversal or produce offspring under natural conditions. Promising evidence indicates that the incomplete sex reversal is associated with cell autonomous sex identity (CASI) of avian cells, which is controlled by genetic factors. However, studies cannot clearly describe the regulatory mechanism of avian CASI and sex development at present, and these factors require further exploration. In spite of this, the abundant findings of avian sex research have provided theoretical bases for the progress of gender control technologies, which are being improved through interdisciplinary co-operation and will ultimately be employed in poultry production. In this review, we provide an overview of avian sex determination and differentiation and comprehensively summarize the research progress on sex reversal in birds, especially chickens. Importantly, we describe key issues faced by applying gender control systems in poultry production and chronologically summarize the development of avian sex control methods. In conclusion, this review provides unique perspectives for avian sex studies and helps scientists develop more advanced systems for sex regulation in birds.

Highly sensitive and quick in ovo sexing of domestic chicken eggs by two-wavelength fluorescence spectroscopy

The in ovo sexing of chicken eggs is a current task and a prerequisite to overcome the mass killing of male day-old chicks from laying lines. Although various methods have been developed and tested in recent years, practicable methods for sex determination are still missing which can be applicated in poultry hatcheries before the chicken embryo is capable of nociception and pain sensation. Optical spectroscopic methods enable an early determination of the sex. In this study, a novel method based on two-wavelength in ovo fluorescence excitation is described. More than 1600 eggs were examined. In ovo fluorescence was sequentially excited at 532 nm and 785 nm. The fluorescence intensities of the spectral regions behave inversely with respect to sex. It is shown that the observed sex-related differences in the fluorescence intensities are based on the embryonic hemoglobin synthesis. The accuracy of sex determination is 96% for both sexes. The hatching rate is not reduced compared to an equivalent reference group.

In ovo Feeding as a Tool for Improving Performance and Gut Health of Poultry: A Review

Early growth and development of the gastrointestinal tract are of critical importance to enhance nutrients' utilization and optimize the growth of poultry. In the current production system, chicks do not have access to feed for about 48-72 h during transportation between hatchery and production farms. This lag time affects early nutrient intake, natural exposure to the microbiome, and the initiation of beneficial stimulation of the immune system of chicks. In ovo feeding can provide early nutrients and additives to embryos, stimulate gut microflora, and mitigate the adverse effects of starvation during pre-and post-hatch periods. Depending on the interests, the compounds are delivered to the embryo either around day 12 or 17 to 18 of incubation and via air sac or amnion. In ovo applications of bioactive compounds like vaccines, nutrients, antibiotics, prebiotics, probiotics, synbiotics, creatine, follistatin, L-carnitine, CpG oligodeoxynucleotide, growth hormone, polyclonal antimyostatin antibody, peptide YY, and insulin-like growth factor-1 have been studied. These compounds affect hatchability, body weight at hatch, physiological functions, immune responses, gut morphology, gut microbiome, production performance, and overall health of birds. However, the route, dose, method, and time of in ovo injection and host factors can cause variation, and thereby inconsistencies in results. Studies using this method have manifested the benefits of injection of different single bioactive compounds. But for excelling in poultry production, researchers should precisely know the proper route and time of injection, optimum dose, and effective combination of different compounds. This review paper will provide an insight into current practices and available findings related to in ovo feeding on performance and health parameters of poultry, along with challenges and future perspectives of this technique.

Review: What are the challenges facing the table egg industry in the next decades and what can be done to address them?

There has been a strong consumer demand to take welfare into account in animal production, including table eggs. This is particularly true in Europe and North America but increasingly around the world. We review the main demands that are facing the egg industry driven by economic, societal and sustainability goals. We describe solutions already delivered by research and those that will be needed for the future. Already table egg consumption patterns have seen a major shift from cage to non-cage production systems because of societal pressures. These often feature free-range and organic production. These changes likely signal the future direction for the layer sector with the acceleration of the conversion of cage to barn and aviary systems with outdoor access. This can come with unintended consequences from bone fracture to increased disease exposure, all requiring solutions. In the near future, the laying period of hens will be routinely extended to improve the economics and environmental footprint of production. Many flocks already produce close to 500 eggs per hens in a lifetime, reducing the number of replacement layers and improving the economics and sustainability. It will be a challenge for scientists to optimize the genetics and the production systems to maintain the health of these hens. A major ethical issue for the egg industry is the culling of male day-old chicks of layer breeds as the meat of the males cannot be easily marketed. Much research has and will be devoted to alternatives. Another solution is elimination of male embryos prior to hatching by in ovo sexing approaches. The race to find a sustainable solution to early stage sex determination is on. Methods based on sex chromosomes, sexually dimorphic compounds and spectral properties of eggs containing male or female embryos, are being researched and are reviewed in this article. Other proposed solutions include the use of dual-purpose strains, where the males are bred to produce meat and the females to produce eggs. The dual-purpose strains are less efficient and do not compete economically in the meat or egg market; however, as consumer awareness increases viable markets are emerging. These priorities are the response to economic, environmental, ethical and consumer pressures that are already having a strong impact on the egg industry. They will continue to evolve in the next decade and if supported by a strong research and development effort, a more efficient and ethical egg-laying industry should emerge.

