The overall objective of the ProBioHuhn project is a fundamental contribution to the development of new
strategies for the reduction of disease on organic broiler farms with special consideration of the gut
microbiome. In more detail, the project pursues the following work objectives:
(1) To increase knowledge on disease and therapy frequencies as well as antibiotic resistance in
organic chicken flocks for meat production with respect to three fattening types, i.e. slower growing meat
hybrids, and young cockerels of dual and single purpose lines.
(2) To elucidate the relationship between fattening type and gut microbiome, disease rates and
antibiotic resistance, taking into account animal age, fattening performance, housing environment and
management including feeding, e.g. regarding dietary fibre content.
(3) Derive and evaluate innovative strategies to reduce disease on organic broiler farms, taking into
account on-farm factors as well as factors across farms and stages (feeding, health management, fattening types, etc.).

The three fattening types used in organic chicken husbandry (slower growing meat hybrids, cockerels of
dual and of single purpose lines) will be investigated with regard to animal welfare, particularly to animal
health, and with regard to their intestinal microbiome and antibiotic resistance in the course of the fattening period. For this purpose, a total of 60 flocks on 15 farms (five farms per fattening type, four fattening cycles per farm) will be examined. In each flock the farm documentation concerning animal health and the slaughterhouse records will be investigated. Furthermore, on five consecutive points in time, feed rations will be analysed, animal-related animal welfare indicators (body condition, behaviour, signs of disease) and performance parameters will be recorded. Simultaneously, faecal and environmental samples will be taken that are used to characterise the gut microbiome and detect pathogens and antibiotic resistance genes. The aim is to determine whether there are differences in these measures between the fattening types and different ages, and to what extent this is influenced by farm health management. A particular focus is on the explorative analysis of interactions between housing environment, feeding, age, fattening type and the microbiome, disease rates and antibiotic resistance as well as fattening performance.