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

Abstract

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