The objective of this study was to evaluate different methods used for estimating cook loss in broiler breast fillets (pectoralis major). Two experiments were conducted. In the first experiment, intact fillets were weighed, cooked to 75°C, and then subjected to 1 of 3 postcook handling treatments: cooling for 5 min at room temperature before reweighing (5-minute), cooling at room temperature until they reached room temperature before reweighing (RT), or cooling in ice water until they reached room temperature before reweighing (IW). In the second experiment, breast fillet portions were used to compare the effects of endpoint temperature (53°C, 57°C, 68°C, 75°C, or 90°C) on cook loss estimation by the 5-minute and RT methods. Breast fillets were collected from local chicken processing plants and trimmed to similar weight prior to cooking. Cook loss, cook loss retention, and total cook loss after 24 h in cooked fillets were measured for comparisons. Data showed that cook loss (<17%) and total loss (19.3%) estimated with the IW method were lower (P < 0.05) than those with the 5-minute and RT methods (19–21% for cook loss and 21.1–21.3% for total loss), which did not differ from each other. When the endpoint temperature was ≥75°C, no differences in cook loss estimates or moisture loss were noted between the 5 min and RT methods (after 3 h cooling). However, when the temperatures were 53°C to 75°C, cook loss estimations were significantly different (P < 0.05) between the 5 min and RT methods (more than 4%). Reduced endpoint temperature resulted in increasing differences (from less than 5% to more than 9%) in cook loss estimates. These results demonstrate that endpoint cooking temperature and postcooking sample handling methods may affect cook loss estimates in broiler breast meat.

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.

Poultry welfare has been extensively studied; however, there is a lack of rigorous scientific knowledge relating to the different aspects of welfare factors and how this may contribute to the production quantity and product quality as well as the welfare of chickens. Therefore, we conducted an integrated study to compare welfare factors in chickens by providing free dietary choice under cage rearing, and further comparing cage rearing with free-range rearing. One hundred chickens each were allocated to a cage rearing group with conventional feeding (CC), a cage rearing group with free dietary choice of mealworms (FDM), a cage rearing group with free dietary choice of mealworms and fresh grass (FDMG), and a free-range rearing system group with free dietary choice of mealworms and fresh grass (FRMG). Results showed that under cage rearing, free dietary choice contributed to better meat quality and gait score, higher values of blood platelets, and a richer gut microbial composition, but poorer egg production than CC chickens. As compared to FDMG, FRMG chickens showed better meat quality, gait score, and feather conditions, as well as a richer gut microbial composition; however, they had poorer egg production and a poorer foot pad and foot feather condition. We conclude that free dietary choice and free-range rearing systems improve the product quality, gait score, and microbial richness of 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.

Unique metabolites contribute to the performance of meat flavor and potential function. In this study, UHPLC-Q Exactive HF-X-based metabolomics and multivariate analysis were applied to explore the characteristic metabolites in the breast meat of Beijing-You chicken (BYC) aged 150, 300, and 450 days (D150, D300, and D450). Based on the criteria of variable importance in the projection (VIP) > 1 and p < 0.05, a total of 154 and 97 differential metabolites (DMs) were screened out compared with D450 (D450 vs. D150, D450 vs. D300), respectively. In general, the relative content of carnosine, L-L-homoglutathione, demethyloleuropein, neohesperidin dihydrochalcone, 7-chloro-2-(3,4-dimethoxyphenyl)-3,5-dihydroxy-6,8-dimethoxy-4H-chromen-4-one, glycerophospholipids, exhibited the highest abundance at D450, while balenine, anserine, L-beta-aspartyl-L-leucine, glutathione, oxidized glutathione, stearoylcarnitine, ganoderic acid alpha, oleuroside, Lysoglycerophospholipid species (LGP) presented a downward trend with age. These 210 DMs were involved in 10 significantly enriched pathways related to the synthesis and metabolism of amino acids, peptides, and glycerophospholipid, such as glutathione metabolism, histidine metabolism, glycerophospholipid metabolism, arginine biosynthesis, tyrosine metabolism, and lysine degradation. In conclusion, this work could not only facilitate a better understanding of the differences of chicken flavor and benefit properties with age, but also provide potential valuable bioactive compounds for further research.

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.