title: Helminth infection is associated with hen mortality in Danish organic egg production.
abstract: The aim of this study was to investigate whether two highly prevalent helminth infections (Ascaridia galli and Heterakis species) are associated with an increased mortality rate for hens at the peak of lay. An observational event study with 11 farms was conducted between 2012 and 2013, with weekly mortality recordings and grouping of the farms into low-infected with A galli and Heterakis species (0-200 epg of faeces) or high-infected (over 200 epg of faeces). Survival analysis was performed using a discrete time proportional hazards model. The difference between the hazard functions for low-infected farms and high-infected farms in either summer (August to September) or winter (January to March) were analysed. No statistically significant associations were found between the mortality rate in winter and summer in low-infected farms. However, the mortality rate was doubled for hens from high-infected farms observed in the summer season compared with hens from low-infected farms (winter and summer), whereas high-infected farms observed in the winter did not have a significant association between mortality rate and season compared with low-infected farms (summer and winter). The results suggest that the mortality in organic egg production may be reduced by measures to control A galli and Heterakis species infections.
authors.affiliation: Department of Animal Science, Faculty of Science and Technology, Aarhus University. Blichers Allé 20, P. O. Box 50, DK-8830 Tjele, Denmark.
authors.forename: L K
authors.initials: LK
authors.lastname: Hinrichsen
authors.affiliation: Department of Mathematics, Faculty of Science and Technology, Aarhus University, Ny Munkegade 118, DK-8000 Aarhus, Denmark.
authors.forename: R
authors.initials: R
authors.lastname: Labouriau
authors.affiliation: Department of Animal Science, Faculty of Science and Technology, Aarhus University. Blichers Allé 20, P. O. Box 50, DK-8830 Tjele, Denmark.
authors.forename: R M
authors.initials: RM
authors.lastname: Engberg
authors.affiliation: Farm Animal Behaviour and Husbandry Section, University of Kassel, Nordbahnhofstraße 1a, D-37213 Witzenhausen, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Knierim
authors.affiliation: Department of Animal Science, Faculty of Science and Technology, Aarhus University. Blichers Allé 20, P. O. Box 50, DK-8830 Tjele, Denmark.
authors.forename: J T
authors.initials: JT
authors.lastname: Sørensen
mesh_terms: D000818:Animals; D001197:Ascaridia / Q000302:isolation & purification; D002645:Chickens; D003718:Denmark / Q000453:epidemiology; D004531:Eggs; D005243:Feces / Q000469:parasitology; D005260:Female; D058870:Food, Organic; D006374:Helminthiasis, Animal / Q000401:mortality* / Q000469:parasitology; D011201:Poultry Diseases / Q000401:mortality* / Q000469:parasitology
keywords: Eggs; Endoparasites; mortality