News Article | September 6, 2016
For chickens bred to lay eggs, being male is a gloomy prospect. These cockerels develop too slowly to be raised for meat, so they are usually killed within days of hatching by methods including gassing and grinding. The practice culls billions of chicks each year, raising ethical concerns for consumers and animal rights advocates. As a result, both United Egg Producers, the U.S. industry group that represents most hatcheries for egg-laying hens, and the German government have pledged to end the practice in coming years, or once an alternative is available. Now researchers have developed an approach that could help speed this transition: using spectroscopy to identify the sex of a developing chicken embryo while it’s still in the egg (Anal. Chem. 2016, DOI: 10.1021/acs.analchem.6b01868). The method, which has up to 95% accuracy, could allow hatcheries to cull male chick embryos just three days into development, before they are sensitive to pain. Currently, the sex of chicks can be determined before they hatch by sampling hormone levels or DNA from within the egg after removing a piece of shell. But hormonal tests must be done on about day nine of development, and chicks become sensitive to pain at about day seven, says Roberta Galli of Dresden University of Technology. Moreover, these testing methods require taking a sample from each egg, followed by chemical analysis, which may not be feasible on an industrial scale. Galli and her colleagues wanted to develop a less invasive method that could be applied earlier in development. The team has used Raman spectroscopy for other sensitive biomedical applications, so they thought the approach might be able to determine sex, which imparts differences to blood biochemistry. Male blood has different protein and sugar profiles and about 2% more DNA than female blood. The method the team developed uses a laser to cut a 15-mm-diameter circle in the end of an eggshell. When the researchers remove the shell piece on day three of development, the embryo’s blood vessels are visible. They shine near-infrared light on the vessels and detect the scattering with a Raman spectrometer; the spectrum is rapidly assigned to a sex based on algorithms the team developed. For 101 eggs whose sex was also determined by DNA test, the algorithm correctly identified embryo sex in 90% of cases. However, Galli says they have since optimized the system, nudging the accuracy to 95%—closer to the 98% accuracy of manual sex determination used in industry based on examining the feathers or genitals. After the analysis, the researchers close up the egg with surgical adhesive tape and allow development to continue. About 81% of the eggs they tracked after the test hatched and developed normally, compared to 92% of control eggs, though other control studies report hatching rates of 84–90%. The team’s lab system can process two to three eggs per minute—much slower than expert chick sexers, who can work at five to eight times that rate. But the team is building an industrial prototype to automate the process and has partnered to test it with Lohmann Tierzucht, a major commercial producer of egg-laying hens in Germany, where demand for an alternative to chick culling is high. Right now the team does not have a cost estimate for the prototype, Galli says, but the fact that the method requires minimal consumable products may keep expenses down. Rodrigo Gallardo, an expert in poultry biology at the University of California, Davis, calls the technique “very promising” because it can be applied so early in development and is less invasive than other methods. However, he says, it “needs further development and refinement to be used in the poultry industry,” including lowering the processing time, improving the accuracy, and ensuring that the method does not harm or contaminate developing chicks.
Dunn I.C.,Roslin Institute |
Rodriguez-Navarro A.B.,University of Granada |
McDade K.,University of Glasgow |
Schmutz M.,Lohmann Tierzucht |
And 4 more authors.
Animal Genetics | Year: 2012
The size and orientation of calcium carbonate crystals influence the structure and strength of the eggshells of chickens. In this study, estimates of heritability were found to be high (0.6) for crystal size and moderate (0.3) for crystal orientation. There was a strong positive correlation (0.65) for crystal size and orientation with the thickness of the shell and, in particular, with the thickness of the mammillary layer. Correlations with shell breaking strength were positive but with a high standard error. This was contrary to expectations, as in man-made materials smaller crystals would be stronger. We believe the results of this study support the hypothesis that the structural organization of shell, and in particular the mammillary layer, is influenced by crystal size and orientation, especially during the initial phase of calcification. Genetic associations for crystal measurements were observed between haplotype blocks or individual markers for a number of eggshell matrix proteins. Ovalbumin and ovotransferrin (LTF) markers for example were associated with crystal size, while ovocleidin-116 and ovocalyxin-32 (RARRES1) markers were associated with crystal orientation. The location of these proteins in the eggshell is consistent with different phases of the shell-formation process. In conclusion, the variability of crystal size, and to a lesser extent orientation, appears to have a large genetic component, and the formation of calcite crystals are intimately related to the ultrastructure of the eggshell. Moreover, this study also provides evidence that proteins in the shell influence the variability of crystal traits and, in turn, the shell's thickness profile. The crystal measurements and/or the associated genetic markers may therefore prove to be useful in selection programs to improve eggshell quality. © 2011 Stichting International Foundation for Animal Genetics.
