Dietary compounded traditional Chinese medicine residue meal improves laying performance, egg quality, and gut barrier integrity in late-phase laying hens

This study aimed to investigate the impact of compounded traditional Chinese medicine residue meal (CCMR) on late-phase laying hens, focusing on laying performance, egg quality, albumen gel properties, antioxidant status, immunity, and intestinal barrier function. A total of 192 healthy 56-week-old Xinyang black-feathered laying hens with comparable body weights were randomly divided into two dietary treatment groups, with six replicates of 16 birds per group. The hens were fed a corn-soybean meal-based diet, either without supplementation (CON group) or supplemented with 3 g/kg CCMR (CCMR group), for 9 weeks. Results showed that CCMR tended to reduce feed conversion ratio (FCR; weeks 1-4, P = 0.074; weeks 1-8, P = 0.097) and broken egg rate (weeks 1-4, P = 0.082; weeks 1-8, P = 0.065) in late-laying hens. In contrast to the CON, CCMR significantly enhanced eggshell thickness (P = 0.078), strength (P = 0.067) and ratio (P < 0.01) at week 4, as well as eggshell thickness (P < 0.05), ratio (P < 0.05) with a trend toward eggshell strength (P = 0.087) and Haugh Unit (P < 0.05) at week 8 of the experiment. CCMR markedly enhanced (P < 0.05) hardness, gumminess, LH, E2 compared to the CON. Dietary CCMR significantly reduced serum TBIL and γ-GT (P < 0.05), and increased serum Ca (P = 0.058), along with significant elevations in PTH and CT (P < 0.05). Dietary CCMR markedly reduced levels of MPO and MDA (P < 0.05), with a trend toward lower H₂O₂ (P = 0.061). It also increased serum activity of SOD, GSH-Px and CAT (P < 0.05), while T-AOC showed a marginal increase (P = 0.070). Additionally, CCMR up-regulated duodenal and jejunal expression GSH-Px, CAT and SOD genes (P < 0.05). CCMR supplementation marginally increased serum LZM (P = 0.066) and IgG (P = 0.071), significantly elevated IgM, IFN-γ and IL-2 levels (P < 0.05), and reduced TNF-α, IL-6 (P < 0.05). Additionally, CCMR supplementation up-regulated duodenal (P < 0.05) and ileal (P < 0.01) IFN-γ gene expression, while down-regulated iNOS, NF-κB, TNF-α and IL-1β expression in the small intestine (P < 0.05). CCMR supplementation improved duodenal morphology, significantly increasing villus height (VH; P < 0.05) and tending to elevate the villus height-to crypt depth ratio (VCR; P = 0.096). It also up-regulated tight junction protein expression (ZO-1, occludin, claudin-2, E-cadherin; all P < 0.05), with marginal effects on claudin-1 (P = 0.061) and mucin-2 (P = 0.058) expression. CCMR supplementation improved jejunal morphology by significantly increasing the mRNA expression of occludin, claudin-1, claudin-2 (P < 0.05), with a marginal effect on ZO-1 expression (P = 0.096). Furthermore, it also improved ileal morphology by decreasing crypt depth (CD) and modulating tight protein expression, significantly increasing claudin-1 (P < 0.05), with marginal effects on ZO-1 (P = 0.078) and claudin-2 (P = 0.061). Dietary supplementation with 3 g/kg CCMR improves laying performance, egg quality, albumen gel properties in late-laying hens, likely through regulating reproductive hormones, enhancing antioxidant capacity, strengthening immune response, and supporting intestinal barrier function.