Effects of cage stocking density on the production performance, serum biochemistry, immune level, and intestinal morphology of 2 laying hen breeds

This study aimed to determine the effects of different cage stocking densities on the production performance, serum biochemical indices, intestinal morphology and immune levels of Hy-Line Brown and Jinghong laying hens. A total of 432 Hy-Line Brown (n = 216) and Jinghong (n = 216) commercial laying hens were selected and randomly divided into 3 groups according to stocking density: high density (H, 4 birds/cage), medium density (M, 3 birds/cage) and low density (L, 2 birds/cage). In both breeds, the laying rates and Haugh units in the L group were significantly higher than those in the H group (P < 0.05), and the feed-to-egg ratio (feed conversion ratio [FCR]) in the L group was significantly lower than that in the H group (P < 0.05). Additionally, in both breeds, serum triglyceride (TG) activities and corticosterone (CORT) concentrations in the L group were significantly lower than those in the H group. The duodenal villus-to-crypt ratio (VCR) in the L group was significantly higher than that in the H group in both breeds. There were significant interaction effects of breed and stocking density on the laying rate, FCR, Haugh (VH), duodenal VCR and cecal VCR (P < 0.05). Overall, the results of this study indicate that a low stocking density increases the production performance and increases the intestinal mucosal barrier function of laying hens compared to a high stocking density.