Abstract: [Objective] To investigate the effects of tributyrin （TB） and glycerol monolaurate （GML） complex on production performance, egg quality, serum biochemical parameters, and serum hormone levels in laying hens in the late laying period. [Methods] A total of 952 healthy 80-week-old Hy-Line Sonia laying hens were randomly divided into a control group （basal diet） and an experimental group （basal diet supplemented with 1,000 mg/kg TB and GML complex）. Each treatment consisted of 17 replicates, with 28 hens per replicate. The trial lasted for 8 weeks. Feed intake, egg number, and egg weight were recorded on a per-replicate basis to calculate average egg weight, laying rate, average daily feed intake, feed-to-egg ratio, and average egg production. At the end of the 4^th and 8^th weeks, egg samples were collected to assess egg quality parameters, and blood samples were collected to measure serum biochemical parameters and hormone levels. [Results] ① Dietary supplementation with the TB and GML complex showed a tendency to increase the laying rate from weeks 5 to 8 （P=0.098） and reduce the feed-to-egg ratio （P=0.055）. ②Compared to the control group, the experimental group exhibited a highly significant （P<0.01） reduction in water spot egg scores and a significant （P<0.05） improvement in eggshell strength at the 4^th week. ③Relative to the control group, dietary supplementation with the TB and GML complex significantly （P<0.05） reduced serum lactate dehydrogenase activity at the 4^th week and showed a tendency to decrease serum triglyceride levels （P=0.052）. At the 8^th week, the experimental group had significantly （P<0.05） higher serum levels of total protein, albumin, calcium, and total cholesterol compared to the control group.④Compared to the control group, the experimental group showed highly significant （P<0.01） increases in follicle-stimulating hormone （FSH） and luteinizing hormone （LH） levels, as well as a significant （P<0.05） increase in estradiol levels at the 4^th week. At the 8^th week, the experimental group exhibited highly significant （P<0.01） increases in FSH and estradiol levels and a significant （P<0.05） increase in LH levels. No significant （P>0.05） differences were observed in progesterone levels between the two groups. [Conclusion] In summary, dietary supplementation with the TB and GML complex improved serum hormone levels and eggshell quality in late-laying hens.

Key words: tributyrin, glycerol monolaurate, laying hens, production performance, egg quality, hormones