L. Zita

Technological quality of eggs in relation to the age of laying hens and Japanese quails

This investigation was carried out to evaluate certain egg quality characteristics of ISA Brown laying hens and Japanese quails (Coturnix coturnix japonica) in relation to their age. One hundred forty-four brown-egg ISA Brown laying hens and one hundred female quails were used in the study. A total of 1,678 eggs of laying hens and 2,060 eggs of Japanese quails were used during the experiment. The eggs for technological values were collected during two consecutive days in a 4-week period when the laying hens were from 20 to 60 weeks of age and the quails were from nine to 49 weeks of age. The results show that egg weight was affected by the age of the hens and quails (overall means 61.13 g and 12.52 g, respectively). Despite frequens fluctuations, as the age of the laying hens and quails increased, the yolk index and yolk proportion increased as well, while the albumen index, eggshell strength and shell thickness decreased. The increasing age of the hens also led to a decrease in egg shape index and eggshell proportion, but these parameters increased in the quails. A significantly higher proportion of albumen was found in the hens than in the quails, but of worse quality than in the quails as expressed by Haugh units score. The egg from ISA Brown hens had a darker yolk color than those from Japanese quails (5.90 vs. 4.87 in the La Roche scale).

Different breeds, different blood: Cytometric analysis of whole blood cellular composition in chicken breeds

While haematological variation is well known in birds, variation in avian breeds (distinct morphotypes of the same species) remains unexplored. Poultry breeds, in particular, may show interesting evolutionary patterns and economically-relevant physiological differences. We performed a comparative examination of blood cellular composition in five chicken (Gallus gallus domesticus) breeds: Araucana, Booted bantam, Czech, Minorca and Rosecomb bantam. In standard-environment-reared hens whole-blood flow cytometry revealed remarkable differences in most erythrocyte- and leukocyte-related parameters. We identified two extremes: Czech, a European breed, with a low heterophil/lymphocyte (H/L) ratio and high CD4+ levels, and Araucana, a South-American breed, with a high H/L ratio and high relative monocyte count. Such variation may reflect a combination of artificial and natural selection acting on health- and stress-related traits in domestic populations. Different breeds have evolved different immunological adaptations reflecting their original need to fight pathogens and physiological constraint resulting from dissimilar physiological trade-offs.

Effect of genotype and housing system on the concentration of cholesterol in egg yolk

The objective of the study was to assess the concentration of egg yolk cholesterol in Czech Hen and Oravka breeds kept in two different breeding systems (cages and litter). Egg-yield, hen day egg production and feed mixtures consumption were observed during the experimental period. The eggs for laboratory analysis were collected during 4-week periods, at 34, 38, 42, 46 and 50 weeks of age of the laying hens. Sample extracts were analyzed by gas chromatography employing mass selective detector. Only daily consumption of feed mixtures was significantly affected by genotype, housing systems and their interaction. The cholesterol concentration was significantly affected by genotype and housing system of laying hens. The highest average concentration of cholesterol in egg yolk was determined on litter (Oravka 11.64 mg/g and Czech Hen 10.84 mg/g) compared to cages. Simultaneously, the influences of age of laying hens and its interaction with the housing system were also demonstrated. The highest concentration of cholesterol was measured at 34 weeks of age of hens bred on litter. Conversely, the lowest concentration was found at 42 weeks of age of hens housed in cages. Other parameters were inconclusive. The results showed that the selection of a suitable genotype and housing system can significantly affect the concentration of cholesterol in egg yolk.

Domestic Fowl Breed Variation in Egg White Protein Expression: Application of Proteomics and Transcriptomics

Avian egg white is essential for protecting and nourishing bird embryos during their development. Being produced in the female magnum, variability in hen oviduct gene expression may affect egg white composition in domestic chickens. Since traditional poultry breeds may represent a source of variation, in the present study we describe the egg white proteome (mass spectrometry) and corresponding magnum transcriptome (high-throughput sequencing) for 20 hens from five domestic fowl breeds (large breeds: Araucana, Czech golden pencilled, Minorca; and small breeds: Booted bantam, Rosecomb bantam). In total, we identified 189 egg white proteins and 16391 magnum-expressed genes. The majority of egg white protein content comprised proteins with an antimicrobial function. Despite general similarity, Between-class Principal Component Analysis revealed significant breed-specific variability in protein abundances, differentiating especially small and large breeds. Though we found strong association between magnum mRNA expression and egg white protein abundance across genes, coinertia analysis revealed no transcriptome/proteome costructure at the individual level. Our study is the first to show variation in protein abundances in egg white across chicken breeds with potential effects on egg quality, biosafety, and chick development. The observed interindividual variation probably results from post-transcriptional regulation creating a discrepancy between proteomic and transcriptomic data.