ABSTRACT
The prevalence of sub-clinical ketosis and its predisposing factors were assessed in three dairy farms with different sizes [large, medium, small] and different facilities, and with constant management routines. Eighty-one cows within the first two months of lactation were sampled for blood. The concentrations of beta-hydroxybutyrate and glucose were determined in blood serum. Rations were analyzed for dry matter, crude protein, crude fat, NDF, fNDF and NFC. The housing conditions of the cows were also assessed. The prevalence of sub-clinical ketosis [beta-hydroxybutyrate > 1000 micromole/lit] was 7.7%, 70.6% and 87.5% in the large, the medium and the small farm, respectively. The disease prevalence was 42% in the sum of the three farms. The primary dietary insufficiencies [especially in NDF, fNDF and dry matter] were diagnosed to be some of the most important reasons of the high prevalence of the disease. However, reformulating of the rations, without considering the infrastructure of the farms and the interactions among nutrition, management and environment, would not have a reasonable effect on prevention of sub-clinical ketosis