This study was performed to investigate the effects of stocking density on performance, meat quality and tibia development in Pekin ducks reared on a plastic wire floor. A total of 372 healthy, 21-day-old, male ducks with similar body weight (BW) were randomly allotted to stocking densities of five (low), eight (medium) and 11 (high) birds/m . Each group had six replicates. Results showed that compared with the low density group, medium and high stocking density caused a decrease in final BW at 42 days old, and in average daily gain, European performance index (p < .01) and meat pH at 45 min postmortem (p < .001), and an increase of meat drip loss (p < .01). High stocking density resulted in an increase of feed/gain ratio (p < .001), but a decrease of tibia calcium (p < .01) and phosphorus content (p < .05). Meat color, shear force values, tibia size (weight, length, and width) and breaking strength were not significantly influenced by stocking density. In conclusion, stocking density over eight birds/m negatively affects growth performance, but meat quality and tibia development are not dramatically influenced. Based on this study, the stocking density of male Pekin ducks should be adjusted between five and eight birds/m .
An efficient copper-catalyzed double alkenylation of amides with (1Z,3Z)-1,4-diiodo-1,3-dienes is reported for the first time. The reactions proceed to afford di- or trisubstituted N-acylpyrroles in good to excellent yields using CuI as the catalyst, Cs2CO3 as the base, and rac-trans-N,N'-dimethylcyclohexane-1,2-diamine as the ligand.
Geckos show versatility by rapidly maneuvering on diverse complex terrain because they benefit from the distributed, setae-covered toes and thus the ability to generate reliable and adaptive attachment. Significant attention has been paid to their adhesive microstructures (setae), but the effectivness of the gecko’s adaptive attachment at the level of toes and feet remains unclear. Aiming to better understand geckos’ attachment, we first focused on the deployment of toes by challenging geckos to locomote on varying inclines. When the slope angle was less than than 30°, feet mainly interacted with the substrate using the bases of toes and generated anisotropic frictional forces. As the slope angle increased to 90°, the participation of toe bases was reduced. Instead, the setae contribution increased for the middle three toes of the front feet and for the first three toes of the hind feet. As the incline changed from vertical to inverted, the adhesive contribution of the toes at the front feet became more equal, whereas the effective adhesion contact of the hind feet gradually shifted to the toes oriented rearward. Second, a mathematical model was established and then suggested the potential advantages of distributed control among toes to regulate foot force. Finally, a physical foot model containing five compliant, adjustable toes was constructed and validated the animal discoveries. By using the gecko toes’ control strategies, the artificial foot demonstrated diverse behavior regulating attachment forces. The success of the foot prototype not only tested our understanding of the mechanism of biological attachment, but also provided a demonstration for the design and control of gecko-inspired attachment devices, grippers, and other manipulators.
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