Thigh meat from Cobb 500 broiler (Cobb) and Beijing-You chicken (BYC) at marketable age were compared to explore the impact of growth rate on meat quality. BYC had a higher water capacity, as well as lower shear forces and IMF content than Cobb, indicating that the growth rate has a significant influence on meat quality. Additionally, 144 upregulated and 44 downregulated differential metabolites were identified using gas chromatography mass spectroscopy (GC-MS) and liquid chromatography mass spectrometer (LC-MS). Moreover, we found a significant difference between the dominant expression of metabolites in the two genotypes. The highly expressed metabolites in Cobb were amino acids and their derivatives, including l-citrulline, dimethylglycine, 1,4-butanediamine, alanine, and creatine. In contrast, BYC deposited more bioactive compounds, such as, α-linolenic acid, linoleic acid, eicosapentaenoic acid, anserine, and taurine. These results indicate that meat quality and metabolite profiles differ greatly between fast- and slow-growing chickens.

The physical properties, free amino acids, and metabolites of Beijing-You chicken (BYC) breast meat aged 90, 120, and 150 days were analyzed to investigate the flavor changes with age. The shear force and intramuscular fat increased from 90 to 120 days significantly. The contents of total free amino acids and essential amino acids decreased from 90 to 120 days significantly. No significant differences were detected between 120 and 150 days. The contents of sweet amino acids, bitter amino acids, and umami amino acids showed no significant differences between different ages. In addition, GC-MS and LC-MS were integrated for metabolite detection in breast meat. A total of 128, 142, and 88 differential metabolites were identified in the comparison groups of 120 d vs. 90 d, 150 d vs. 90 d, and 150 d vs. 120 d. Amino acids and lipids were the main differential metabolites. The pathway analysis showed that arginine biosynthesis, histidine metabolism, purine metabolism, and cysteine and methionine metabolism were the main pathways involved in flavor formation during BYC development. It was also found that the metabolites associated with flavor, such as methionine, cysteine, glucose, anserine, arachidonic acid, and glycerol 1-phosphate, were significantly affected by age.

Chicken age contributes to the meat characteristics; however, knowledge regarding the pathways and proteins associated with meat quality and muscle development are still scarce, especially in chicken thigh meat. Hence, the objective of this study was to elucidate the intricate relationship between these traits by liquid chromatography mass spectrometry at three different ages. A total of 341 differential expressed proteins (DEPs) were screened out (fold change ≥ 1.50 or ≤0.67 and p < 0.05) among 45 thigh meat samples (15 samples per age) of Beijing-You chicken (BYC), collected at the age of 150, 300, or 450 days (D150, D300, and D450), respectively. Subsequently, based on the protein interaction network and Markov cluster algorithm (MCL) analyses, 91 DEPs were divided into 26 MCL clusters, which were associated with pathways of lipid transporter activity, nutrient reservoir activity, signaling pathways of PPAR and MAPK, focal adhesion, ECM-receptor interaction, the cell cycle, oocyte meiosis, ribosomes, taurine and hypotaurine metabolism, glutathione metabolism, muscle contraction, calcium signaling, nucleic acid binding, and spliceosomes. Overall, our data suggest that the thigh meat of BYC at D450 presents the most desirable nutritional value in the term of free amino acids (FAAs) and intramuscular fat (IMF), and a series of proteins and pathways associated with meat quality and development were identified. These findings also provide comprehensive insight regarding these traits across a wide age spectrum.

Lutein- and astaxanthin-fortified eggs can greatly improve both nutritional and economic values of eggs. High doses of lutein and astaxanthin are often supplemented in hen diets to rapidly accumulate lutein and astaxanthin in eggs. In this study, an additional 100, 200, and 400 mg/kg lutein and astaxanthin were added in hen diets to explore the effects of high-dose lutein and astaxanthin on egg quality, egg production, and carotenoid deposition in eggs, which remains unclear. The results showed that high-dose lutein and astaxanthin supplementation had no significant impact on laying rates and egg quality, except for markedly improving yolk color. Additionally, a quantitative profile of carotenoids in egg yolk was performed through liquid chromatography–mass spectrometry. A total of 26 carotenoids were detected including 14 whose concentrations exceed 0.1 µg/g. Notably, the zeaxanthin content in yolk decreased with the increase in levels of lutein supplementation. Conversely, the content of lutein, zeaxanthin, 5,6 epoxy-lutein-caprate-palmitate in yolk decreased as astaxanthin supplementation increased. These findings suggest that high doses of lutein and astaxanthin supplementation may competitively inhibit the deposition of other carotenoids in egg yolk. Overall, this study suggests that during the production of functional eggs enriched with lutein and astaxanthin, it is important to consider the interaction effects among different carotenoids.

Due to the effects of pigment deposition and microstructure, the color of eggshells may influence the quality traits and hatchability of eggs. These traits are critical for breeding efficiency and economic outcomes in poultry production. Herein, Beijing-You chicken eggs were used as a model to investigate the effects of eggshell color due to their color-related polymorphism. A total of 4422 eggs were analyzed for their hatchability, categorized by storage duration and eggshell color. Results revealed that white-shelled eggs exhibit significantly lower hatchability and higher early embryo mortality compared to other colors, particularly after long-term storage. Purple-shelled eggs demonstrated superior eggshell quality, including higher strength, thickness, and weight, as well as better internal egg quality indicators such as thick albumen height, Haugh units, and yolk color. Eggshell translucency showed a positive correlation with storage time and egg weight loss at all shell color types, with higher translucency levels associated with greater weight loss over time. This study examines associations between eggshell color, hatchability, translucency, and quality traits.