The Need for an Alternative to Culling Day-Old Male Layer Chicks: A Survey on Awareness, Alternatives, and the Willingness to Pay for Alternatives in a Selected Population of Dutch Citizens

A concerning by-product of producing laying hen chicks are the hatched male layer chicks. As a consequence of their inability to lay eggs, these male chicks are culled as day-old chicks in the hatchery. To find an alternative for this ethical dilemma (generally), three alternatives are under study, namely, in ovo sex determination, using dual-purpose breeds, and the rearing of layer cockerels. In order to assess the awareness of this practice and preference for one of the alternatives, we conducted an online survey of the Dutch public. Most of the 259 respondents completing the survey were highly educated woman (HEW, n = 143) versus others (REST, n = 86). The questionnaire was divided into six topics: (1) general knowledge of the poultry industry, (2) awareness of culling male layer chicks (CMC), and (3) its acceptability, (4) alternatives to CMC, (5) willingness to pay (WTP) for eggs without CMC, and (6) WTP for cockerel meat. Awareness about CMC was 52%, and its acceptability was rejected by 78% (HEW) and 67% (REST). The level of acceptability increased when more salient facts were given, and almost all respondents agreed that an alternative was needed (90% HEW, 84% REST). For both groups of respondents, more than 50% preferred in ovo sex determination over keeping the current practice or using dual-purpose breeds or male layers. Furthermore, the majority of respondents were willing to pay more than double the price for eggs without CMC being involved. Roughly 40% would not buy processed cockerel meat burgers, most likely due to their vegan or vegetarian diet. Of the remaining respondents, half were willing to pay the current price or 1 euro more for processed cockerel meat burgers. The most important factors when buying poultry meat or eggs without CMC were food safety, animal friendliness (welfare), and the environment; price was the least important factor. Despite the skewed respondents' background, the results of our survey show that consumers are willing to pay more for poultry products that do not require culling day-old male chicks.

Evaluation of Euthanasia Methods on Behavioral and Physiological Responses of Newly Hatched Male Layer Chicks

Newly hatched male layer chicks are considered as "by-products" in the egg industry and must be humanely euthanized at the hatchery. Instantaneous mechanical destruction (maceration) is the predominant euthanasia method applied in poultry hatcheries and is approved by the American Veterinary Medical Association (AVMA). However, maceration is not perceived by the public to be a humane means of euthanasia. The effects of alternative euthanasia methods, including carbon dioxide (CO₂) or nitrogen (N₂) inhalation, and a commercial negative pressure stunning system on behavioral and physiological responses of day-of-hatch male layer chicks, were evaluated in a field trial. Chick behaviors, including ataxia, loss of posture, convulsions, cessation of vocalization, and cessation of movement, were monitored. Serum hormones were assessed at the end of each of the alternative euthanasia treatments, including a control group allowed to breathe normal atmospheric air. The N₂ method induced unconsciousness and death later than the CO₂ and negative pressure methods, and increased serum corticosterone concentrations of neonatal chicks. Carbon dioxide inhalation increased serotonin concentrations as compared to controls, as well as the N₂ and the negative pressure methods. The behavioral and physical responses observed in this study suggest that both CO₂ inhalation and negative pressure stunning can be employed to humanely euthanize neonatal male layer chicks.

