Disequilibrium feeding pattern more consistent with egg-laying physiology improves eggshell quality of laying hens...

Disequilibrium feeding pattern, as a new feeding technique, more suitable for egg-laying physiology, was feeding two-thirds diet to hens after 14:00 every day without modifying diet nutrient levels and changing daily feed rationing, to better meet calcium requirement of hens during eggshell formation. To verifying its application on eggshell quality of aged laying hens, 288 Hy-line laying hens (average body weight 2.03 ± 0.09 kg) at the age of 70 wk, as experimental birds, were randomly allocated into four groups (6 replicates/group, 12 hens/replicate); the experiment for eight weeks used a 2 × 2 arrangement with the factors- dietary calcium level (3.5% and 3.0%) and feeding pattern (equilibrium and disequilibrium), and univariate general linear model to analyze the main effects. The disequilibrium feeding decreased average daily feed intake (ADFI) (P < 0.001) and feed conversion ratio (FCR) (P < 0.001) of hens from the age of 71 to 74 wk. Low dietary calcium level decreased eggshell proportion (P = 0.007), eggshell strength (P = 0.046), and average eggshell thickness (P = 0.025) of hens at the age of 74 wk. Noticeably, the ultrastructure measurement of equatorial section confirmed that disequilibrium feeding increased eggshell thickness of hens at the age of 78 wk by increasing palisade layer thickness (P = 0.013) and mammillae layer thickness (P = 0.018). Disequilibrium feeding improved eggshell ultrastructure, possibly by increasing dietary calcium utilization. Decreased calcium excretion in feces during the daytime and increased calcium deposition in bones at night showed a positive correlation with increased bone mineral density at night by disequilibrium feeding (P < 0.05). These results were attributed to modified intestinal integrity, improved intestinal permeability and calcium absorption, which occurred through the increased thickness of duodenal mucus layer (P = 0.006), up-regulated mRNA expression of intestinal permeability-related genes occludin (P = 0.031) and MUC-2 (P = 0.002), and some involved intestinal bacteria such as decreased Parabacteroides (P = 0.007) and increased Lachnoclostridium (P = 0.017) being beneficial to calcium absorption strength and mucosal inflammation. Disequilibrium feeding pattern could improve eggshell quality, which may provide a protection for suitable reduction in dietary calcium level in aged laying hens, not affecting eggshell quality, but reducing intestinal burden and improving welfare.