ASSOCIATIONS BETWEEN HEALTH DISORDERS AND CULLING OF DAIRY-COWS - A REVIEW

Research into the relationships between diseases of cows and culling i n dairy herds is reviewed with emphasis on both results and their fact ors of variation. Tables provide comparisons between studies depending on their designs and their results. Differences between the study pop ulations are outlined. The studied health disorders are extensively re ported and their risks of misclassification are discussed. The other v ariables considered as possible risk factors for culling are reviewed. Some individual characteristics of cows (age, milk production level, reproductive performances) are usually taken into account in the analy ses, whereas the herd effect on the individual risk of culling is poor ly documented. The statistical methods for the analysis of health diso rders as risk factors for culling are summarized. Certain health disor ders (dystocia, mastitis) increase the risk of culling regardless of t he production systems considered. However, for other health disorders (milk fever, metritis, cystic ovaries, retained placenta, locomotor di sorders), contradictory results are reported. These discrepancies may result from either actual differences in the production systems studie d or differences in methodologies used. The interest of further studie s investigating especially the herd effect on the individual risk of c ulling is displayed.