Manure odour as indicator of hen health and welfare: a study on vaccination challenges in rearing hens

The growing hen number per farm and the decreased availability of sufficiently qualified personnel makes it increasingly difficult to safeguard and control bird health and welfare. This project aims to improve laying hen welfare by early stress-detection based on sensor-aided continuous assessment of predictive health and welfare indicators. During a qualitative multi-stakeholder survey, we identified that currently less than half of laying hen farmers and other poultry experts use odour in health and welfare assessment, and mostly to detect suboptimal intestinal health. To proof the relationship between hen health and odour, we studied the effect of a controlled stressor on manure odour in three commercial flocks of rearing hens. The stressors were salmonella vaccination during the first week of age and at the end of the flock round, and an injection vaccination at twelve weeks of age. In short, fresh manure samples were taken at eight locations on the manure belt on two sampling days before vaccination and on four sampling days after vaccination. Volatile organic compounds (VOC) were extracted from the manure samples by using nitrogen as carrier gas. VOC were captured in sorbent tubes that contained active carbon. The sorbent tubes were connected to a Thermal Desorption Gas Chromatograph Mass Spectrometer to identify and semi-quantify VOC profiles. We compared VOC profiles between hen manure that was produced before and after every vaccination event. Ultimately, the results of this study could aid odour sensor development to continuously detect changes in hen odour as indication of suboptimal health and welfare