Automatic milking systems in cheese milk production: potential for improvements

The quality of milk produced by ten farms with an automatic milking system (AMS) and eight farms with a milking parlour (MP) was compared. On each farm, two milk samples – one of evening milk and one taken the following morning were taken monthly in summer, autumn and winter. The samples were analysed for fat, protein, somatic cells, free butyric acid, aerobic mesophilic germs, psychrotrophic germs and anaerobic spores. Other test parameters were freezing point (FP) as well as titratable acidity and methylene blue reduction time after preincubation for 11h at 38 °C and 32 °C respectively. Mean values for AMS and MP milk were significantly different for all parameters except fat and AS (P<0.05). Milk from AMS farms had significantly shorter methylene blue reduction time (38,0 vs. 47,3 min; P<0,001), higher titratable acidity (14,5 vs. 11,4 °SH; P<0,001) and slightly higher counts for aerobic mesophilic germs (6800 vs. 6000 kbE/mL; P<0,001). Levels of free butyric acid were much higher in AMS milk than in MP milk (0,107 vs. 0,061 mmol/L; P<0,001). For all parameters except free butyric acid, farm-to-farm variations were more important than variations between the milking systems.