Utilization of laying-type cockerels as "coquelets": Influence of genotype and diet characteristics on growth performance and carcass composition [Nutzung männlicher legehybriden als stubenküken: Der einfluss der herkunft und der futtervarianten auf wachstumsleistung und schlachtkörperzusammensetzung]
Koenig M.,Max Rubner Institute |
Hahn G.,Max Rubner Institute |
Damme K.,Bavarian Institute for Agriculture |
Schmutz M.,Lohmann Tierzucht
Archiv fur Geflugelkunde | Year: 2012
The aim of the study was to find an alternative to the present culling of one-day old male layer chicks in the contextof laying hen reproduction. The development of a new ethi-cally justifiable production system for the rearing of laying-type cockerels to produce coquelets could be a solution of this ethical problem. To this end, a project was initiated to determine economic efficiency and suitable managementfactors of coquelet production. After appropriate genotypesfor laying-type cockerels had been determined in a preceding trial, we analyzed fattening performance and carcassquality in order to evaluate the potential to optimize coque-let production. The experiment was performed with the medium-heavygenotype Lohmann Brown (LB) and the light genotypeLohmann Selected Leghorn (LSL). The cockerels were rearedon deep litter and were fed on standard diets for broilers (BD) or laying-hens (LHD). After a rearing period of 49 days, fattening performance and carcass quality were analyzed with genotype and feeding regime and their interactions as main effects. The development of body weight is more influenced by feeding regime than by genotype. Further results of growth performance, feed conversion and carcass quality showed the influence of the two different feeding regimes. Standard BD appeared to be more appropriate for cockerel feeding because it improved the fattening performance compared to LHD. However, carcass composition was not affected by the different feeding regimes. But with regard to tissue composition and percentage ofvaluable parts, cockerel genotypes differed. In most aspectsof carcass quality, the medium-heavy LB performed better than the light LSL. The results of this study outline the economic feasibility of coquelet-production. The project thus contributes to link the production of a high-quality niche product with the solution of an ethical problem in animal production. © Verlag Eugen Ulmer, Stuttgart.
Bain M.M.,University of Glasgow |
McDade K.,University of Glasgow |
Burchmore R.,University of Glasgow |
Law A.,Roslin Institute |
And 4 more authors.
Animal Genetics | Year: 2013
The cuticle is a proteinaceous layer covering the avian egg and is believed to form a defence to microorganism ingress. In birds that lay eggs in challenging environments, the cuticle is thicker, suggesting evolutionary pressure; however, in poultry, selection pressure for this trait has been removed because of artificial incubation. This study aimed to quantify cuticle deposition and to estimate its genetic parameters and its role on trans-shell penetration of bacteria. Additionally, cuticle proteins were characterised to establish whether alleles for these genes explained variation in deposition. A novel and reliable quantification was achieved using the difference in reflectance of the egg at 650 nm before and after staining with a specific dye. The heritability of this novel measurement was moderate (0.27), and bacteria penetration was dependent on the natural variation in cuticle deposition. Eggs with the best cuticle were never penetrated by bacteria (P < 0.001). The cuticle proteome consisted of six major proteins. A significant association was found between alleles of one of these protein genes, ovocleidin-116 (MEPE), and cuticle deposition (P = 0.015) and also between alleles of estrogen receptor 1 (ESR1) gene and cuticle deposition (P = 0.008). With the heritability observed, genetic selection should be possible to increase cuticle deposition in commercial poultry, so reducing trans-generational transmission of microorganisms and reversing the lack of selection pressure for this trait during recent domestication. © 2013 The Authors, Animal Genetics © 2013 Stichting International Foundation for Animal Genetics.