A MULTIVARIATE INDEXING SYSTEM FOR HYGIENE IN RELATION TO THE RISK OF MYCOPLASMA-GALLISEPTICUM INFECTION IN CHICKENS

An indexing system for hygiene variables was developed using data collected on chicken flocks in Southern California. Thirteen risk factors related to hygiene were analyzed with stepwise multiple logistic regression to develop a model combining information on factors significantly associated with the risk of Mycoplasma gallisepticum infection. The index was constructed from variables found in the model from random subsamples of 70 and 50% of the study population and was cross-validated on the remaining 30 and 50% of the samples respectively. The index correctly identified 91 and 90% of the infected flocks in the remaining 30 and 50% of the subsamples respectively. © 1990.