Detection of mastitic milk using a gas-sensor array system (electronic nose)

Sammendrag

There is a need for rapid measurement methods for monitoring the hygienic quality of milk in connection with automated milking facilities at the farms. Mastitis is the most common disease in dairy cows. Mastitis can have different aetiology, but is most often associated with bacterial infections.The aim of this project was to test if it is possible to detect mastitis infected milk by use of a commercial gas-sensor array system (electronic nose). The project has been a collaboration between the Swedish University of Agricultural Sciences, DeLaval International AB (Sweden) and MATFORSK. Quarter milk samples were collected from cows with naturally occurring clinical mastitis. Samples were taken from two udder quarters of each cow. In the mastitic cows, mastitic milk samples were taken from the affected quarter and healthy reference milk samples from the opposite hind, or front, quarter. In addition samples from both hind quarters were taken from healthy cows. The results show that mastitic milk can be discriminated from healthy milk by using the electronic noses technology. Also a significant correlation was found between gas-sensor readings and somatic cell counts (r=0,74, p<0,01). Volatile components in the milk were also analysed by dynamic headspace gas chromatography-mass spectrometry. Mastitic milk was characterised by secondary metabolites from bacteria (sulphides, ketones, amines and acids), while both milk from healthy reference quarters in mastitic cows, and milk from healthy cows, was characterised by higher levels of secondary lipid oxidation products (saturated and unsaturated aliphatic aldehydes). The samples used in this study represented all cases of acute clinical mastitis. For a practical application on-line on the milking facility at the farm, however, it is of interest to investigate whether also the earlier stage of mastitis, sub-clinical mastitis, may be detected with this measurement technique.