The incidence of many of the most common diseases in dairy cattle has been proven to be highest during the time closest to calving. It is possible that the current breeding strategy with 12 month calving intervals increases the risk for disease in dairy cattle, which is problematic concerning both animal welfare and for economic reasons. The economic incentives behind a calving interval of 12 to 13 months have mainly been based on milk- and feed- costs and no costs due to diseases or fertility disturbances have been included.The aim of this study was to see if a lengthening of the calving interval would result in lower disease frequency. The hypothesis is that cows with a planned calving interval of 15 months have a lower disease incidence than cows with a calving interval of 12 months due to less number of calvings. Therefore the difference in disease frequency should be larger when compared over a long period of time, such as over lifetime, since cows with a longer calving interval experience fewer calvings.The study was performed between August 17th, 1994, and January 24th, 2007.

Ett stort antal kor slås idag ut innan de hunnit uppnå sin fulla mjölkproduktionspotential. En svensk ko t.ex. lever i medeltal 2,44 laktationer eller ca fem år. Detta är både ett djurvälfärdsproblem och något som kan medföra ekonomiska konsekvenser för lantbrukaren. Syftet med den här litteraturstudien var att sammanställa faktorer som har visat sig påverka utslagning av mjölkkor. De främsta orsakerna till ofrivillig utslagning var nedsatt fruktsamhet (17-36,7 %), juversjukdomar (14-30 %) samt ben- och klövlidanden (3,8-16,7 %).