Euthanasia of laying hens: an overview

Euthanasia of an animal requires that its death occurs in as humane a manner as possible. There are three key scenarios for euthanasia in the egg industry: the humane destruction of day-old male chicks, euthanasia of individual birds, and the depopulation of flocks for disease control or because conventional transport and slaughter is uneconomic. For day-old chicks, instant mechanical maceration, although conditionally humane, presents a public perception problem. Submerging in CO2 gas is less confronting but is thought to be aversive to animals unless more expensive and harder to manage inert gases are incorporated. Future technologies involving pre-hatching sex determination or sex selection may largely solve the problem when fully developed. For the euthanasia of individual birds within the flock, manual cervical dislocation has been shown to be humane when performed by trained personnel who are willing to perform the procedure. Penetrating and non-penetrating mechanical devices that cause irreversible brain trauma are becoming more available and represent a humane alternative to cervical dislocation when properly placed and maintained. These devices may be less confronting for some staff to use than is cervical dislocation. For whole-flock euthanasia, the overwhelming requirements of disease control and public safety may override considerations of euthanasia. Whole-shed CO2 (or other gas combinations) and foam-based alternatives can be used, but have challenges in commercial settings. Modified atmosphere killing units or low atmospheric stunning systems are alternatives that overcome some of these practical problems, but do require birds to be handled.

Sexing chickens (Gallus gallus domesticus) with high-resolution melting analysis using feather crude DNA

Identification of sex in broiler chickens allows researchers to reduce the level of variation in an experiment caused by the sex effect. Broiler breeds commonly used in research are no longer feather sexable because of the change in their genetics. Other alternate sexing methods are costly and difficult to apply on a large scale. Therefore, a sexing method is required that is both cost effective and highly sensitive as well as having the ability to offer high throughput genotyping. In this study, high-resolution melting (HRM) analysis was used to detect DNA variations present in the gene chromodomain helicase DNA binding 1 protein (CHD1) on the Z and W chromosomes (CHD1Z and CHD1W, respectively) of chickens. In addition, a simplified DNA extraction protocol, which made use of the basal part of chicken feathers, was developed to speed up the sexing procedure. Three pairs of primers, that is, CHD1UNEHRM1F/R, CHD1UNEHRM2F/R, and CHD1UNEHRM3F/R, flanking the polymorphic regions between CHD1Z and CHD1W were used to differentiate male and female chickens via distinct melting curves, typical of homozygous or heterozygous genotypes. The assay was validated by the HRM-sexing of 1,318 broiler chicks and verified by examining the sex of the birds after dissection. This method allows for the sexing of birds within a couple of days, which makes it applicable for use on a large scale such as in nutritional experiments.

Look at that!-The effect pictures have on consumer preferences for in ovo gender determination as an alternative to culling male chicks

Gender determination in incubated eggs (in ovo) has the potential to substitute the highly discussed practice of culling male layer chicks. The aim of this study was to investigate the effect pictures have on peoples' preferences toward in ovo sexing at different stages of embryonic development and chick culling. For this purpose, an online survey was conducted with a representative sample of 482 respondents in Germany. A within-subject design with 2 choice experiments was used to investigate the influence pictures have on respondents' preferences and willingness to pay. The first-choice experiment contained plain text only; the second contained also pictures of a chick or the incubated eggs at the corresponding stages of development. Findings reveal that in ovo gender determination at each proposed day of incubation (d1, d4, and d9) was preferred to chick culling. In ovo screening on d1 and d4 was significantly preferred to d9. This preference for early gender determination increased significantly as a consequence to the provision of pictures. Results furthermore reveal that a high error rate of gender determination or the lack of a meaningful utilization of incubated eggs can decrease approval for in ovo gender determination to an extent, where no positive willingness to pay remains. Findings of this study are useful for stakeholders in poultry production when considering the implementation of in ovo gender determination as a morally admissible substitute to chick culling.

Chick Embryo Growth Modeling Using Near-Infrared Sensor and Non-Linear Least Square Fitting of Egg Opacity Values

Non-destructive monitoring of chick embryonic growth can provide vital management insights for poultry farmers and other stakeholders. Although non-destructive studies on fertility, hatching time and gender have been conducted recently, there has been no available method for embryonic growth observation, especially during the second half of incubation. Therefore, this work investigated the feasibility of using near-infrared (NIR) sensor-based egg opacity values—the amount of light lost when passing through the egg—for indirectly observing embryo growth during incubation. ROSS 308 eggs were selected based on size, mass and shell color for this experiment. To estimate the embryo size precisely, we fit various mathematical growth functions during incubation, based on the opacity value of incubated eggs. Although all the growth models tested performed similarly in fitting the data, the exponential and power functions had better performances in terms of co-efficient of determination (0.991 and 0.994 respectively) and RMSE to explain embryo growth during incubation. From these results, we conclude that the modeling paradigm adopted provides a simple tool to non-invasively investigate embryo growth. These models could be applied to resolving developmental biology, embryonic pathology, industrial and animal welfare issues in the near future.

