Effect of somatic cell count and lactation stage on sheep milk quality

In order to evaluate the effects of mammary health status and lactation phase on the qualitative parameters of ovinemilk, 213 individual milk samples were repeatedly collected from 40 primiparous Sarda ewes on a monthly basis. Yield,physico-chemical characteristics, casein fractions quantitative distribution, somatic cell count (SCC), cheese making propertiesand plasmin-plasminogen activity were determined on each sample. Repeated individual milk SCC were used as amarker of udder health status, allowing the definition of three classes: “Healthy” (H), “Infected” (I) or “Doubtful” (D).Samples were grouped into 4 classes of days in milk (DIM). To evaluate the influence of mammary health status andphase of lactation, a mixed model was performed using the ewe as random effect. Milk physico-chemical parameters wereinfluenced both by the udder health status and by lactation phase. In particular, the udder health status adversely affectedαs1 and β1-casein fractions (Pand 64.60% in “H”, “D” and “I,” respectively. Lactation phase influenced the overall milk composition and technologicalcharacteristics. Plasmin activity was higher in the “I” group than in the others (16.1 vs 11.8 and 11.2 U/ml; Pit significantly (Pexert a detrimental effect on milk quality since they enhance its endogenous proteolytic activity.