The elimination of antibiotic growth promoters from poultry production has increased demand for alternative feed additives. This study evaluated the impact of several gastrointestinal-stabilising formulations (medium-chain fatty acids, probiotics, and organic acids) on the productivity and egg quality of laying hens. A total of 90 (Lohmann Brown) laying hens were randomly assigned to 5 treatment groups, with 6 replicates of three hens each (18 hens per group). The control group (C) received a basal diet, whereas the experimental groups were additionally supplemented with 0.2% medium-chain fatty acids (A), 0.1% probiotics (L), a 0.1% blend of calcium butyrate, calcium lactate, and bentonite encapsulated in vegetable fats (BE), or 0.05% calcium butyrate encapsulated in vegetable fats (BP). During the 56-day trial, additives exerted no significant effect on performance in hens aged 30–33 weeks. However, in hens aged 34–37 weeks, medium-chain fatty acids significantly increased egg weight and improved feed conversion ratio compared to controls. All additives also markedly increased eggshell thickness in younger hens (30–33 weeks) (P < 0.05). Additionally, significantly higher Haugh unit values (P < 0.05) were recorded for the L, A, and BE groups compared to the C group. For the 34–37 week period, eggs from the A, BE and BP groups had significantly greater shell thickness (P < 0.05) compared to the C group. No significant differences in bird mortality were observed between the groups. These results suggest that medium-chain fatty acids and organic acid salts can effectively support gastrointestinal health and egg quality as antibiotic alternatives in laying hens.