Changes in Blood Metabolites, Intestinal Microbiota Composition and Gene Expression of 95 Weeks Old Laying Hens Differing in Egg Production and Egg Breaking Strength

SIMPLE SUMMARY: The average cycle of laying hens is prolonged by improving one or more aspects, including genetics, nutrition, and management. Yet, this prolongation needs to go hand-in-hand with laying hens staying vital. Our objective was to explore hen vitality at an age of 95 weeks in association with performance parameters (egg production and breaking strength). To this end, we measured metabolism and disease indicators in blood, microbiota composition and diversity in different gut segments, and the biological activity of the small intestine. We observed that 12% of the hens developed certain aberrations. Additionally, five metabolites were significantly associated to these aberrations, and two metabolites to the performance parameters. In the small intestine we observed that in the production groups the physical barrier function was affected, whereas in the breaking strength group the immune function was affected. Taken together, these data show that hen vitality at later ages can still be improved and we provided data on a molecular level that could be used in future endeavors to improve animal health and welfare. ABSTRACT: Herein, we investigated to what extent molecular phenotypes of the systemic level (blood) and local (intestine) are associated with the performance of laying hens at 95 weeks of age. After the trial had run for 95 weeks, two performance groups were generated, i.e., egg production (PROD) and egg breaking strength (BS). A subset of 21 cages, 116 hens, was measured to indicate the metabolism and disease status. Additionally, a focus group (four cages) was made to perform molecular phenotyping in the intestine. A notifiable observation made during the post-mortem dissection was that approximately 12% of the birds at 95 weeks had developed certain aberrations and/or impairments (denoted as organ morbidity). At the systemic level, we observed five metabolites (γGT, triglycerides, HDL, glucose, and cholesterol) significantly associated to organ morbidity, and only two metabolites (urea and aspartate aminotransferase) to the performance phenotypes. At the local level, when comparing high PROD vs. low PROD, we observed differentially expressed genes involved in cell cycle processes and the extracellular matrix. When comparing high BS vs. low BS differentially, expressed genes were observed mainly involved in immune and cell cycle-related processes. This knowledge is crucial for developing novel strategies of keeping laying hens vital.