Assessment of milk yield losses and subclinical mastitis risk factors using bulk milk somatic cell counts in dairy herds

A prospective study, involving 21 selected dairy farms in north of Tunisia, was conducted to asses the loss of milk production due to high levels bulk tank somatic cell count and to find some relationship between risk factors and subclinical mastitis. We found that the mean of bulk milk somatic cell count was 626 103 cell/ml. Using a simple statistical model, the average loss of milk due to levels bulk tank somatic cell count was 524 kg per cow per year. Using method of mean comparisons, risk factors associated to high levels bulk tank somatic cell count was: Livestock farming risk factors : inadequacy bedding area; inadequacy cleaning bedding and scrapping area. Milking risk factors : washing teat with a shower no adjustable flow and without wipe with individuel towel milk shift work above five per cow-herd; no stripping squirts of milk before milking; milking healthy and mastitis cows at the same time; no teat dipping.