Effect of turning out dairy cows to pasture on milk somatic cell count

An increase in milk somatic cell count is often observed in commercial herd s when cows are on pasture during summer. The objective of this study was t o check, in experimental conditions, if this effect is due to the turning o ut to pasture. Three groups of cows were observed for five weeks: 10 cows w ith low somatic cell count (< 100 000 cells/ml) stayed in the cow-shed duri ng the entire study; 10 cows with low somatic cell count and 10 cows with h igh somatic cell count (> 300 000 cells/ml) went to pasture after two weeks in the cow-shed. The measurements were: milk production, chemical composit ion, somatic cell count, pathogens in the milk and plasma markers. Milk pro duction and fat content were higher in cows turned out to pasture than in c ows staying in the cow-shed (+1.4 kg and +3.4 g/kg). No effect of turning o ut to pasture on milk protein content, milk somatic cell count and plasma m arkers level was noticed. In conclusion, the increase in milk somatic cell count observed in summer seems not to be due to the environmental change wh en cows turned out to pasture. Alternative explanations are suggested.