Supplementation effects of feed additive containing eggshell, Schisandra chinensis by-products combined with multi-probiotics strains in laying hens

Eggshell waste and Schisandra chinensis by-products are natural sources rich in beneficial nutrients and bioactive compounds. However, their combined effects with multi-probiotics on poultry productivity and health remain unexplored. This study assessed the immediate effects of a feed additive—eggshell waste (ES), Schisandra chinensis by-product (SC), and multi-probiotics (M)—administered for four weeks to aged laying hens before slaughter, evaluating the improvements of laying performance, egg quality, blood characteristics, visceral organs, tibia, and cecal microbiota. A total of 216 Hy-line Brown laying hens (70-week-old) were assigned to four dietary treatments consisting of 9 replicates of 6 birds in a completely randomized design. The ESM of feed additive consisted of 40% eggshell, 5% SC, and 10⁹ -10¹¹ CFU/g of multi-probiotic strains including Bacillus subtilis, Bacillus licheniformis, Saccharomyces cerevisiae, Lactobacillus plantarum, and supplemental nutrient premix. The treatment groups were as follows: corn–soybean meal-based basal diet (control); basal diet + 0.1% ESM; basal diet + 0.2% ESM, basal diet + 0.4% ESM. The total egg productivity rate during the experiment period tended to improve in ESM 0.2%, as compared with the control. The ESM 0.1% group increased egg weight (p < 0.05) while ESM 0.1% and ESM 0.2% tended to increase egg mass, compared to the control (p = 0.051). However, there was no significant difference in egg weight, feed intake, feed conversion ratio, and egg quality among the treatments. Furthermore, blood characteristics did not differ between the treatments, except for the total cholesterol contents, which was higher in ESM 0.4% treatment than the control (p< 0.05). ESM 0.4% supplementation showed a tendency for higher calcium, compared to the control. ESM 0.4% supplementation showed higher bone mineral density (BMD) of the tibia neck than the control (p< 0.01). All three ESM groups demonstrated a significant decrease in the abundance of Bacteroidaceae (p< 0.05), and an increase in the abundance of Lactobaillaceae at the family level (p< 0.01). In conclusion, ESM fed hens showed beneficial effects on the egg weight, egg mass, BMD of tibia neck, and cecal microbiota in laying hens.