The Determination of some factors whichaffect the longevity of Holsteins Dairy cattle,(Case Study: dairy Economic Institute Quds Razavi)

Longevity expressed as the distance between birth and culling is an economically important trait of dairy cattle for increasing the profitability of dairy management. The aim of the present study is to determine the factors affecting longevity in dairy cows of the farms of Razavi economic organization (RazaviKhorassan, Iran). The dataset consisted of milk production, longevity and health records belonging to 11481 Holstein cows from six herds, culled during 1985 to 2015. Culling reasons were further classified in six groups including reproductive problems, metabolic and digestive disorders, injury and the problems related to dairy cattle welfare, infectious diseases, low and non-economic production and other factors. Farm number one and four (Kenebist) had the lowest and highest longevity with 75.96 and 86.12 months, respectively. From 1985 to 2015, by increasing milk production, the mean of longevity has been decreased. Reproductive problems, metabolic and digestive disorders and infectious diseases were the main reasons of culling with the percentages of 28.49, 24.79 and 22.45 respectively. Results demonstrate again this fact that the dairy cattle management (in this study herd effect) and the high levels of milk production (because of its negative correlation with longevity) are the important factors affecting longevity and should consider them in our breeding programs for dairy cattle lifetime. Key words: Longevity, Reproductive disorders, Days In Milk, Involuntary cull.