Effects of Dietary Allicin Supplementation on Laying Performance, Egg Quality, Serum Lipid Indices, and Gut Microbiota Composition in Kangle Chickens

Allicin was supplemented into the diet of Kangle chickens, a native Chinese chicken breed, and its effects on laying performance, egg quality, serum lipid indices, and gut microbiota were evaluated. A total of 144 hens at 30 weeks of age with similar body weights were randomly assigned to four groups (CON, AL200, AL400, and AL600), which received a basal diet supplemented with 0 (control), 200, 400, and 600 mg/kg allicin, respectively. The experiment consisted of a 4-day adaptation period followed by a 28-day experimental period. The results showed that, compared with the CON group, average egg weight (AEW) was increased in the AL200 and AL400 groups (p < 0.05), whereas average daily feed intake (ADFI) was reduced in the AL600 group (p < 0.05). Egg shape index (ESI) was increased in all allicin-supplemented groups relative to the CON group (p < 0.05). Regarding lipid profiles, serum total cholesterol (TC) levels were decreased in all allicin-supplemented groups (p < 0.05); serum triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C) concentrations were lower in the AL600 group (p < 0.05); and yolk total cholesterol (YTC) was significantly reduced in the AL400 and AL600 groups (p < 0.05). In addition, the AL600 group had a significantly higher duodenal index (p < 0.05), whereas abdominal fat percentage (AFP) was decreased compared with the CON group (p < 0.05). Gut microbiota analysis revealed that the AL600 group showed significant alterations in alpha diversity indices (p < 0.05). The relative abundance of potentially beneficial bacterial taxa, such as Oscillospiraceae and Romboutsia_B, was significantly increased in this group (p < 0.05). Collectively, these findings suggest that allicin may serve as a promising natural feed additive for increasing egg weight and egg shape index, reducing serum and yolk cholesterol levels, and modulating gut microbiota and predicted metabolic functions in Kangle laying hens.