Non-destructive sex-specific monitoring of early embryonic growth rate in light brown broiler eggs using light transmission and its correlation with hatching time and chick weight

1. Monitoring early embryonic growth rate (EGR) has significant economic and animal welfare benefits. This study focuses on monitoring sex-specific early EGR using light transmission, and correlating this with hatching time and chick weight. For broiler eggs in particular, spectral masking of the light brown eggshells needed to be addressed. This was done using longitudinal visible transmission spectroscopy combined with eggshell colour image analysis. 2. Prior to incubation, colour images of eggs were captured followed by daily measurements of transmission spectra of eggs from days one to nine of incubation. The sex of the eggs was subsequently verified 2 d after hatching. 3. To accurately and sensitively determine sex differences in EGR using light transmission, while minimising interference from eggshell colour and thickness, the ratio of longitudinal transmissions was determined to be most effective at 575 and 610 nm. 3. Embryonic growth was detectable from d 3 (72 h) of incubation, 24 h earlier than previously reported lateral transmission measurements. However, at this time, low blood levels meant that no significant sex-differences (P > 0.05) for the mean T575/T610 ratio were detectable. This may have been due, in part, to spectral masking from the light brown eggshells. At d 7, female embryos had a significantly lower (P < 0.05) mean T575/T610 ratio than males. 4. Although the T575/T610 ratio had low correlations with hatching time and hatch-weight of chicks, this could be a good starting point for further non-destructive investigations for such predictions. 5. In conclusion, the methodology had the sensitivity to differentiate sex-specific early EGR in broiler eggs, even with pigmented eggshells, and has the potential to advance precision hatchery management and poultry research.

Advances and challenges in genetic technologies to produce single-sex litters

There is currently a requirement for single-sex litters for many applications, including agriculture, pest control, and reducing animal culling in line with the 3Rs principles: Reduction, Replacement, and Refinement. The advent of CRISPR/Cas9 genome editing presents a new opportunity with which to potentially generate all-female or all-male litters. We review some of the historical nongenetic strategies employed to generate single-sex litters and investigate how genetic and genome editing techniques are currently being used to produce all-male or all-female progeny. Lastly, we speculate on future technologies for generating single-sex litters and the possible associated challenges.

Sex differences in serum steroid hormone levels during embryonic development in hen eggs

This experiment was conducted to explore the differences of serum steroid hormones with age and sex in hen eggs during incubation periods for identification of males and females. The concentrations of estrone (E1), estradiol (E2), estriol (E3), testosterone (T), androstenedione (A4), and dihydrotestosterone (DHT) in serum were measured by enzyme-linked immunosorbent assays in chicken embryos on 8, 10, 12, 14, and 16 D, respectively. During the development of chicken embryo, egg weight loss was closely related to age but no sex. However, it was found that both age and sex significantly affected hormones and had obviously more effect on androgens levels. Besides E2 and T, other steroids such as E1, A4, and DHT were also significantly correlated with sex (P < 0.05). Notably, the level of T and the ratio of T to E2 were significantly higher in males than females (P < 0.05). The ratio of E1 to E2 displayed different trends in different sexes, which increased in males but decreased in females. The distribution proportions of androgens and estrogens kept stable level during the late hatching periods of 12 to 16 D. The sex differences of steroids were more obvious at the late hatching stage through PCA. These suggested that the serum hormones differences in male and female embryos played a vital role in sexual differentiation. These findings not only provided the theoretical basis for sex determination of fertilized eggs in egg-laying hen strains, but also contributed to develop a non-invasive way to sex determination of fertilized eggs to meet the modern commercial application.

