ICAR Technical Series no. 7 - Nitra Proc.

de KoningMilk quality is without doubt one of the most important aspects of milkproduction on modern dairy farms. Milk payment systems are based onmilk quality and consumers aspect a high quality level of the milk productsthey buy. Although automatic milking uses more or less the same milkingprinciples as conventional milking, there are some big differences. The24 hour continuous operation of the AM-system requires special cleaningprocedures. Visual control during the milking process is not possible. Alsoteat cleaning cannot be adjusted to the degree of dirtiness. Furthermorethe milking intervals will differ from cow to cow. All these aspects mayinfluence the quality of the milk.Milk qualityand coolingAt the start of automatic milking on commercial dairy farms, it was ageneral assumption that milk quality would be equal or even be improvedafter the change to automatic milking. However, results from commercialfarms indicate that in many cases milk quality is negatively effected(Klungel et al, Van der Vorst). Results are presented in table 1 and show adoubling of the bacterial counts, although the levels are still relatively lowand far within the penalty levels. The cleaning of the milking equipmentand the cooling of the milk seem to be the most important factors regardingthe increase in bacterial counts. Attention should be paid to the hygienicdesign of the milking machine in the AM-system, but research also showedthat complete cleaning and disinfection should be carried out at least threetimes per day. Cleaning is also necessary after milking treated, diseased orfresh calved cows, to prevent contamination of milk. Most AM-systemsalso use a short rinsing between two consecutive milkings, to reduce therisk of transfer of pathogens from cow to cow. However the many cleaningand rinsing cycles in AM-systems will increase the risk of an increasedfreezing point. Special attention should be given to the draining of thesystem after cleaning, the slope of pipe lines and the use of draining valves.Bacterial countsand freezing pointTable 1. Milk quality results for farms before and after introduction of AM-system (Van der Vorst et al.,2000).Dairy farmers First generation Second generation2 timesmilking3 timesmilking Before After Before AfterNumber of farms 60 45 39 39 62 62Bacterial count (*1000/ml) 8 8 8 17 8 12Cell count (* 1000/ml) 181 175 202 203 175 190Freezing point ( o C) -0,520 -0.521 -0.520 -0.517 -0.521 -0.516Free fatty acids (meq/100 gr fat) 0.44 0.54 0.49 0.63 0.41 0.59ICAR Technical Series - No 7135