Background: Broken-shell eggs in aged laying hens cause great losses to the egg industry. Saccharomyces cerevisiae yeast may improve shell quality by modulating intestinal health and oviduct function. Objectives: This study was carried out to determine the effects of supplementing Saccharomyces cerevisiae yeast extract (SYE) to the diets of aged commercial laying hens. Methods: A total of 192 Shaver White laying hens aged 105–116 weeks were allocated to four dietary levels of SYE (0, 1.0, 2.0, 3.0 g/kg diet), with 6 replicates of 8 birds each. The experiment was performed in a randomized complete block design. Results: The use of different levels of SYE caused a significant linear and quadratic increase in the percentage of laying and daily egg mass production (p < 0.05). Feed intake (FI) in the 3 g/kg treatment was significantly higher than the control treatment in 113–116-week period (p < 0.05). The percentage of eggshell and shell thickness at 105–116 weeks of age (total period) in the 3 g/kg treatment was significantly higher than the control treatment (p < 0.05). Orthogonal comparison of the supplemented SYE against the control treatment also showed that the use of SYE in the diet significantly increased (p < 0.05) the percentage of shell (12.2% vs. 11.4%) and eggshell thickness (0.384 vs. 0.362 mm) compared to the control treatment. Conclusions: The use of different levels of SYE did not have a significant effect on production performance indicators in old laying hens of the Shaver White strain. It significantly increased the thickness and relative weight of eggshell. Supplementing SYE 3 g/kg diet significantly increased the average eggshell percentage and shell thickness.

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