Consumer preferences for alternatives to chick culling in Germany

The use of highly specialized breeds in poultry production has led to the situation in which fattening layer-type males are not economically viable, when competing with the conventional broiler meat. The vast majority of male layer chicks are therefore culled soon after hatching. Ethical concerns about this practice have led to a public debate in a number of countries, and its tenor seems unambiguous: the practice should end. Political and industrial representatives have also promoted putting an end to chick culling. Two alternatives that are already available or soon to be in the market in a number of countries are dual-use poultry production and in ovo gender determination. However, the alternatives are also not free from controversy. The presented study analyzes consumer attitudes towards these 2 alternatives. A discrete choice experiment on eggs with different production attributes was conducted among a sample of 400 German citizens. Results from a latent class model show that there is considerable heterogeneity in preferences, which can be depicted in 5 consumer segments. Consumer segments differ significantly in socioeconomic characteristics and attitudes towards chick-culling alternatives. One segment decides mainly based on product price. However, 28% of the sample show no price sensitivity but choose based on other product attributes such as the preferred chick-culling alternative or egg type. We find wide approval for in ovo gender determination with no segment disapproving of the technology. When it comes to dual-use poultry, the type of husbandry of cockerels is crucial for the approval of this production scheme. Rearing male chicks in free-range husbandry is the preferred alternative for one segment representing 27% of the sample. Results provide empirical evidence for a diversified egg demand, indicating diverse expectations for poultry production in the future.

Rapid Label-Free Analysis of Brain Tumor Biopsies by Near Infrared Raman and Fluorescence Spectroscopy-A Study of 209 Patients

In brain surgery, novel technologies are continuously developed to achieve better tumor delineation and maximize the extent of resection. Raman spectroscopy is an optical method that enables to retrieve a molecular signature of tissue biochemical composition in order to identify tumor and normal tissue. Here, the translation of Raman spectroscopy to the surgical practice for discerning a variety of different tumor entities from non-neoplastic brain parenchyma was investigated. Fresh unprocessed biopsies obtained from brain tumor surgery were analyzed over 1.5 years including all patients that gave consent. Measurements were performed with a Raman microscope by medical personnel as routine activity. The Raman and fluorescence signals of the acquired spectra were analyzed by principal component analysis, followed by supervised classification to discriminate non-tumor tissue vs. tumor and distinguish tumor entities. Histopathology of the measured biopsies was performed as reference. Classification led to the correct recognition of all non-neoplastic biopsies (7/7) and of 97% of the investigated tumor biopsies (195/202). For instance, GBM was recognized as tumor with a correct rate of 94% if primary, and of 100% if recurrent. Astrocytoma and oligodendroglioma were recognized as tumor with correct rates of 86 and 90%, respectively. All brain metastases, meningioma and schwannoma were correctly recognized as tumor and distinguished from non-neoplastic brain tissue. Furthermore, metastases were discerned from glioma with correct rate of 90%. Oligodendroglioma and astrocytoma IDH1-mutant, which differ in the presence of 1p/19q codeletion, were discerned with a correct rate of 81%. These results demonstrate the feasibility of rapid brain tumors recognition and extraction of diagnostic information by Raman spectroscopy, using a protocol that can be easily included in the routine surgical workflow.

In Ovo Sexing of Chicken Eggs by Virus Spectroscopy

Recently, some new methods for sexing of chicken eggs by fluorescence and Raman spectroscopy through the shell membrane have been proposed. On the other hand, in another investigation, a new virus medical imaging has been suggested. In this research, summing over these considerations, a new technique for sexing of chicken eggs by virus spectroscopy through the shell membrane is proposed. It is shown that viruses outside the shell of egg can communicate with materials inside it and determine the gender of chick embryo and it’s evolutions.

Simple, sensitive and robust chicken specific sexing assays, compliant with large scale analysis

Chicken meat and eggs are important sources of food for the world population. The significant increase in food demand has pushed the food industry toward a rapid non-expensive production which in turn raises ethical issues. How chicken are cultivated and processed in food industry is no longer acceptable. Ethical and economical concerns emerging from chicken culling need to be solved in the near future. Indeed, in egg production industry, male chicken are killed at the age of 1-day post-hatching since they are not egg producers. A number of laboratory all over the world are looking for innovative non-invasive sexing methods to determine the sex of chicken in the early stages of the development before hatching. It will allow males' chicken elimination before the pain-feeling stages. In order to evaluate the efficiency of these methods, the scientific community need a reliable, easy to use and cost-effective in-ovo invasive sexing method. In this report, we developed two new invasive assays based on PCR and Q-PCR techniques respectively, which fulfil the above mentioned requirements. In the same line with other groups, we exploited the differences betweed males (ZZ) and females (ZW) chicken sexual chromosomes. We identified two genes, SWIM and Xho-I, on chromosome W and DMRT gene on chromosome Z allowing a clear discrimination between the two sexes using PCR and qPCR respectively. These two new genomic markers and their corresponding methods not only increase the accuracy but also reduce time and cost of the test compared to previously developed sexing methods. Depending on the technology available in the lab, one can choose between the two techniques requiring different machines and expertise.

