Effects of chili meal supplementation on productive performance, intestinal health, and liver lipid metabolism of laying hens fed low-protein diets

This study aimed to explore the effects of chili meal (CM), a by-product of chili pepper oil extraction, on the productive performance, intestinal health, and lipid metabolism of laying hens fed low-protein (LP) diets. A total of 384 Hy-Line brown laying hens (32 weeks old) were divided into six groups: control (CON) diet with 16.5 % crude protein (CP), LP diet with 15 % CP, and LP diets supplemented with 3 %, 5 %, 7 %, and 9 % CM. Results showed that dietary CM supplementation of up to 5 % did not negatively affect the productive performance of laying hens fed LP diets. However, the groups receiving 7 % and 9 % CM exhibited a significant increase in the feed-to-egg ratio (P < 0.05). Additionally, dietary CM supplementation effectively enhanced egg yolk color in a dose-dependent manner (P < 0.05). Intestinal morphology analysis indicated that the 5 % CM group had a higher villus height-to-crypt depth ratio than the LP and 9 % CM groups (P < 0.05), with no significant differences among the other groups. Dietary supplementation with 3 %-7 % CM did not significantly affect serum and jejunal antioxidant capacity, and the 9 % CM group exhibited the highest levels of serum and jejunal malondialdehyde among the groups (P < 0.05). Dietary CM supplementation significantly increased anti-inflammatory cytokines (IL-4 and IL-10) and decreased pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) in the serum and jejunal tissue of laying hens (P < 0.05). Moreover, CM supplementation significantly altered the cecal microbiota composition in laying hens, increasing the abundance of beneficial bacteria, such as Desulfovibrio and Megamonas. Furthermore, dietary CM supplementation significantly decreased serum triglyceride levels; downregulated liver mRNA levels of ACC, FAS, and SREBP-1C/2; and upregulated the mRNA levels of ACOX1, PPAR-α, Apob, and CPT in laying hens fed LP diets. In conclusion, CM supplementation should not exceed 5 % to avoid negative impacts on performance while supporting intestinal health and lipid metabolism.