Effects of grazing mixed grass pastures on growth performance, immune responses and intestinal microbiota in free-range Beijing-you chicken

Abstract There is an increasing interest in free-range poultry with the increasing focus on food safety and animal welfare. This study was conducted to evaluate the effects of grazing mixed grass pastures on growth performance, immune responses and intestinal microbiota in free-range laying chickens. 10-wk female Beijing-you chickens were blocked by body weight and randomly assigned to three free-rang systems in poplar plantations for 120 d: forage-removed paddocks with a high stocking density of 5 m2/hen (control, CK); mixed grass pastures with a low stocking density of 6 m2/hen (T1) or with a high stocking density of 5 m2/hen (T2). Intestinal microbial community analysis was performed by 16S rRNA gene sequencing using Illumina MiSeq. The results revealed that no differences (P > 0.05) were found between the three raising systems for body weight and average daily gain. Chickens grazing mixed grass pastures exhibited decreased (P > 0.05) mortality and improved immune responses as evidenced by increased T lymphocytes proliferation (P > 0.05), immunoglobulin A (P > 0.05) and immunoglobulin M concentrations (P