A new chicken molecular sexing assay based on the Z chromosome dose and the MHM region

Birds have a ZZ and ZW sex chromosome system (male and female, respectively). On the short arm of the Z chromosome of Gallus gallus domesticus there is a repetitive region called MHM region, which is absent on the W chromosome, that causes a natural copy number difference of the MHM region between the sexes, making possible the development of a quantitative PCR (qPCR) sexing assay, based on the Z chromosome double dose. Twenty-seven samples of tissues from eight adult Gallus gallus domesticus (four males and four females) were used to establish the parameters of the MHM copy-number sexing assay. We blinded sexed 20 chicks using 140 samples from different tissues (heart, brain, gonad, kidney, lung, muscle, and blood). The success rate of the assay was 100% (140/140). It required small amounts of DNA (0.39 ng), opening the perspective to the use of the assay in studies in which the amount of available DNA is limited.

Swiss consumers' willingness to pay and attitudes regarding dual-purpose poultry and eggs

Chick culling is an efficient and cost-effective method in modern poultry farming, but it raises ethical concerns. Dual-purpose poultry (DP), in which males are fattened and females are used for egg production, is currently the most realistic alternative to culling, as in ovo sexing is not yet viable for practical application. Consumers' acceptance of DP products and their willingness to pay (WTP) for them have not been studied yet, and we expect that both aspects are closely related to the acceptance of and WTP for products from systems claiming beyond-conventional animal welfare, such as organic products. Results from a survey conducted among 402 consumers at 8 Swiss supermarkets revealed that the practice of chick culling was largely unknown (75% of respondents). Generally, respondents' knowledge about poultry production was low. The DP alternative was preferred to chick culling, but no preference emerged between DP and in ovo sexing. Furthermore, the WTP for DP products was proportionally lower for chicken than for eggs, probably because of the different price elasticity between these products. A regression analysis was used to determine the factors influencing consumers' WTP for DP products. Consumers' WTP was positively related to knowledge about poultry production, habits tied to purchasing organic or free-range poultry products, and familiarity with DP products. Therefore, a combination of the DP alternative with an organic label is recommended.

Rapid determination of the fat, moisture, and protein contents in homogenized chicken eggs based on near-infrared reflectance spectroscopy

Current analytical methods used for composition analysis of egg products are time consuming and laborious. We developed a near-infrared reflectance spectroscopy (NIRS)-based method to determine the fat, moisture, and protein contents in homogenized egg yolk and the moisture and protein contents in homogenized egg albumen to substitute for conventional methods. The coefficients of determination in the external validation set (R2P) were over 0.8 for all chemical compositions. The ratios of performance to standard deviation (RPD) were 4.38, 2.25, 2.28, 2.31, and 3.03 for fat, moisture, protein and moisture in the egg yolk, and protein in the egg albumen, respectively. Thus, NIR spectroscopy could be an efficient tool for quantitative analysis of the nutrients in chicken eggs.

Sexing of chicken eggs by fluorescence and Raman spectroscopy through the shell membrane

In order to provide an alternative to day-old chick culling in the layer hatcheries, a noninvasive method for egg sexing is required at an early stage of incubation before onset of embryo sensitivity. Fluorescence and Raman spectroscopy of blood offers the potential for precise and contactless in ovo sex determination of the domestic chicken (Gallus gallus f. dom.) eggs already during the fourth incubation day. However, such kind of optical spectroscopy requires a window in the egg shell, is thus invasive to the embryo and leads to decreased hatching rates. Here, we show that near infrared Raman and fluorescence spectroscopy can be performed on perfused extraembryonic vessels while leaving the inner egg shell membrane intact. Sparing the shell membrane makes the measurement minimally invasive, so that the sexing procedure does not affect hatching rates. We analyze the effect of the membrane above the vessels on fluorescence signal intensity and on Raman spectrum of blood, and propose a correction method to compensate for it. After compensation, we attain a correct sexing rate above 90% by applying supervised classification of spectra. Therefore, this approach offers the best premises towards practical deployment in the hatcheries.