This study evaluated the changes in eggshell mechanical properties, ultrastructure, calcium metabolism-related serum indices, and gene expression in eggshell gland during eggshell formation between laying ducks in the peak (young duck) and late phase (aged duck) of production. A total of 84 healthy young (31 wk of age) and 84 healthy aged (65 wk of age) Longyan laying ducks were each divided into 6 replicates of 14 birds, and caged individually. All the ducks were fed in one house with the same corn-soybean meal-based diet for 5 wk. The eggshell mechanical properties (shell proportion, thickness, breaking strength, and fracture toughness) and chemical components (matrix proteins, calcium, phosphorus, and magnesium) decreased in aged laying ducks ( P < 0.05). Shell structural indices: total thickness, effective thickness and its proportion decreased, whereas mammillary knob width and its proportion increased ( P < 0.05). The regulation values of early fusion, cuffing, caps, and total score of mammillary knobs were higher in aged laying ducks relative to the young ducks ( P < 0.05). During the initial, growth and terminal stages of eggshell formation, shell thickness and breaking strength (terminal), shell weight, and its proportion (terminal) decreased in aged laying ducks ( P < 0.05). Ultrastructural changes during shell formation indicated that the mammillary-knob density and effective thickness decreased ( P < 0.05). Decreases occurred in serum content of phosphorus (growth), and estradiol and calcium contents (terminal) ( P < 0.05). Relative expression of Ca 2+ transporter and HCO 3 − exchanger, and matrix proteins genes decreased in aged laying ducks ( P < 0.05) at all stages of eggshell formation. Collectively, the decreased incidence of early fusion and caps, increased thickness and width of mammillary knobs, and decreased effective thickness are the crucial differences leading to the compromised mechanical properties of eggshell in the late laying period. A disturbed regulation of calcium metabolism and uterine expression of ion transporters, especially for HCO 3 − exchange of aged laying ducks likely contribute to age-induced ultrastructural deterioration of the eggshell.

The study of border resilience is an effective means to analyze the development status of border cities. This study constructs a border city resilience assessment framework, measures the urban resilience level of 13 prefecture-level administrative regions in China’s northeastern border region from 2010 to 2019, reveals their temporal and spatial differentiation characteristics, analyzes the main obstacles, and proposes development strategies. This study reveals the following: (1) The overall resilience of the northeast border cities is at a medium level, and differences between regions and cities are large. (2) The resilience of the northeast border cities increased rapidly between 2010 and 2015, especially in the western area; the improvement effect was poor between 2015 and 2019, and except for the increased resilience of individual cities in the eastern area, the development of other cities was slow and some even declined. (3) At the city scale, the development potential, economic structure, residents’ security, and environmental governance capabilities are the main factors restricting improvement in the basic resilience of the northeast border cities. Insufficient national policy support and the poor development of neighboring countries have become obstacles to cities’ exclusive resilience.

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This study evaluated the effects of barley inclusion and glucanase supplementation on the productive performance and digestive function in laying ducks. The experiment used a randomized design with a 5 × 2 factorial arrangement of 5 graded levels of barley (0%, 15%, 30%, 45% and 60%) with or without 1.5 g/kg β-1,3-1,4-glucanase (15,000 U/kg). During the experimental period of 120 d, the weight and total number of eggs within each pen were recorded daily, and egg quality was determined every 4 wk. At the end of the experiment, 3 randomly selected ducks within each replicate were sacrificed, then duodenal digesta and jejunal mucosa was collected. Dietary inclusion of barley had no effects on egg production, daily egg mass or FCR, but supplementation with glucanase improved egg production and FCR ( P < 0.01). Barley did not affect feed intake of laying ducks, but glucanase tended to increase feed intake ( P = 0.09). Neither barley nor β-glucanase had effects on the egg quality variables, except for yolk color score, which was decreased with increasing barley supplementation. Glucanase, but not barley, increased the activity of chymotrypsin and amylase in duodenal digesta. Barley inclusion affected the activity of alkaline phosphatase and maltase in jejunal mucosa ( P < 0.05), but β-glucanase had no effects on the activity of these brush border enzymes. Barley inclusion increased the glucan content in duodenal digesta, but supplementation of glucanase to barley-based diet reduced digesta glucan content and reduced total volatile fatty acids and increased the proportion of acetic acid in cecal contents. The results indicate that, without glucanase, the optimal dietary barley level in the diets of laying ducks is about 13% for maximal production performance; glucanase supplementation of the barley diets improved production performance, probably through enhancing digestive function.